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The Iranian Journal of Plant Physiology https://ijpp.saveh.iau.ir/ is a reputable journal that publishes original research articles, reviews, and short communications related to plant physiology and biochemistry. As of my knowledge cutoff date of September 2021, the journal was indexed in Scopus and had a Q3 ranking. One advantage of this journal for non-Iranian authors is that it offers free publication for them, which can be beneficial for researchers who may otherwise face financial barriers to publishing their work. Additionally, the journal has a relatively quick initial decision time, with authors typically receiving a decision within a few days of submission. However, the review process may take up to 4 weeks, which is a standard timeline for many journals. Overall, the Iranian Journal of Plant Physiology can be a good option for researchers in the field of plant physiology and biochemistry, particularly for those who are looking for a journal with a relatively quick decision time and no publication fees for non-Iranian authors.

1. Water is essential for numerous metabolic functions in plants and its loss can affect all aspects of plant growth and survival. 2. Acer velutinum is a fast-growing species of hardwood tree that is commonly used in afforestation and reforestation. 3. The impact of water deficit on the growth, biomass, pigment contents, relative water content, and osmolytes such as free proline, soluble protein, and soluble sugar were studied in this research. 4. The antioxidative enzymes including guaiacol peroxidase and catalase were also analyzed to identify the protective mechanisms related to drought resistance. 5. One-year-old seedlings were exposed to four drought treatments (100%, 75%, 50%, and 25% of the field capacity). 6. The drought treatments had a negative impact on A. velutinum growth, as exhibited by reduced plant height, basal diameter, and biomass. 7. Drought stress decreased relative water content and chlorophyll content while increasing electrolyte leakage, osmotic substances, and catalase and peroxidase activities. 8. The findings showed that A. velutinum seedlings have the capacity to adapt to water deficiency and can be recommended for afforestation and reforestation. 9. Antioxidant enzymes, biomass, and water deficit are important keywords related to this study.

Extreme climatic phenomena such as heat waves, heavy rainfall and prolonged droughts are one of the main problems associated with ongoing climate change. The global increase in extreme rainfalls associated with summer heatwaves are projected to increase in amplitude and frequency in the near future. However, the consequences of such extreme events on lichens are largely unknown. The aim was to determine the effect of heat stress on the physiology of lichen Cetraria aculeata in a metabolically active state and to verify whether strongly melanised thalli are more resistant than poorly melanised thalli. In the present study, melanin was extracted from C. aculeata for the first time. Our study showed that the critical temperature for metabolism is around 35 °C. Both symbiotic partners responded to heat stress, manifested by the decreased maximum quantum yield of PSII photochemistry, high level of cell membrane damage, increased membrane lipid peroxidation and decreased dehydrogenase activity. Highly melanised thalli were more sensitive to heat stress, which excludes the role of melanins as compounds protecting against heat stress. Therefore, mycobiont melanisation imposes a trade-off between protection against UV and avoidance of damage caused by high temperature. It can be concluded that heavy rainfall during high temperatures may significantly deteriorate the physiological condition of melanised thalli. However, the level of membrane lipid peroxidation in melanised thalli decreased over time after exposure, suggesting greater efficiency of antioxidant defence mechanisms. Given the ongoing climate changes, many lichen species may require a great deal of plasticity to maintain their physiological state at a level that ensures their survival.

In their natural environment, plants are often exposed to a wide array of stressful conditions that frequently occur in combination, and which can cause complex responses. There is a lack of research into many of these combinations, including low temperature and waterlogging, which is relevant to early spring conditions in northern climates around the world. The current study focused on examining this stress combination, using Nicotiana tabacum as a model system. Tobacco plants were exposed to this combination for seven days, followed by a seven-day recovery period, and the effects on the physiology, the photosynthetic apparatus and metabolism were examined. It was determined that a low oxygen 'escape' strategy, characterized by continued rapid growth dominated in plants that were waterlogged at optimal growth temperatures. In contrast, exposure to low temperature induced a 'quiescence' strategy, causing decreased rates of photosynthesis and growth, regardless of whether a plant was waterlogged or not. Once the stresses were removed and plants were allowed to recover, plants exposed to low temperatures exhibited a more robust ability to recover, even when they had also been exposed to waterlogging stress. As such, it was concluded that simultaneous exposure to low temperature and waterlogging stresses is not more damaging than exposure to low temperature stress alone. Cannabis sativa is a dioecious plant known for the accumulation of secondary metabolites (cannabinoids) with known psychoactive and medicinal properties. Until recently, cultivation and usage of this plant was illegal and thus, much of its biology remains understudied. The second part of this thesis focuses on some of the first steps taken to study how cannabis responds to stress, including a detailed review of the recent literature on this topic. The genetic basis of stress resilience in this plant was also examined by characterizing the antioxidant gene family. These enzymes scavenge reactive oxygen species (ROS), to maintain healthy levels of these molecules. Under stress however, ROS can accumulate at high and damaging concentrations. Subsequently, increased accumulation and activity of antioxidant enzymes to manage ROS is a well-known hallmark of plant stress. It has been determined that H₂O₂ (a major plant ROS) is a by-product of cannabinoid synthesis. Accumulation of high cannabinoid levels has been associated with decreases in biomass and increased tissue damage. This may potentially be attributed to increased ROS levels due to cannabinoid synthesis. A genome-wide identification of antioxidant genes in two published C. sativa genomes was conducted. This screen identified ~40 antioxidant genes in both cannabis strains, ~25% of which localized to the female X chromosome. The increased abundance of antioxidant genes on the X chromosome may be a mechanism to increase antioxidant amounts in female plants that naturally accumulate high cannabinoid levels, and therefore produce increased ROS. Thus, the future selection of cannabis strains with increased antioxidant capacity may lead to development of more productive cultivars.

Many studies proposed the use of stable carbon isotope ratio (δ13C) as a predictor of abiotic stresses in plants, considering only drought and nitrogen deficiency without further investigating the impact of other nutrient deficiencies, that is, phosphorus (P) and/or iron (Fe) deficiencies. To fill this knowledge gap, we assessed the δ13C of barley (Hordeum vulgare L.), cucumber (Cucumis sativus L.), maize (Zea mays L.), and tomato (Solanum lycopersicon L.) plants suffering from P, Fe, and combined P/Fe deficiencies during a two-week period using an isotope-ratio mass spectrometer. Simultaneously, plant physiological status was monitored with an infra-red gas analyzer. Results show clear contrasting time-, treatment-, species-, and tissue-specific variations. Furthermore, physiological parameters showed limited correlation with δ13C shifts, highlighting that the plants' δ13C, does not depend solely on photosynthetic carbon isotope fractionation/discrimination (Δ). Hence, the use of δ13C as a predictor is highly discouraged due to its inability to detect and discern different nutrient stresses, especially when combined stresses are present.

Blueberry (Vaccinium ashei) is a popular fruit due to its high anthocyanin content. This study aimed to analyze the transcriptome profile of V. ashei cv. ‘Brightwell’ fruits at different stages of development. A total of 314.26 GB of clean data were obtained and de novo assembled into 254 196 unigenes. In comparisons between the early and late stages of fruit ripening, 27 genes (including PAL, CHS, F3H, F3′H, F3′5′H, LDOX, etc.) were found to cover the main steps in the anthocyanin biosynthesis pathway. Most of these genes were highly expressed in the late stage of fruit development, suggesting that anthocyanins mainly accumulate in the late stage. During the late stage of fruit development, most structural and regulatory genes such as F3′5′H and F3′H, which are involved in the anthocyanin biosynthetic pathway, were upregulated, causing the fruit to turn blue. Decreased expression of a large number of chloroplast-related genes during the fruit ripening period could explain why the green fruit color fades over time. Additionally, abscisic acid and ethylene may play positive roles in promoting fruit ripening and anthocyanin accumulation. This research reveals the transcriptomic characteristics of immature and mature fruits and enhances our understanding of the molecular mechanisms of anthocyanin biosynthesis and accumulation in blueberry fruit.

A greenhouse study was conducted to determine the effects of foliar applications of magnetized, chelated liquid iron fertilizer for increasing the drought tolerance of two legumes. Study objectives were to determine the drought tolerance effects of four treatments on foliar gas exchange, soil moisture, and plant growth for velvet bean (Mucuns pruriens) and soybean (Gylcine max) plants. The four foliage treatments included applications with chelated liquid iron fertilizer (2.5 and 5%) with a conventional boom sprayer, with and without magnets in the spray lines. Physiological measurements were collected before foliar treatments and again after a 24-day deficit irrigation schedule. Physicochemical water properties were measured for each of the foliar treatments. Photosynthesis rates were 5.98, 2.04 and 3.19 µmol/m2/s for the control, non-magnetized and magnetized fertilizer treatments (2.5%), respectively, after completing the deficit irrigation schedule. Instantaneous water use efficiency (IWUE) was 0.60, 0.28 and 1.02 for the control, non-magnetized and magnetized fertilizer treatments (2.5%), respectively, after completing the deficit irrigation schedule. Photosynthesis and IWUE increased 56 and 263% for the magnetized fertilizer treatment (2.5%) compared to the non-magnetized foliar treatment, when averaged across both legume species. Photosynthesis and IWUE increased as electrical conductivity increased and oxidation reduction potential (ORP) decreased in absolute terms. A single foliar application resulted in aberrant physiological responses that are contrary to very widely held plant defense theories involving abiotic stressors. The single application improved the photosynthesis and water use efficiency for water stressed legumes emphasizing the need to better understand the relationships between water quality, plant bioenergetics, and stress physiology. Improved drought tolerance in row crops such as dry beans and soybeans, with a single magnetized fertilizer application, would be cost effective and easily adapted into current cropping systems. Interactions among physicochemical water properties, bioenergetics, plant metabolism, and crop stress physiology need to be further investigated in order to improve the quality of irrigation water to enhance drought tolerance of field crops.

Seeds vigor defined in the laboratory does not always reflect the final quality of seedlings produced under nursery conditions or even their survival in plantations. So, we studied the influence of Cedrela fissilis seed storage conditions on its emergence and the morphological quality of produced seedlings. Seeds were collected in October/2011, benefited, conditioned in closed glasses, and stored in three environments for a period of 515 days. Treatments consisted of: I - seedlings produced from seeds without storage (control); II - seedlings produced from seeds stored in a dry chamber; III - seedlings produced from seeds stored in a humid chamber; IV - Seedlings produced from seeds stored in an uncontrolled environment (laboratory). Sowing was performed in 50 cm³ plastic tubes filled with decomposed pinus bark and coconut fiber (50/50 v/v) and packed in a glasshouse. The study analyzed the percentage of seedlings emergence, mean seedlings emergence time, stem diameter, total height, the ratio between total height and stem diameter, shoot length, root length, total, root and shoot dry biomass, and Dickson quality index. Seed storage proved to be a negative factor for the emergence and vigor of C. fissilis seedlings, regardless of the storage environment. In addition, seeds vigor is a preponderant factor to increase seedlings' morphological quality, such as stem diameter and height.

Volatiles from herbivore-infested plants function as a chemical warning of future herbivory for neighboring plants. (Z)-3-Hexenol emitted from tomato plants infested by common cutworms is taken up by uninfested plants and converted to (Z)-3-hexenyl β-vicianoside (HexVic). Here we show that a wild tomato species (Solanum pennellii) shows limited HexVic accumulation compared to a domesticated tomato species (Solanum lycopersicum) after (Z)-3-hexenol exposure. Common cutworms grow better on an introgression line containing an S. pennellii chromosome 11 segment that impairs HexVic accumulation, suggesting that (Z)-3-hexenol diglycosylation is involved in the defense of tomato against herbivory. We finally reveal that HexVic accumulation is genetically associated with a uridine diphosphate-glycosyltransferase (UGT) gene cluster that harbors UGT91R1 on chromosome 11. Biochemical and transgenic analyses of UGT91R1 show that it preferentially catalyzes (Z)-3-hexenyl β-D-glucopyranoside arabinosylation to produce HexVic in planta., 植物間コミュニケーションの仕組みを解明 --受容した香りを防御物質に変える遺伝子発見--. 京都大学プレスリリース. 2023-02-28.

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Lucerne (Medicago sativa) is a perennial crop with a deep taproot system penetrating several metres down the soil profile and thus can be integrated into crop rotations to reduce watertable recharge to ameliorate saline and waterlogged sites and to redress the environmental threat of rising saline watertables. Despite this fact, not much is known about specific mechanisms mediating adaptive responses of luceme to waterlogging and salinity stresses. One of the aims of this project was to provide such information. Also, for luceme's ameliorative properties to be fully exploited, tolerant genotypes need to be identified. Keeping in mind a high degree of genotypic variation within luceme in terms of its tolerance to waterlogging and salinity, another aim of this study was to identify physiological indicators, which might become useful screening tools for tolerance to the stresses of waterlogging and salinity. Physiological responses to these abiotic stresses were characterized under a variety of conditions using photosystem (PS) II photochemistry, leaf gas exchange, pigment concentrations, biomass, nutrient dynamics and mesophyll cell anatomy, to find the most appropriate method for screening for stress tolerance in luceme. The practical application of this work is its use as suggested screening tools for the ACIAR funded project Lucerne for Animal Production and the Environment, (collaboration between Australia and China). Significant effects of waterlogging were measured across all genotypes. Chlorophyll fluorescence variation became apparent on day 7 of stress and therefore appeared to be a useful, early non-destructive indicator of waterlogging stress tolerance. Recovery dynamics following waterlogging were investigated in four genotypes by studying PS II photochemistry and relating these to nutrient concentration changes. Nutrient concentrations at the end of recovery regained pre-stress values and PSII photochemistry also largely recovered. Preliminary studies on the concurrent stresses of waterlogging and salinity measuring chlorophyll fluorescence on excised, waterlogged leaves exposed to varying concentrations of salinity indicated a significantly greater stress response than salinity on its own. Germination trials on ten genotypes and varying salinity levels pointed to a genotypic response to salinity, but correlations with parameters measured at later stages of plant ontogeny were not evident. Salinity effects on plant growth characteristics, pigment and nutrient composition, leaf sap osmolality, changes in anatomical and electrophysiological characteristics of leaf mesophyll, and net ion fluxes in roots of six luceme genotypes were investigated. Waterlogging caused a marked reduction in photosynthetic capacity as measured with `CO_2` assimilation rate and chlorophyll fluorescence. A wide range of Fv/Fm values (maximal photosynthetic capacity) was recorded within stressed cultivars, suggesting some scope in discovering more tolerant individuals. However, only minor genotypic differences were detected. This might be due to luceme being a highly cross-pollinating species, as individual luceme populations consist largely of a heterogeneous mixture of genetically heterozygous individuals. This fact seems to overshadow most of the differences between cultivars. Results of the salinity experiment suggest that different luceme genotypes use contrasting strategies to avoid toxic effects of sodium on cell metabolism. Sodium exclusion seemed to be used by at least one of the cultivars under investigation, whereas sodium inclusion and subsequent sequestering into vacuoles appeared to be used by other tolerant genotypes. When selecting genotypes for salt tolerance, it is important to consider the possibility of these different adaptation mechanisms being at play. Overall, this study suggests that multiple traits are involved in determining salt and waterlogging tolerance in lucerne. The problem is additionally exacerbated by a high degree of genetic variability within he!erozygous luceme populations; therefore screening for luceme improvement should rely on several, not just not one selection criteria. Ideally these criteria should be attributable to several physiological mechanisms involved. In addition, it appears that such screening should also be aimed at searching for outstanding individuals within a population, not only at comparing genotypes from a genetically diverse and promising pool of potentially tolerant luceme germplasm.

Eucalyptus globulus Labill. and E. nitens (Deane and Maiden) Maiden are the predominant hardwood plantation species in southern Australia. This thesis describes some physiological strategies exhibited by these species in response to drought as a means of determining their suitability for establishment on water limited sites. To this end a 2 ha experimental plantation was established on a low rainfall site (ca. 5 1 5 mm a-1) in August 1990. The plantation was divided into irrigated and rainfed blocks so that the effects of soil drought could be separated from those of diurnal and seasonal climatic variation. Between November 1991 and April 1993 pre-dawn leaf water potential (˜í¬Æmax) was significantly lower in the rainfed than the irrigated treatment for six defined periods or stress cycles. At the end of this period, when ˜í¬Æmax was -2.37 and -2.34 MPa in the rainfed E. globulus and E. nitens respectively, leaf osmotic potential and bulk elastic modulus were still not significantly affected by water stress. At this time a significant interspecific difference was evident in the shape of the desorption isotherms. In the region of positive turgor the mean slope of these relationships was significantly greater in E. nitens (14.5 MPa) than E. globulus (9.3 MPa) resulting in turgor loss at a significantly higher relative water content in E. nitens (0. 86) than E. globulus (0. 79). This interspecific difference in leaf water relations was independent of soil water status. Allometric relationships between leaf area and sapwood area were developed by destructive sampling in July 1992 and July 1993. These relationships were used with monthly growth data to plot the course of leaf area index (L *) between August 1991 and April 1993. L* was significantly lower in E. nitens than E.globulus throughout the study and was significantly reduced by water stress after November 1992. During the 1992/93 growing season the L* of the rainfed E.globulus increased rapidly after rewatering, resulting in a stepped pattern of leaf area development which was not observed in E. nitens. At the end of the experiment, in April 1993 , L* of the irrigated and rainfed treatments were, respectively, 8.3 and 6.1 in E. globulus and 6.9 and 4.3 in E. nitens. Daily maximum stomatal conductance of both E. globulus and E. nitens was significantly reduced when ˜í¬Æmax was

There are a number of putative tryptophan-dependent pathways leading to the bioactive auxin, indole-3-acetic acid (IAA) in plants, although none of these is fully characterised in terms of the isolation of genes for enzymatic reactions, and identification and quantification of precursor compounds. Herein, the tryptamine pathway (tryptophan ‚Äö- tryptamine - indole-3-acetaldehyde - IAA), the indole-3-pyruvic acid pathway (tryptophan - indole-3-pyruvic acid- IAA) and the indoleacetamide pathway (tryptophan ‚Äö- indoleacetamide - IAA) to IAA are examined in Pisum sativum (pea) using a compound-based approach, detecting potential precursors by gas chromatography/tandem-mass spectrometry (GC/MS/MS) and ultra performance liquid chromatography/mass spectrometry (UPLC/MS), in order to complement the genetic findings of others. Synthesised deuterated forms of the intermediates involved have been used to quantify the endogenous compounds, and to investigate their metabolic fates. Methods for the isolation and quantification of the following compounds were devised and tested. Tryptophan, tryptamine, indole-3-acetaldehyde (IAAld), indoleacetamide, indole-3-ethanol (IEt) and IAA were detected as endogenous constituents, whereas indole-3-acetaldoxime and one of its products, indole-3-acetonitrile, were not detected. Metabolism experiments indicated that the tryptamine pathway to IAA in pea roots proceeds in the sequence tryptophan ‚Äö- tryptamine ‚Äö- IAAld ‚Äö- IAA, with IEt as a side-branch product of IAAld. The endogenous levels of IAA precursors, along with their abundance in tissue types, of a low-auxin mutant (bushy) have also been studied in order to characterise the mutation, and to assess the involvement of different IAA biosynthesis pathways. The effects of wounding, a synthetic auxin and an inhibitor of auxin action on the regulation of the biosynthesis pathways have also been studied. It appears that the tryptamine pathway is operative in pea roots; however, it cannot be ruled out that other tryptophan-dependent pathways to IAA are also operative, nor can we rule out the possibility of a tryptophan-independent pathway operating in these organs.

Xero- and scleromorphic adaptations are obviously shown by Australian plants, in response to the Australian climate and edaphic factors. Since these adaptations overlap, there are problems separating the two. Some qualitative hypotheses about the distinction between xero- and scleromorphic characters have been proposed. This research is an effort to quantitatively determine xeromorphic characters in some members of the Proteaceae, in order to elaborate upon some of the existing hypotheses about these characters. Twenty three species of Banksia, 16 species of Grevillea and 6 species of Orites were sectioned and observed under the light micrscope and measurements were made of the stomata! depressions, margin recurvations, cuticle thickness and hair dimensions. Cuticle peels were made in order to count the number of stomates and hairs on the leaf surface. From the characters measured the following were calculated: the depression index (Id), recurved margin index (Irm), epidermis index (le), hair. index _ (Ih) and cuticle components. The sum totals of the calculations were called the stomata! protection component (Spc). These data were then analysed using an analysis of variance with five replicates per species, in order to investigate whether there were any differences in characters determined .among species observed. Every index calculated (Id, Irm, Ih, le) and the cuticle components were analysed separately, with the aim of determining the intensity of the association between the characters observed and the minimum of the range of habitat annual rainfall, the maximum of the range ·of habitat annual temperature, the maximum of the range of habitat daily radiation and the maximum of the range of maximum daily wind run. An analysis of correlation was applied to these data. A similar method was applied for observations on juvenile and adult leaves. On the basis of these results the possible evolution of Banksia is reconstructed. Results showed that in Banksia species stomata! depression seems to have an important role protecting the stomates from the effect of habitat climatic factors, especially from temperature and radiation effects. The presence of recurved margins and hairs, however, were not as important as stomata! depressions. In Grevillea species, cuticle characters had a significant role in stomata! protection, particularly the stomata! and lower epidermis cuticle. A _contradictory finding to that of Banksia in this genus was that stomata! depression did not contribute to the stomata! depression. In comparison to the two genera already discussed, Orites was quite different. However, the hairs had a significant contribution in protecting stomates from temperature and radiation effects. - The phenomenon of leaf transition from juvenile to adult in some species observed showed some performance similarities to plants grown in harsh environments. Banksia blechnifolia leaves exhibited more intense stomata! depression and denser leaf hairs in adult leaves. It was assumed that these structures increased stomatal protection from excessive radiation. Similar growing phenomena were displayed by leaves of Grevillea pyramidalis. Stomata! depression in this species developed from being not present to being present and then deepened in later leaves. In addition, leaf hairs showed a gradual alteration in density from seedling through juvenile and adult leaves. However, leaves of B. marginata did not show the presence of stomata! depressions either in juvenile or adult stage. The leaf hairs, however, exhibited similar phenomena to those found in B. blechnifolia and G. pyramidalis. The results suggest that stomatal depression, margin recurvation, leaf hairs and cuticle characters increase stomata! protection either individually or collectively. It thus can be concluded that there is a possibility that these characters are xeromorphic when expressed by Banksia, Grevillea and Orites species .

The vegetation of the Windmill Islands oasis, Wilkes Land, continental Antarctica is dominated by lichens. Aspects of the ecology and physiology of lichens were studied during three summers and a winter period on the well vegetated Clark and Bailey Peninsulas in an attempt to explain patterns in lichen distribution. Most studies were done at a knoll on Clark Peninsula. This knoll has an extensive range of substratum nutrient levels and a variety of microhabitats, resulting in a variety of niches in a small area. At this site 29 identifiable species of lichen occur in seven sociations, most dominated in varying degrees by the macrolichens Pseudephebe minuscula, Umbilicaria decussata, Usnea sphacelata and Usnea antarctica. The crustose lichen Buellia frigida dominates sites on exposed boulders and a separate suite of species inhabits dead and dying moss. There are a suite of species which are restricted to sites with high nutrient levels, although the distribution of the dominant species is relatively insensitive to substratum nutrition. Exposure limits all species to various extents, with all lichens being intolerant of late-lying snow. The nitrogen and phosphate content of lichen thalli is clearly related to that of the substratum on which they are growing. Monthly sampling of Usnea sphacelata and Umbilicaria decussata from eight sites identified a consistent trend in thallus nitrogen content with %N increasing throughout the winter and then dropping sharply with the onset of the melt and increasing during the summer. Lichen integrity during the middle of winter and before and after an unusual winter event were assessed by investigating the distribution of mineral nutrients within the lichen thallus. Although the distribution of minerals in the thalli differed between species and sites there was no effect of month and therefore the unseasonal rewetting and subsequent refreezing had little effect on membrane integrity. The most important time for lichen photosynthetic activity was early summer from late October to early December. The increasing temperatures and insolation at this time lead to a great deal of snow melt and hence an increase in the availability of free water. Humidity was therefore high so that activation of photosynthesis was possible through water vapour uptake alone. During the bulk of the summer lichens are photosynthetically inactive. At this time the air is too dry for lichens to absorb sufficient water from the atmosphere to initiate photosynthesis and hence they rely on direct moistening from summer snow falls and run off. The photosynthesis of the major species as a function of thallus water content was related to their observed distribution patterns. Together, substratum nutrient levels, microclimate and photosynthetic characteristics of species can describe a great deal of the observed distribution patterns of lichens in the Windmill Islands.

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Certain plants have found ways to tolerate undesirable, stressful environments. Plants that tolerate stressful and non-stressful conditions can respond by altering their morphology, phenology, and physiology to survive. Serpentine soil often contains a high number of heavy metals and low amount of calcium, creating a stressful soil environment that is not ideal for many plants. We looked at three petaloid monocots in closely related orders, Calochortus amibilis, Dichelostemma capitatus, and Triteleia laxa, that can tolerate serpentine soils and non-serpentine soils. For each plant, we used a t-test to see how serpentine affects morphological (height, leaf length, leaf width, and total floral output), phenological (#flowers + #fruits/total floral output), and physiological (total stomatal density and xylem area) characteristics. In serpentine soils, T. laxa responded by having shorter height, smaller leaf lengths, less floral output, and more stomatal density. C. amibilis only differentiated in having wider leaves when growing in serpentine soil. D. capitatus had a marginally later phenology on serpentine but didn’t differ otherwise. All these plants had different responses to tolerating serpentine soils, even though they are all in closely related orders. This study shows that plants with similar body plans could find separate ways to tolerate the same stressful environment., Volume 7, Issue 1

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Nitrogen-fixing bacteria, collectively referred to as rhizobia, are able to trigger the organogenesis of novel organs on legumes, called nodules. The initiation and development of nodules requires a complex signal exchange involving both plant and bacterial compounds. Phytohormones have been implicated in this process, although in many cases direct evidence is lacking. In the work reported here, the root and nodulation phenotypes of various mutant lines of Pisum sativum L. are characterized, including those having alterations in their phytohormone levels and/or perception, and a homeotic mutant. Root systems having similar or elevated GA levels compared with that of their wild type developed wild type numbers of nodules, whereas those deficient in gibberellins or brassinosteroids exhibited reduced nodulation. Gibberellin application or grafting to a wild type root or shoot restored the nodule number of a gibberellin-deficient mutant to that of its wild type. In contrast, the shoot controlled the number of nodules that formed in graft combinations of a brassinosteroid-deficient mutant and its wild type. Interestingly, a strong correlation between nodule and lateral root numbers was observed in all lines assessed, consistent with a possible overlap in the early developmental pathways of the two organs. Double mutants possessing the na mutation, which results in severe GAdeficiency, and the sln mutation, which results in elevated seedling GA levels, displayed abnormal nodules and a reduced capacity to autoregulate their nodule numbers. Constitutive GA signalling mutants also produced significantly fewer nodules than their wild type. However, these nodules were normal in appearance, and significantly greater in number compared with that of na plants, regardless of whether or not they also possessed the na mutation. This indicates that intact GA signalling pathways are required for nodule development. Additional double mutants were created by crossing na with one of three independent mutations, nod3, sym28, and sym29/nark/har-1, that result in a plants inability to regulate its nodule number. Double mutant segregates from each of these crosses formed significantly more nodules than na, but these structures maintained the aberrant na nodule morphology. A significant increase in nodule numbers was also observed on na following treatment with an ethylene biosynthesis inhibitor, but these nodules were also aberrant. These findings suggest that GAs are required for late nodule development and that ethylene has a role in nodule initiation. The histology of na nodules further supported a role for gibberellins late in nodule development as the cells of the infected zone failed to enlarge. The nodulation phenotype of the homeotic mutant, cochleata, which has stipules replaced by alternative leaf components, abnormal flowers and reduced fertility, was also investigated. Although the root system dry weight, root lengths and nodule numbers of cochleata were similar to those of its wild type, the nodulation phenotype of the mutant was unique. The nodules typically dichotomously branched and multiple callus and root structures emerged from their meristems. These nodule-roots incorporated a peripheral vascular bundle of the nodule into their own central vascular cylinder and both the nodules and roots of the hybrid structures appeared functional.

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Developmental responses of plants to their light environment are of obvious importance to their fitness and survival, and plant photomorphogenesis has been the focus of much study over the past decade. Great advances have been made in our understanding of the photoreceptors involved in photomorphogenic responses, their roles, their biochemical and photochemical nature, and signal transduction processes initiated by the activated photoreceptors. Much of this study has been focussed on the red/far-red phytochrome photoreceptors, for which mutants have now been isolated in a number of model species. The cryptochrome photoreceptors are comparatively less well characterised, with mutants so far only identified in the Arabidopsis CRYJ and CRY2 genes, and the tomato CRY1a gene. The aim of the current research was to extend the characterisation of the structure and function of the cryptochrome gene family to include another major member of the eudicots, the Fabaceae, represented by the garden pea (Pisum sativum L.). The cryptochrome gene family in the garden pea was found to be represented by 3 members: one CRYJ homologue, and two CRY2 homologues. The latter were found to encode full-length predicted cryptochrome products, containing all major functional domains previously identified to be important in cryptochrome function. They appear to have arisen from a gene duplication event that occurred around the time of divergence of the Hologalegina from the Millettioids/Phaseoloids. One member (PsCRY2B) appears to be rapidly diverging from the ancestral sequence, though whether this is a result of random drift or active selection is not known. Sequence alignments with other available angiosperm cryptochrome sequences in the databases (both monocot and dicot) provide support for many of the previously identified conserved motifs potentially responsible for cryptochrome function, and in addition identified a number of motifs in both the N- and C-terminal domains which are conserved in one of the CRYJ or CRY2 subfamilies, but not the other. Many of these motifs contain potential phosphorylation sites introduced or removed from one of the subfamilies. Expression of the three pea cryptochromes was differentially regulated by light. PsCRY1 was up-regulated by blue light (both high- and low fluence-rate), but not white or red light, suggesting some autoregulatory role of the cryptochromes. This was supported by studies of a Pscry1-deficient mutant (see below). PsCRY2A showed a down-regulation of expression under low- but not high fluence-rate blue light, and under white light. The PsCRY2B gene showed a similar pattern of up-regulation to PsCRY1 under blue light, however expression was down regulated under white light as opposed to showing no appreciable change. To further characterise the role of the pea cryptochromes, the M2 of EMS-treated phyA-1 seed was screened for mutants deficient in their blue-light responses. One mutant line was isolated with selective defects in responses to all fluence-rates of blue light. This line was subsequently found to have a G - A substitution at position 749 of the PsCRY1 mRNA coding sequence. This is predicted to mutate a highly conserved glycine residue (Gly250) to glutamic acid. This mutation is in an equivalent residue to that mutated in the Arabidopsis fha-2 mutant, which contains a G - R substitution. The Pscryl-1 mutant displayed similar defects in de-etiolation and flowering responses to previously identified Arabidopsis and tomato cry1 mutants (longer epicotyledonous internodes, smaller leaflets), however they did not show the general cell expansion in all organs seen in the Arabidopsis mutants, suggesting that CRY1 does not mediate a general inhibition of cell expansion in the wild type. The Pscry1-1 single mutant also displayed a much weaker phenotype than its Arabidopsis counterpart, possibly suggesting the cryptochromes have a lesser role in photomorphogenesis of peas. However, a phyAphyBcry1 triple mutant was found to be lethal, failing to show any appreciable de-etiolation even under high-irradiance white light. This suggests that these photoreceptors are collectively necessary for photomorphogenesis in pea, and therefore that PsCRY1 may simply show a higher degree of redundancy with the phytochromes than is seen in Arabidopsis. Screening of the M2 population also yielded a novel late-flowering mutant of pea which shows selective de-etiolation defects to blue, but not red, light. This mutant was named lfp1-1 for its late-flowering photomorphogenic phenotype. This mutant was found to be late flowering under both long- and short days, and to cause a dramatic increase in the extent of aerial branching, along with an increase in internode length, smaller leaflets and darker green foliage. These effects were only seen on a phyA-deficient background in the Torsdag cultivar of pea. On a heterozygous Terese background, the effect of lfp1-1 was also seen in heterozygous PHYA phyA-1 plants. The lfp1 phenotype showed no linkage with the PsCRY2A or PsCRY2B genes, and possibly represents a novel class of signalling intermediate specific to cryptochrome. A single-gene recessive mutant has also been identified from a screen of EMS treated cv. Torsdag seed which shows a hyper-phototropic and hyper-gravitropic phenotype. This mutant displays an increase in the curvature attained under continuous phototropic or gravitropic stimuli due to an extension of the phase of curvature. Mutant plants also display longer epicotyls under all light qualities tested, which was accompanied by a pronounced spiral curving of the internodes. Despite their hyper-phototropic phenotype, mutant plants were found to have an increased down-regulation of PsPK5 expression (a PHOTJ orthologue) on transfer to light. These plants display many similarities to the recently characterised mdr mutants of Arabidopsis, which contain defects in basipetal auxin transport. In summary, examination of the cryptochrome gene family in the garden pea has revealed a novel gene duplication in the CRY2 gene lineage. Alignments of the pea cryptochromes with published sequences has revealed a number of sites potentially involved in cry1 and cry2 regulation, however further work is required to test this. Characterisation of a mutant deficient in the PsCRY1 gene has revealed that cry1 plays a similar role in pea to other species, but does not mediate the general inhibition of cell expansion seen in the Arabidopsis cry1 mutant. In addition, phyA, phyB and cry1 are almost solely responsible for the de-etiolation response of peas. Screening has also identified a number of other mutants with affected photomorphogenic responses that may aid in the investigation of transduction of the light signals.

No description available

Plants develop through at least three distinct phases after germination: a juvenile vegetative phase; an adult vegetative phase; and a reproductive phase. Therefore, there exist two main ontogenetic transitions, the juvenile-adult vegetative transition or vegetative phase change, and the adult vegetative-reproductive phase transition or reproductive phase change. The genetic and physiological control of the transition to flowering has been studied intensively over the past four decades but the other major transition has received much less attention. This study investigates the genetic and physiological regulation of vegetative phase change in the garden pea (Pisum sativum L) using a novel heterochronic mutant, accelerated phase change (apc), which expresses a consistent difference in the rate of vegetative phase change when compared to the wild type plants. Genetic analyses, using morphological and enzyme markers, revealed that the apc locus is on linkage group 131 (between a and aat-p genes) of the garden pea. When the apc and the WT plants were grown under 8 h and 18 h photoperiods to determine the effect of environmental cues on vegetative phase change, the results demonstrated that not only is the timing of vegetative phase change affected by environment but the vegetative and reproductive phase changes are regulated independently. Using isogenic lines differing only in the apc mutation, the nature of changes in the morphology of the shoot apical meristem (SAM) associated with the vegetative phase change was examined. The dimensions of the SAM (width, height and volume) were measured without fixation using an environmental scanning electron microscope. The materials were harvested at a critical time (11 days of age) when the vegetative phase change was being initiated in the SAM of the apc mutant but not the WT. The study found that the dimensions of SAM are larger in the apc mutant than in the WT plant suggesting that the vegetative phase change to the more complex leaf type is controlled genetically via changes in SAM morphology. Reciprocal grafting techniques showed that vegetative phase change was not significantly altered in the apc scion by the WT stocks and vice versa. This indicated that the site of action of the apc mutation is in the shoot system. To determine whether vegetative phase change involved changes in endogenous hormones in the shoot apex, the levels of GA\\(_1\\), GA\\(_{20}\\), IAA and ABA were quantified using GC-MS-SIM. The plant materials were harvested at 11 days after sowing, at the critical time that vegetative phase change was being initiated in the apc SAM, but not in the WT plants. Differential changes in the hormone levels between the apc and WT SAM were sampled by excising only the 2mm long shoot apices. The results showed no significant difference in GA\\(_1\\), GA\\(_{20}\\) and IAA levels between the apc mutant and the WT, which indicates that these hormones are not involved in the vegetative phase change in the garden pea. Although, a significant difference in ABA levels was detected in the SAM of the WT and the apc plants, ABA does not appear to be a crucial hormone in vegetative phase change. Further work showed no significant differences in the rate of vegetative phase change between a prominent ABA-deficient mutant (wi/) and the WT (Wit). The ABA-deficiency of the apc mutant does, however, appear to have a small effect on drought response, with the apc and the WT plants showing differences in transpiration rate and stomatal conductance.

Increasing Zn content of cereals, particularly rice, is an approach for combating global Zn malnutrition. This project aimed to investigate the use of CNPs as a Zn carrier to increase rice Zn content. CDs bound with Zn were used as a foliar spray in the study to determine their effectiveness in delivering Zn to rice plants. The CNPs utilized in the study neither had detrimental effect on the growth nor showed deleterious effect on physiology of the rice plants tested. The possible physiological and molecular mechanism of a Zn efficient rice variety (IR36) and a Zn inefficient variety (IR26) were also studied under CNP. ZnCD application significantly increased shoot and seed Zn content of the IR36 variety, and this response was not seen in the IR26 variety. In contrast, the Fe content of IR 36 seeds increased significantly compared to the bulk Zn application. This validates prior research that found a positive relationship between Zn and Fe uptake in rice. Nonetheless, the responses of the two rice varieties revealed differences in Zn uptake and grain loading demonstrating varying Zn utilization efficiency. Comparative transcriptome and proteome analysis were used to determine the molecular mechanism by which rice responds to CNP-under contrast Zn utilization genetics. RNA-Seq-based transcriptomic analysis found 251 upregulated genes in IR36 in response to ZnCDs that were not upregulated in IR26. These set of activated IR36-specific genes implicated in Zn uptake, grain filling, auxin signalling, and abiotic stress signalling pathways. Our finding clearly demonstrates that the genetics of Zn use efficiency is further amplified by ZnCDs. The comparative proteomics analysis showed ZnCD application to IR36 upregulated 38 proteins, while IR26 upregulated 210 proteins, with just 2 similarities between the two groups. These IR36-specific proteins were heavily implicated in pathways like glucose metabolism, and photosynthesis. Findings of this study could be successfully used in formulation of a CNP based nano-fertilizer which could be used to address the global Zn malnutrition. In addition, greater understanding of the genetic mechanism of Zn utilization efficiency will open up new avenues for breeding and engineering cereals to increase their grain Zn content.

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No description available

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Red clover (Trifolium pratense L.), a key perennial pastoral species used globally, can strengthen pastural mixes to withstand increasingly disruptive weather patterns from climate change. Breeding selections can be refined for this purpose by obtaining an in-depth understanding of key functional traits. A replicated randomized complete block glasshouse pot trial was used to observe trait responses critical to plant performance under control (15% VMC), water deficit (5% VMC) and waterlogged conditions (50% VMC) in seven red clover populations and compared against white clover. Twelve morphological and physiological traits were identified as key contributors to the different plant coping mechanisms displayed. Under water deficit, the levels of all aboveground morphological traits decreased, highlighted by a 41% decrease in total dry matter and 50% decreases in both leaf number and leaf thickness compared to the control treatment. An increase in root to shoot ratio indicated a shift to prioritizing root maintenance by sacrificing shoot growth, a trait attributed to plant water deficit tolerance. Under waterlogging, a reduction in photosynthetic activity among red clover populations reduced several morphological traits including a 30% decrease in root dry mass and total dry matter, and a 34% decrease in leaf number. The importance of root morphology for waterlogging was highlighted with low performance of red clover: there was an 83% decrease in root dry mass compared to white clover which was able to maintain root dry mass and therefore plant performance. This study highlights the importance of germplasm evaluation across water stress extremes to identify traits for future breeding programs

Condensed tannins (CTs, proanthocyanidins) are widespread polymeric flavan-3-ols known for their ability to bind proteins. In poplar (Populus spp.), leaf condensed tannins are induced by both biotic and abiotic stresses, suggesting diverse biological functions. Here we demonstrate the ability of CTs to function as physiological antioxidants, preventing oxidative and cellular damage in response to drought and UV-B irradiation. Chlorophyll fluorescence was used to monitor photosystem II performance, and both hydrogen peroxide and malondialdehyde content was assayed as a measure of oxidative damage. Transgenic MYB-overexpressing poplar (Populus tremula x tremuloides) with high CT content showed reduced photosystem damage and lower hydrogen peroxide and malondialdehyde content after drought and UV-B stress. This antioxidant effect of CT was observed using two different poplar MYB CT regulators, in multiple independent lines and different genetic backgrounds. Additionally, low-CT MYB134-RNAi transgenic poplars showed enhanced susceptibility to drought-induced oxidative stress. UV-B radiation had different impacts than drought on chlorophyll fluorescence, but all high-CT poplar lines displayed reduced sensitivity to both stresses. Our data indicate that CTs are significant defenses against oxidative stress. The broad distribution of CTs in forest systems which are exposed to diverse abiotic stresses suggests that these compounds have wider functional roles than previously realized. This article is protected by copyright. All rights reserved.

Accurate predictions of plant responses to elevated CO2 (eCO2) levels require a better understanding of uptake and allocation of resources that affect growth. While it is well-established that plants can increase C transfer belowground to increase access to nutrients in N-limited environments, there is less studies investigating the role of these adaptations in P-limited systems. In this study, we aimed to characterise plant nutrient use and acquisition strategies under future atmospheric [CO2] scenarios, under P-limited conditions and determine how different levels of water availability regulate these strategies. We exposed four grass species commonly found in the understory of P-limited Australian Eucalyptus woodlands to eCO2 over a period of 14 weeks, under two contrasting water levels. We assessed a suite of root morphological and chemical traits and the rhizosphere activity of extracellular enzymes related to C, N and P cycles, along with changes in plant allocation patterns and use efficiency of these nutrients. Elevated CO2 effects on root functional attributes were species-specific, but clear trends towards increased phosphatase activity were observed across species, leading to a lower C:P ratio. In contrast, water supply affected root morphological attributes, but interactions between CO2 and water levels on functional traits were minor. Greater water availability also stimulated microbial activity in the rhizosphere, but without observable changes in the relative demand for N and P relative to C. Despite changes in rhizosphere processes, eCO2 did not lead to increased plant biomass regardless of water supply, suggesting primary nutrient limitation and a lack of positive rhizosphere feedbacks to plant growth.

Seed dormancy-break via cold stratification is of fundamental importance for plant adaptation to environmental conditions and response to climate change through timing germination, seedling emergence and consequently community dynamics. Although cold stratification requirements for dormancy break vary among species, it is not known if this variation is determined by the environmental conditions experienced by seeds or by differences among species. We determined the soil moisture content and duration of cold stratification required for seed dormancy-break of species from alpine and desert habitats (soil moisture content: 20 and 18 species from alpine and desert habitats, respectively; duration: 16 and 16 species from the alpine and desert, respectively), and examined the correlation between environmental conditions (soil moisture content and duration of cold stratification) required for dormancy-break and seed traits. Seed germination increased and then decreased as soil moisture content or duration of cold stratification increased. The optimal and critical soil moisture content for seed dormancy-break were higher for alpine species than desert species. A positive correlation between optimal soil moisture content and seed shape was found. However, the duration of cold stratification required for dormancy-break was not related to habitat, seed mass or seed shape. Our results suggest that soil moisture content rather than duration of cold stratification resulting from climate change could affect seed germination and consequently seedling emergence and establishment, especially for desert species.

The Brazilian Atlantic Forest has been affected by the deposition of Ni and Zn, among other heavy metals adsorbed on atmospheric particles, which can be incorporated into the soil. If available in the soil, they can be absorbed by plant roots. The study aimed at testing experimentally the hypotheses: 1) Ni and Zn depositions increase their bioavailable fractions in the soil; 2) pioneer tree species absorb Ni and Zn from the soil in higher level and less growth changes than non-pioneer species. The experiment was carried out with six pioneer and non-pioneer species native to the Atlantic Forest, grown for 90 days in: soil with balanced fertilization (control) and in soil enriched with Ni, Zn or Ni + Zn. At the end, the concentrations of Ni and Zn were determined in four soil fractions (F1: soluble; F2: linked to oxides/hydroxides; F3: linked to organic matter: F4: residual metals) and in leaves, stems/branches and roots. Mobility factors in soil, concentration ratios between treatments and respective controls, translocation efficiency and relative growth rate in height, leaf number and total biomass were also calculated. The results showed that Ni and Zn concentrations increased significantly in the bioavailable soil fractions (F1, F2). The absolute content of Ni and Zn in the plants directly reflected the soil level in the available forms. Pioneer tree species absorb Ni and Zn in higher level and show less changes in growth than non-pioneer tree species.

The recent advancement in LED technology led many incubator manufacturers and research labs to switch to these more efficient, yet spectrally restricted, light sources. Potential effects of commercially available broad range “white” light systems on phytoplankton growth, productivity, light absorption spectra, and cellular composition have not yet been characterized but could affect our interpretation of lab-based projections on responses to environmental changes. In this study, we investigated such effects using cultures of Prochlorococcus marinus, Synechococcus sp., and Thalassiosira weissflogii grown under three different commercially available LED lights as well as one fluorescent growth light. Photosynthetically active radiation was equal for each species, while photosynthetically usable radiation differed among the combinations of species and treatments. Growth rate was unaffected across species, yet all species displayed changes in cellular carbon, nitrogen, and chlorophyll a quotas as a direct response to the different light spectra. 14C-based primary productivity was also affected in P. marinus and T. weissflogii. Analysis of pigment ratios and photophysiological data indicated changes in the photoacclimation state between different light environments. The results of this study show that these species undergo changes in underlying cellular metabolism which in turn affect cellular composition while keeping specific growth constant. The data presented here illustrate ecophysiological responses of differently pigmented species when grown under different artificial growth light spectra. These cellular acclimation responses should be considered when designing laboratory-based incubation experiments, especially when comparing responses to specific changes in environmental conditions, or when implementing physiological parameters, derived from laboratory experiments, into numerical models.

Rhizosphere bacterial communities (‘rhizobacteria’) can mediate plant-soil feedbacks that enhance plant drought tolerance, but the composition and ecological characteristics of these populations are poorly understood. We investigated the impact of drought on rhizobacteria communities and the effect of propagating drought-impacted communities on the drought tolerance of naive plants in a two-phase experiment. We tested whether propagating rhizosphere soils from drought-stressed shrub willow (Salix purpurea), or continuously watered controls, affected the performance of a subsequent generation of droughted plants. The impacts of drought on rhizobacteria and plant fitness were evaluated using 16S rRNA gene sequencing and measures of plant growth (root mass and stem length etc.) and stress (abscisic acid, osmolality). Uninoculated reference plants were used to isolate the effects of inoculation. Drought had a significant and lasting impact on the structure of rhizobacterial communities, characterized by increased populations of Actinobacteria (Acidimicrobiia, Thermoleophilia and Micrococcaceae). Foliar osmolality was significantly higher in plants receiving drought-selected communities relative to uninoculated controls, but no significant differences in plant growth were observed. Inoculation with rhizosphere soil from watered controls significantly reduced plant growth. The rhizosphere of watered control plants was dominated by Proteobacteria and Bacteroidetes. Our findings demonstrate that plants are affected by the legacy effects of drought on the rhizosphere microbiome. This drought legacy was propagated and persisted throughout nine weeks of plant growth, independent of prevailing water stress. Drought-impacted rhizospheres had larger populations of desiccation-tolerant (ex. Arthrobacter) and putatively endophytic taxa (ex. Rhizobium) with established plant growth promoting capabilities.

Phytoremediation with augmentation of oxalic acid could improve the removal efficiencies of toxic metals in saline soil. Metal concentrations and species in saline soil, extraction of metals by Sua...

Plant biostimulants such as seaweed extracts, present a sustainable alternative to agrochemicals. Moreover, the accumulation of beach-cast seaweed (wrack), due to climate change and anthropic pressures, is expected to increase in the coming decades. Thus, from a perspective of circular economy, based on the valorisation of an organic residue, this study aimed at achieving an elemental and biochemical characterisation of beach wrack and understanding the effects of an aqueous extract prepared from this residue on the mitigation of metal-induced stress, using barley (Hordeum vulgare L.) as a model. The quantification of wrack’s macro- and micronutrients showed that K, Ca and Na were the most abundant elements, being this composition similar to that of other organic fertilisers. Furthermore, despite the studied wrack having lower values of photosynthetic pigments, amino acids and sugars, higher amounts of phenols and flavonoids (8.35 ± 0.24 and 3.95 ± 1.22 mg g−1 dry matter respectively) were detected when compared to freshly collected seaweeds. This work highlighted that wrack showed potential as a fertiliser—through increasing root biomass (63%) and leaf biometry (up to 45%) in plants treated with 5.0 and 7.5 g L−1 wrack extract alone—also being a possible cost-effective, eco-friendly and sustainable biostimulant to mitigate the phytotoxic effects of Cu, since plants treated with 7.5 g wrack L−1 showed an increase of 34% in leaf length, when compared to seedlings exposed only to Cu.

Mongolian pine transpiration was driven by soil water at the top and vapor pressure deficit at the bottom of sand dunes; this was modulated by interannual variability in water availability. Mongolian pine (Pinus sylvestris var. mongolica) plantations have been suffering frequent diebacks in years of extreme drought due to water deficit in semiarid sandy regions of Northeast China. However, the transpiration dynamics of Mongolian pine trees at different positions of sand dunes and their responses to environmental variables remain unknown. Here, canopy transpiration and conductance of 38-year-old Mongolian pine trees at top (TS) and bottom (BS) of sand dunes were quantified using sap flow method from 2018 to 2019. Canopy transpiration per unit leaf area (EL) was, respectively, 0.45 ± 0.13 and 0.53 ± 0.17 mm d−1 at TS and BS in 2018, with relatively low soil moisture, and it was, respectively, 0.51 ± 0.15 and 0.59 ± 0.19 mm d−1 in 2019, with relatively high soil moisture. Moreover, EL variability explained by climate variables was greater at BS than at TS during 2018, but the trend was reversed during 2019. In addition, canopy conductance at BS was 11.5% higher than that at TS, but magnitude of increase from 2018 to 2019 was higher at TS. Stomatal sensitivity to vapor pressure deficit was higher at BS than at TS in 2018, but comparable in 2019. Consistently, stomatal sensitivity to soil moisture was higher at TS than at BS in 2018, but the trend was reversed in 2019. Taken together, these findings indicate that Mongolian pine trees at TS exhibit lower transpiration, which is primarily driven by soil moisture, than those at BS, presenting greater susceptibility to dieback under extreme drought.

Soil salinization has become a global problem and seriously endangers crop growth and yield improvement. In the present study, soybean (Hefeng 50) seedlings were used as test materials to study the mitigation effect of foliar spraying of different plant growth regulators (PGRs) [50 mg L−1 indole-3-butyric acid potassium salt (IBAK), 50 mg L−1 chitosan oligosaccharide (COS), 2 mg L−1 abscisic acid (ABA), 30 mg L−1 5-aminolevulinic acid (ALA), and 1.2 mg L−1 brassinolide (BR)] on oxidative stress caused by the mixed Saline–Alkali concentration of 110 mmol L−1. The results showed that the application of PGRs promoted the growth of Saline–Alkali stressed plants, where the maximum increase in shoot FW was treated with COS, and in root FW, root length, root surface area, and root volume were obtained with the IBAK treatment. Treatments ABA, ALA, and BR had higher net photosynthetic rates, and the chlorophyll content was considerably increased under COS and BR treatments compared with Saline–Alkali treatment. Moreover, PGRs markedly enhanced the activities of antioxidant enzymes, the concentration of ascorbate (AsA), glutathione (GSH), proline, soluble protein, soluble sugar, sucrose, and starch, and the ratios of AsA/DHA and GSH/GSSG, but reduced the concentration of malondialdehyde (MDA), electrolyte leakage (EL), hydrogen peroxide (H2O2), and superoxide radical (O2·−) in soybean seedlings compared with Saline–Alkali treatment. The principal component analysis revealed that the ranking of PGRs enhancing Saline–Alkali tolerance of soybean seedlings was BR > IBAK > ABA > COS > ALA, and the most effective treatment was BR, which may be assigned to more vigorous antioxidant defense and osmotic adjustment.

Global warming and salinization are inducing adverse effects on crop yield. Drought priming has been proved to improve drought tolerance of plants at later growth stages, however, whether and how drought priming at early growth stage alleviating salinity stress at later growth stage and improving water use efficiency (WUE) of plants remains unknown. Therefore, two wheat cultivars were subjected to drought priming at the 4th and 6th leaf stage and subsequent moderate salinity stress at 100 mmol NaCl applied at the later jointing growth stage. The growth, physiological responses, ABA signaling and WUE were investigated to unravel the regulating mechanisms of drought priming on subsequent salinity stress. The results showed that drought priming imposed at the early growth stage improved the leaf and root water potential while attenuated the ABA concentration in the leaves ([ABA]leaf) for the primed plants, which increased the stomatal conductance (gs) and photosynthesis (Pn). Consequently, the biomass under the salinity stress was significantly increased due to earlier drought priming. Moreover, drought priming improved the specific leaf N content due to the facilitated root growth and morphology, and this could benefit high leaf photosynthetic capacity during the salinity stress period, improving the Pn and water uptake for the primed plants. Drought priming significantly improved plant level WUE (WUEp) due to considerably enhanced dry biomass compared with non-primed plants under subsequent salinity stress. The significantly increased leaf δ13C under drought priming further demonstrated that the improved leaf δ13C and WUEp was mainly ascribed to the improvement of Pn. Drought primed plants significantly improved K+ concentration and maintained the K+/Na+ ratio compared with non-primed plants under subsequent salinity stress, which could mitigate the adverse effects of excess Na+ and minimize salt-induced ionic toxicity by improving salt tolerance for primed plants. Therefore, drought priming at early growth stage could be considered as a promising strategy for salt-prone areas to optimize agricultural sustainability and food security under changing climatic conditions.

Bacteria survived and thrived inside any part of plant without damaging its host are called endophytic bacteria. Many studies have focused on plant–endophytic bacterium interactions and their Plant-growth-promoting (PGP) abilities. Albino tea plants are widely investigated because of their high amino acid concentrations. Previous studies mainly elucidated specific metabolite mechanisms in albino tea plants, while the present study identified the variation in diversity and endophytic bacterial abundance in albino and non-albino tea leaves using culture-dependent and culture-independent methods. With different culture media, we identified a total of 110 isolates, of which 58 endophytic bacteria belonged to three phyla (Proteobacteria, Firmicutes, and Actinobacteria). Moreover, we identified a total of 1856 operational taxonomic units as 513 endophytic bacteria belonging to 27 phyla including Proteobacteria, Firmicutes, and Actinobacteria. In addition, comparing to non-albino tea leaves, endophytic bacteria obtained from albino tea leaves showed higher diversity and abundance. Endophytic bacteria isolated from albino leaves also exhibited higher PGP properties than those from non-albino ones, and their PGP effects on rice and tea cuttings were examined. The results indicated differences in endophytic bacteria between albino and non-albino leaves. Specific endophytic bacteria isolated from albino leaves may have a relationship with the albino phenotype. Our study indicated that PGP bacteria isolated from albino leaves are expected to become a plant growth promoter in the future.

Drought stress exposure adversely affects plant growth and productivity. Various seed priming techniques are experimented to mitigate the adverse effect of drought stress on plant performance. It is a low-cost and sustainable technology that proved to be of immense potential to enhance drought tolerance and increase crop productivity. Drought episodes are followed by recovery through rain or irrigation and help the plants to recuperate from the damages caused by drought stress. The severity of drought-associated damages determines the recovery kinetics of plants. Under the recurrent cycle of drought events, recovery kinetics has immense importance in predicting the stress tolerance potential and survival status of a plant. Many processes like DNA damage repair, de-novo synthesis of nucleic acids and proteins, osmotic adjustment through the accumulation of osmolytes, the potential activity of antioxidant machinery occurring during seed priming play a significant role during recovery from drought stress. Alleviation of the severity of drought stress through the accumulation of osmolytes, the augmented activity of antioxidant machinery, improved photosynthetic performance, and the upregulated expression of stress-responsive genes attributed by seed priming will complement the recovery from drought stress. Although the beneficial effects of seed priming on drought tolerance are well explored, priming influenced recovery mechanism has not been well explored. There is a lacuna in the field of research related to the beneficial effects of seed priming for recovery from drought stress, and that is the focus of this paper.

The circadian clock is a cell autonomously and endogenously regulated biological timekeeper that detects changes in environmental stimuli and generates 24-h rhythms that are synched with day to day and periodic oscillations to govern many biological functions. Plant's circadian clocks enable them to anticipate environmental changes by modifying their physiological and biological traits to improve plant fitness. The internal circadian clock not only aids fitness but also allows the plant to time-gate the response to environmental stimuli. The latest evidence on the circadian clock suggests that the clock regulates/modulates the expression of abiotic stress-responsive pathways to improve tolerance to stresses without hampering plant growth. In turn, stress signaling also influences the activity of several clock components. This review emphasizes the interplay of the biological circadian clock with abiotic stress-responsive pathways (drought, heat, cold, and salt) for plant growth and survival as well as for stress resilience. A better comprehension of these mechanisms could aid in the development of genetic tools to improve breeding procedures and plant stress tolerance, thereby increasing crop yield and quality under changing ecological conditions.

Eclipta prostrata (L.) L. is widely used in traditional medicine for treatment of hepatitis, poisoning from snake bites and viral infections. Pharmacological studies confirmed its antioxidant, anti-inflammatory and anticancer activities. The efficacy of E. prostrata (L.) L. extracts has been correlated to phenylpropanoids such as flavonoids, coumestans and caffeoylquinic acid derivatives. In this work, the production of wedelolactone, demethylwedelolactone and 3,5-di-O-caffeoylquinic acid (3,5-diCQA) in hairy root cultures of E. prostrata (L.) L. C19 clone was increased after addition of eliciting agents jasmonic acid (JA) or methyl jasmonate (MeJA) at multiple concentrations. Cultures elicited with 100 μM of JA saw a 5.2 fold increase in wedelolactone (from 0.72 to 3.72 mg/g d.w.), a 1.6 fold increase in demethylwedelolactone (from 5.54 to 9.04 mg/g d.w.) and a 2.47 fold increase in 3,5-diCQA (from 18.08 to 44.71 mg/g d.w.). Obtained data validate the potential of E. prostrata (L.) L. hairy root cultures as a production system of wedelolactone, demethylwedelolactone and especially 3,5-diCQA, which has recently been reported to possess activity against coronavirus disease (Covid-19) by in silico computational studies. The goal of this work was to evaluate the effect of jasmonic acid (JA) or methyl jasmonate (MeJA) on wedelolactone, demethylwedelolactone and 3,5-di-O-caffeoylquinic acid (anti-Covid-19 drug candidate) production from hairy root cultures of Eclipta prostrata (L.) L. C19 clone.

Rice seedlings were treated with different concentrations of Pb solutions or /and CO2 (Pb 0 μM + CO2 400 ± 20 μmol/mol, AC; Pb 0 μM + 800 ± 20 µmol/mol, EC; Pb 50 μM + CO2 400 ± 20 μmol/mol, L; Pb 150 μM + CO2 400 ± 20 μmol/mol, H; Pb 50 μM + CO2 400 ± 20 μmol/mol, EC + L; Pb 150 μM + CO2 800 ± 20 μmol/mol, EC + H;), so as to study the effects of Pb stress and/or elevated CO2 on growth, photosynthesis, and endogenous hormones. We measured the biomass, photosynthetic gas exchange parameters, fluorescence parameters and their curves (O-J-I-P, Variable fluorescence) and the contents and ratio of endogenous hormones in rice seedlings. The results show that: (1) Both L and H had negative effects on the growth of rice seedlings. However, H treatment had a significant negative effect on PSII of rice seedlings, but L treatment had no significant effect. In addition, JA (jasmonic acid) and ABA (abscisic acid) were significantly associated with the decrease of GS in Rice under Pb stress. (2) Under EC treatment, the secretion of growth hormones increased significantly. More importantly, the content of JA increased significantly while GS decreased, but ABA did not, which may mean that JA is more sensitive to stomatal regulation under EC. (3) Compared with L and H, EC + L and EC + H manifested in the enhancement of photosynthetic performance and adjustment of hormone ratio. Compound treatment significantly increased the ratio of “promoting-hormone to ABA” compare with L and H treatment. The biomass accumulation of rice seedlings increased significantly after being affected by changes in hormone ratios and enhanced photosynthesis. Therefore, the high concentration CO2 reduces the harm of Pb to a certain extent. However, this relief is also limited. Compared with H, EC + H has no alleviating effect on rice seedling most growth and photosynthetic parameters.

The secondary salinization of soil in facility agriculture is becoming increasingly serious. Cucumber is a moderately salt-sensitive crop, but because of the weak root system and poor resistance to salt stress in cucumber seedlings, it is sensitive to the accumulation of salt in facility soils. Hydrogen, a selective antioxidant and signal molecule, is nontoxic and harmless, and can repair damage in plants under stress. Therefore, the aim of the present paper was to understand the specific mechanism by which hydrogen-rich water (HRW) alleviated salt stress in cucumber seedlings (Cucumis sativus L.). Our results showed that the addition of 50% saturation HRW significantly promoted seedling growth, development and photosynthetic efficiency. Pretreatment with HRW significantly alleviated salt stress symptoms, including the inhibition of fresh and dry weight, root length, lateral roots, and the root/shoot ratio of cucumber seedlings. Pretreatment with HRW increased the chlorophyll content, chlorophyll a/b ratio, and photochemical reaction efficiency, and reduced energy dissipation. These responses to HRW pretreatment were consistent with significant decreases in the superoxide anion, hydrogen peroxide, and malondialdehyde contents and the degree of lipid peroxidation, and increases in the activities of SOD, POD, CAT, APX and GR, and the contents of ASA and GSH in cucumber seedlings under salt stress. In addition, HRW pretreatment under salt stress inhibited the expression of the protein kinase ROP1, which promoted the production of reactive oxygen, but upregulated the protein kinase LecRLK. The transcription factor TGA5, which was involved in osmotic stress, ion stress and ROS clearance, and the expression of NHX1 and SOS2, which were parts of the SOS signaling pathway. HRW enhanced the expression of genes that encoded antioxidant enzymes, including SOD, CAT and POD, and the expressions of GR and APX2, which were key genes in the ASA-GSH cycle under salt stress. Taken together, these results suggested that HRW enhanced the active oxygen scavenging ability in cucumber seedlings, promoted the redox balance in cells, and reduced the degree of oxidative damage in plants under salt stress by reducing the content of active oxygen. Therefore, the application of HRW might be a promising strategy for improving salt stress tolerance in cucumber seedlings.

Garlic chives (Allium tuberosum Rottler ex Sprengel) are an underutilized and neglected food crop of the Allium genus. For the future genetic development of alliums, phenotypic characterization and insights of breeding behaviour could be the aid to breed the new garlic chives varieties. Field Emission Scanning Electron Microscopy (FESEM) was used to reveal the morphological features of male gametophytes. The anther was reticulate, conspicuous, folded surface with scaly plates, and pollen was found to be sub-ovoid morphologies with long regulate and striated sexine. Spectra from FESEM-based Energy Dispersive X-ray Spectroscopy (EDS) revealed the elemental composition and distribution. The micrograph of an anther sample revealed the presence of O, C, K, P, N, Fe, Mn, Zn, and Mg minerals, as well as C, O, N, P, K, Fe, Ca, Mn, Mg, Zn, Cu, Na, and Cl minerals in the pollen grain. These insights of male gametophytes traits and characteristics, relative mineral composition and breeding behaviour could aid in the better understanding, characterization, identification and genetic improvement of A. tuberosum.

Among wild relatives of cultivated almond and plum, a desert almond species, but not a montane plum species, showed higher drought resistance than the common rootstocks routinely used in orchards. Water shortage is a severe environmental factor causing growth disruption and yield-\loss in many agricultural plant species. As fruit trees are likely to suffer from the effects of severe drought in the future, wild relatives of cultivated crops can provide plant breeders a unique material to improve the drought resistance of modern crop varieties. We conducted a drought and rewatering greenhouse experiment along 51 days with young trees of almond (the desert wild species Prunus ramonensis vs. the commonly used rootstock hybrid Prunus dulcis × Prunus persica) and plum (the montane wild species Prunus ursina vs. the rootstock Prunus cerasifera × Prunus persica). To decipher the drought resistance mechanisms in these trees we monitored physiological responses. Expression dynamics of cellular water channels from the plasma intrinsic protein (PIP) aquaporin family were measured in the almond species. Our results indicate a higher drought resistance in wild almond compared to the rootstock, but not in the wild plum species. Under drought, P. ramonensis had ~ ninefold higher photosynthesis activity, ~ 50-fold higher water-use efficiency and lower vulnerability to embolism than the rootstock. In the almond species, PIP downregulation was linked with maintenance of hydraulic conductivity, and vice versa for upregulation. This study implies that there is a link between drought resistance in wild tree species and their native habitat conditions, with an advantage for the desert, but not the montane, species. Finally, our study highlights the need to protect and conserve wild relatives of fruit tree species, partly as potential plant materials to be used by breeders to improve the resilience of orchard tree species to drought.

Key message We identified two poplar clones of the same species as highly comparable, yet clones of two further species of the same genus to be distinctly different regarding multiple morphological and ecophysiological traits. Abstract Leaf morphology, wax composition, and residual (cuticular) transpiration of four poplar clones (two clones of the hybrid species P. × canescens, P. trichocarpa, and P. euphratica) were monitored from the beginning to end of the growing season 2020. A pronounced epicuticular wax coverage was found only with P. euphratica. As the most prominent substance classes of cuticular wax primary alcohols, alkanes and esters were identified with P. × canescens and P. trichocarpa, whereas esters and alkanes were completely lacking in P. euphratica. Wax amounts were slightly decreasing during the season and significantly lower wax amounts were found for newly formed leaves in summer compared to leaves of the same age formed in spring. Residual (cuticular) transpiration was about five to tenfold lower for P. × canescens compared with the two other poplar species. Interestingly, with three of the four investigated species, newly formed leaves in summer had lower wax coverages and lower rates of residual (cuticular) transpiration compared to leaves of exactly the same age formed in spring. Our findings were especially surprising with P. euphratica, representing the only one of the four investigated poplar species naturally growing in very dry and hot climates in Central Asia. Instead of developing very low rates of residual (cuticular) transpiration, it seems to be of major advantage for P. euphratica to develop a pronounced epicuticular wax bloom efficiently reflecting light.