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Over the last two decades, significant advances have been made using genetic engineering technology to modify genes from various exotic origins and introduce them into plants to induce favorable traits. RNA interference (RNAi) was discovered earlier as a natural process for controlling the expression of genes across all higher species. It aims to enhance precision and accuracy in pest/pathogen resistance, quality improvement, and manipulating the architecture of plants. However, it existed as a widely used technique recently. RNAi technologies could well be used to down-regulate any genes' expression without disrupting the expression of other genes. The use of RNA interference to silence genes in various organisms has become the preferred method for studying gene functions. The establishment of new approaches and applications for enhancing desirable characters is essential in crops by gene suppression and the refinement of knowledge of endogenous RNAi mechanisms in plants. RNAi technology in recent years has become an important and choicest method for controlling insects, pests, pathogens, and abiotic stresses like drought, salinity, and temperature. Although there are certain drawbacks in efficiency of this technology such as gene candidate selection, stability of trigger molecule, choice of target species and crops. Nevertheless, from past decade several target genes has been identified in numerous crops for their improvement towards biotic and abiotic stresses. The current review is aimed to emphasize the research done on crops under biotic and abiotic stress using RNAi technology. The review also highlights the gene regulatory pathways/gene silencing, RNA interference, RNAi knockdown, RNAi induced biotic and abiotic resistance and advancements in the understanding of RNAi technology and the functionality of various components of the RNAi machinery in crops for their improvement.

Drought is increasing prevalently, mostly due to global warming, and harmful effects associated with drought stress include a reduction in the developmental phases of the plant life cycle. Drought stress affects vital metabolic processes in plants such as transpiration, photosynthesis and respiration. The other physiological and cellular processes like protein denaturation and aggregation are also affected by drought. Drought stress severely affects the floral industry by reducing the yield of flowers and among them is chrysanthemum (Dendranthema grandiflorum). In this study, we determined the critical signaling pathways, tolerance mechanism and homeostatic maintenance to drought stress in chrysanthemum. We compared the proteome of chrysanthemum leaves under drought stress. Among 250 proteins on 2DE gels, 30 protein spots were differentially expressed. These proteins were involved in major signaling pathways including, stress response, flower development and other secondary metabolism like physiological transport, circadian rhythm, gene regulation, DNA synthesis and protein ubiquitination. A reduction in a biomass, flower development, photosynthesis, transpiration, stomatal conductance, PSII yield and stomatal index was also observed in our results. Moreover, the stress markers and leaf water potential were also analyzed to depict the level of stress tolerance in chrysanthemum. Our data suggested that chrysanthemum plants developed reactive oxygen species and revealed signaling pathways to cope with drought stress. These results, thus, provide crucial information about how chrysanthemum plants respond to drought stress to maintain homeostasis.

Plants require an endogenous regulatory network and mechanism to cope with diurnal environmental changes and compensate for their sessile nature. Plants use the circadian clock to anticipate diurnal changes. Circadian rhythm predicts a 24-h cycle with 16 h of light and 8 h of darkness in response to abiotic and biotic factors as well as the appropriate temperature. For a plant’s fitness, proper growth, and development, these rhythms synchronize the diurnal photoperiodic changes. Input pathway, central oscillator, and output pathway are the three components that make up the endogenous clock. There are also transcriptional and translational feedback loops (TTFLs) in the clock, which are dependent on the results of gene expression. Several physiological processes, such as stress acclimatization, hormone signaling, morphogenesis, carbon metabolism, and defense response, are currently being investigated for their interactions with the circadian clock using phenotypic, genomic, and metabolic studies. This review examines the role of circadian rhythms in the regulation of plant metabolic pathways, such as photosynthesis and carbon metabolism, as well as developmental and degenerative processes, such as flowering and senescence. Furthermore, we summarized signaling pathways related to circadian rhythms, such as defense response and gene regulatory pathways.

Understanding the fruit ripening mechanism is critical for fruit quality improvement. Although postharvest ethylene application is known to enhance the onset of fruit ripening, the exact mechanisms remain unclear. In this study, a gel-based proteomic analysis was performed to investigate the changes in protein profiles during the ripening of exogenous-ethylene-treated kiwifruit (Actinidia deliciosa) cultivars ‘Hayward’ and ‘Garmrok’. Based on comparative two-dimensional gel electrophoresis, most of the proteins were aggregated in exogenous-ethylene-treated kiwifruit compared to the untreated kiwifruit. Consequently, 90 and 106 proteins were differentially expressed in ‘Hayward’ and ‘Garmrok’ kiwifruit, respectively. Among the successfully identified proteins by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry, the 50% in ‘Hayward’ kiwifruit and 60% in ‘Garmrok’ kiwifruit were associated with ripening. Also, 18% and 10% of proteins were associated with defense response in ‘Hayward’ and ‘Garmrok’ kiwifruit, respectively. The other major proteins were related to protein biosynthesis and photosynthesis/Calvin cycle during kiwifruit ripening. We used bioinformatics analysis to determine the interactions between identified proteins, and this proteomic approach provided insights into biological pathways and molecular functions in postharvest ripening of exogenous-ethylene-treated kiwifruit.

Drought stress is one of the most adverse abiotic stresses that hinder plants' growth and productivity, threatening sustainable crop production. It impairs normal growth, disturbs water relations and reduces water-use efficiency in plants. However, plants have evolved many physiological and biochemical responses at the cellular and organism levels, in order to cope with drought stress. Photosynthesis, which is considered one of the most crucial biological processes for survival of plants, is greatly affected by drought stress. A gradual decrease in CO2 assimilation rates, reduced leaf size, stem extension and root proliferation under drought stress, disturbs plant water relations, reducing water-use efficiency, disrupts photosynthetic pigments and reduces the gas exchange affecting the plants adversely. In such conditions, the chloroplast, organelle responsible for photosynthesis, is found to counteract the ill effects of drought stress by its critical involvement as a sensor of changes occurring in the environment, as the first process that drought stress affects is photosynthesis. Beside photosynthesis, chloroplasts carry out primary metabolic functions such as the biosynthesis of starch, amino acids, lipids, and tetrapyroles, and play a central role in the assimilation of nitrogen and sulfur. Because the chloroplasts are central organelles where the photosynthetic reactions take place, modifications in their physiology and protein pools are expected in response to the drought stress-induced variations in leaf gas exchanges and the accumulation of ROS. Higher expression levels of various transcription factors and other proteins including heat shock-related protein, LEA proteins seem to be regulating the heat tolerance mechanisms. However, several aspects of plastid alterations, following a water deficit environment are still poorly characterized. Since plants adapt to various stress tolerance mechanisms to respond to drought stress, understanding mechanisms of drought stress tolerance in plants will lead toward the development of drought tolerance in crop plants. This review throws light on major droughts stress-induced molecular/physiological mechanisms in response to severe and prolonged drought stress and addresses the molecular response of chloroplasts in common vegetable crops. It further highlights research gaps, identifying unexplored domains and suggesting recommendations for future investigations.

A reduction in crop productivity in cultivable land and challenging environmental factors have directed advancement in indoor cultivation systems, such that the yield parameters are higher in outdoor cultivation systems. In wake of this situation, light emitting diode (LED) lighting has proved to be promising in the field of agricultural lighting. Properties such as energy efficiency, long lifetime, photon flux efficacy and flexibility in application make LEDs better suited for future agricultural lighting systems over traditional lighting systems. Different LED spectrums have varied effects on the morphogenesis and photosynthetic responses in plants. LEDs have a profound effect on plant growth and development and also control key physiological processes such as phototropism, the immigration of chloroplasts, day/night period control and the opening/closing of stomata. Moreover, the synthesis of bioactive compounds and antioxidants on exposure to LED spectrum also provides information on the possible regulation of antioxidative defense genes to protect the cells from oxidative damage. Similarly, LEDs are also seen to escalate the nutrient metabolism in plants and flower initiation, thus improving the quality of the crops as well. However, the complete management of the irradiance and wavelength is the key to maximize the economic efficacy of crop production, quality, and the nutrition potential of plants grown in controlled environments. This review aims to summarize the various advancements made in the area of LED technology in agriculture, focusing on key processes such as morphological changes, photosynthetic activity, nutrient metabolism, antioxidant capacity and flowering in plants. Emphasis is also made on the variation in activities of different LED spectra between different plant species. In addition, research gaps and future perspectives are also discussed of this emerging multidisciplinary field of research and its development.

Exogenous applications of silicon (Si) can initiate cellular defence pathways to enhance plant resistance to abiotic and biotic stresses. Plant Si accumulation is regulated by several transporters of silicic acid (e.g. Lsi1, Lsi2, and Lsi6), but the precise mechanisms involved in overall Si transport and its beneficial effects remains unclear. In stressed plants, the accumulation of Si leads to a defence mechanism involving the formation of amorphous or hydrated silicic acid caused by their polymerization and interaction with other organic substances. Silicon also regulates plant ionic homeostasis, which involves the nutrient acquisition, availability, and replenishment in the soil through biogeochemical cycles. Furthermore, Si is implicated in modulating ethylene-dependent and jasmonate pathways, as well as other phytohormones, particularly under stress conditions. Crosstalk between Si and phytohormones could lead to improvements in Si-mediated crop growth, especially when plants are exposed to stress. The integration of Si with reactive oxygen species (ROS) metabolism appears to be a part of the signaling cascade that regulates plant phytohormone homeostasis, as well as morphological, biochemical, and molecular responses. This review aims to provide an update on Si interplays with ROS, phytohormones, and other signaling molecules that regulate plant development under stress conditions., Dr. Durgesh Kumar Tripathi is thankful to the Amity University Uttar Pradesh, Noida for providing necessary research facilities. Dr. Durgesh Kumar Tripathi and Prof. Shivesh Sharma are also thankful to CSIR New Delhi for providing research grants (PID-38(1460)/18/EMR-II). Research in Francisco J. Corpas laboratory is supported by a European Regional Development Fund cofinanced grant from the Ministry of Economy and Competitiveness (PID2019–103924GB-I00), the Plan Andaluz de Investigación, Desarrollo e Innovación (PAIDI 2020) (P18-FR-1359) and Junta de Andalucía (group BIO192), Spain. This work was also supported by the Slovak Research and Development Agency, the contract No. APVV-17–0164, Slovak Grant Agency VEGA 2/0018/17 and by the Serbian Ministry for Education, Science and Technological Development, the contract No. 451–03-68/2020–14/200053.

Silicon is a beneficial element to improve the biological process, growth, development, and crop productivity. The review mainly focuses on the advantage of crops supplemented with silicon, how Si alleviate abiotic stress as well as regulate the genes and proteins involved in metabolic and biological functions in plants. Abiotic stress causes damage to the proteins, nucleic acids, affect transpiration rate, stomatal conductance, alter the nutrient balance, and cell desiccation which could reduce the growth and development of the plants. To overcome from this problem researchers, focus on beneficial element like silicon to protect the plants against various abiotic stresses. The previous review reports are based on the application of silicon on salinity and drought stress, plant defense mechanism, the elevation of plant metabolism, enhancement of the biochemical and physiological properties, regulation of secondary metabolites and plant hormone. Here, we discuss about the silicon uptake and accumulation in plants, and silicon regulates the reactive oxygen species under abiotic stress, further we mainly focus on the genes and proteins which play a vital role in plants with silicon supplementation. The study can help the researchers to focus further on plants to improve the advancement in them under abiotic stress.

To manage nutrient deficiencies, plants develop both morphological and physiological responses. The studies on the regulation of these responses are limited; however, certain hormones and signaling components have been largely implicated. Several studies depicted ethylene as a regulator of the response of some nutrient deficiencies like iron, phosphorous and potassium. The present study focused on the response of sulfur in the presence and absence of ethylene. The experiments were performed in hydroponic nutrient media, using oilseed rape grown with or without sulfur deficiency and ethylene treatments for 10 days. The ACC oxidase and ACC synthase were observed significantly reduced in sulfur-deficient plants treated with ethylene compared to control. The biomass and photosynthetic parameters, including the expression of multicomplex thylakoidal proteins showed a significant increase in sulfur deficient plants supplemented with ethylene. The enzymes related to sulfur regulation such as sulfate adenyltransferase, glutamine synthetase and O-acetylserine (thiol)lyase also showed similar results as shown by the morphological data. The relative expression of the sulfur transporter genes BnSultr1, 1, BnSultr1, 2, BnSultr4,1, BnSultr 4,2, ATP sulfurylase and OASTL increased in sulfur-deficient plants, whereas their expression decreased when ethylene was given to the plants. Fe and S nutritional correlations are already known; therefore, Fe-transporters like IRT1 and FRO1 were also evaluated, and similar results as for the sulfur transporter genes were observed. The overall results indicated that ethylene regulates sulfur acquisition by regulating the expression of sulfur transporter genes in oilseed rape (Brassica napus).

Reflective plastic film mulches are used in orchards to improve fruit coloration and physical properties of plant. The present study was aimed to investigate the effect of reflective plastic film mulching on photosynthetically active radiation (PAR), number of flower buds, average berry yield, total phenol content and anthocyanin content of southern highbush blueberry cv. ‘O’ Neal’. The mulching treatment has showed a considerable effect on PAR and PAR was consistently increased at every 20 cm of bush height from May to September. Interestingly, blueberry yield significantly increased in abundance at the time of harvesting in mulched bushes. Furthermore, total phenol and anthocyanin contents were significantly higher in fruits harvested from mulched bushes compared to control. Besides, higher numbers of flower buds were observed in mulched blueberry bushes than the non-mulched bushes. Consequently, the reflective plastic film mulching can be recommended to implement in blueberry orchards for enhance the productivity of blueberry plants.

We examined the effect of source, concentration, and application method of silicon (Si) on the growth, development, and photosynthetic capacity of Fragaria × ananassa ‘Maehyang’ and ‘Seolhyang’. We applied 0, 35, or 70 mg L−1 Si in a potassium silicate (K2SiO3), sodium silicate (Na2SiO3), or calcium silicate (CaSiO3) solution to plants via subirrigational supply or foliar application. Plant height of ‘Maehyang’ was highest with the 70 mg L−1 Si Na2SiO3 foliar application, but it was not significantly different among treatments in ‘Seolhyang’. Crown size was not significantly affected by source, concentration, or application method in both cultivars. Elemental concentrations in the shoot and root of ‘Maehyang’ were the highest in the 35 mg L−1 Si Na2SiO3 treatment for both application methods. Elemental concentrations in the shoot and root of ‘Seolhyang’ were the highest in the 70 mg L−1 Si K2SiO3 foliar application. Photosynthetic proteins abundantly increased in both cultivars with the 35 or 70 mg L−1 Si K2SiO3 treatment, for both application methods. Moreover, two important photosynthetic proteins, viz. PsaA and PsbA, were expressed and their expressions were higher with the 35 or 70 mg L−1 Si K2SiO3 treatment, for both application methods. These results suggested that 35 or 70 mg L−1 Si, supplied in the form of K2SiO3, promoted photosynthetic protein expressions the greatest, regardless of the application method, in both ‘Maehyang’ and ‘Seolhyang’.

Availability of silicon (Si) to the plant as a silicic acid could be a limiting factor for crop productivity. Although the effect of Si has been shown to vary by plant species, Si has been shown to improve photosynthesis, and to remediate nutrient imbalances and abiotic stresses in plants. Plants of two Korean strawberry cultivars ‘Seolhyang’ and ‘Maehyang’ at a propagation stage was grown for 58 days with a complete nutrient solution (EC of 0.8 dS m−1) and also with supplementation of either 0, 35, or 70 mg L−1 Si from either potassium silicate (K2SiO3), sodium silicate (Na2SiO3), or calcium silicate (CaSiO3). The Si in solution was supplied to the roots through subirrigational nutrient solution or to the leaves by daily foliar applications. The growth and development of the plants were assessed after this period. Then the plants were subjected to one of different salt stress conditions (EC of either 0.0, 0.8, 1.6, or 2.4 dS m−1) for 14 days. The high EC (2.4 dS m−1) resulted in oxidative stress in the form of H2O2 and O 2 −1 in the leaves of the Si-non-treated plants as compared to Si-treated plants, and no or less stress was observed in the 0.0, and 0.8 or 1.6 dS m−1, respectively. However, Si, especially supplied from K2SiO3, relieved the stress level. Interestingly, the isozyme activities of three important antioxidant enzymes, superoxide dismutase, catalase and guaiacol peroxidase, were abundantly increased in the Si-treated plants, particularly with K2SiO3, even under the high EC (2.4 dS m−1) treatment and decreased in the Si-non-treated plants. The observed responses to Si supply in high salt-stressed plants indicate that Si, particularly supplied from K2SiO3, has a significant role in limiting the negative effects of salt stress by maintaining antioxidative enzymes during the vegetative propagation.

As climate changes increase, drought stress is becoming a problem for all major horticultural crops; among them is okra (Abelmoschus esculentus). Despite its superior resilience to heat stress and high nutritional content, it is still underutilized in contrast to other vegetable crops. Moreover, the drought-resistant and drought-sensitive genotypes of okra are also not well known and require further exploration to improve their productivity. To investigate this in more detail, we performed comparative physiological and large-scale chloroplast proteomics on drought-stressed genotypes of okra. We evaluated four major genotypes of okra, viz., NS7774, NS7772, Green Gold, and OH3312 for drought resilient rootstock. The physiological modulations demonstrated a significant change by 50–76% in biomass, net-photosynthetic machinery, water transport, and absorption both in early and late stages of drought stress compared to well-watered crops in all genotypes. Maximum oxidative damage due to drought stress was observed for the genotypes NS7772, Green Gold and OH3312 as depicted by H2O2 and O2− determination. Greater oxidative stress was correlated to lesser antioxidant activity and expression of antioxidant enzymes, such as catalase and ascorbate peroxidase under stress in okra genotypes. The overall photosynthetic pigments, such as total chlorophyll, and total carotenoid content, were also decreased, and stomatal guard cells were disrupted and appeared closed compared to the control for the above three mentioned genotypes, except NS7774. A subsequent tissue-specific proteome analysis of chloroplasts and thylakoids analyzed by BN-PAGE (blue native polyacrylamide gel electrophoresis) revealed either over or under expression of specific proteins, such as ATPase, PSI, PSII core dimer, PSII monomer and ATP synthase. The expression of multiprotein complex proteins, including PSII-core dimer and PSII-core monomer, was slightly higher for the genotype NS7774 when compared to three other genotypes for both 5 and 10 days of drought stress. Further identification of specific proteins obtained in second dimension BN-PAGE provided descriptive detail of seven proteins involved in drought resistance across all genotypes. The identified proteins are majorly involved in photosynthesis under drought stress, suggesting NS7774 as a drought tolerant genotype. Further, the proteomic results were confirmed using Immunoblot by selecting specific protein such as PsaA. Overall, from our physiological modulations and chloroplast proteomics in all genotypes, we summarized NS7774 as a resilient rootstock and the other three genotypes (NS7772, OH3312, and Green Gold) as sensitive ones.

The present study was to determine the factors that can reduce hyperhydricity in in vitro-propagated carnation genotypes. The carnation genotypes (Green Beauty, Purple Beauty, and Inca Magic) were grown in vitro under normal and hyperhydric conditions in white fluorescent light (FL) in which half of the hyperhydric plants were grown in red and blue LEDs (light emitting diodes). It was observed that hyperhydricity leads to oxidative stress in terms of TBARS (thiobarbituric acid reactive substances) content, whereas stress was alleviated by R (red) and B (blue) LEDs. The multiprotein complex proteins such as ATPase (RCI + LHC1) PSII-core dimer, PSII-monomer/ATPs synthase, and PSII-monomer/cyt b6f had decreased levels in hyperhydric conditions grown in white FL; however, the expression level of these photosynthetic proteins was retained in hyperhydric plants grown in R and B LEDs. Moreover, the immunoblots of two photosynthetic proteins (PsaA and PsbA) and stress-responsive proteins such as superoxide dismutase, ascorbate peroxidase, and catalase showed recovery of hyperhydricity in carnation genotypes grown in R and B LEDs. Our present study signifies that red (R) and blue light (B) LEDs reduced the hyperhydricity to control levels by maintaining the composition of thylakoid proteins and antioxidative defense mechanisms in carnation genotypes.

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in the geranium Pelargonium × hortorum L.H. Bailey ‘Ringo 2000 Violet’ (day neutral plant, DNP). Plants were grown in an environment-controlled chamber under a constant light intensity of 180 μmol·m-2·s-1 PPF. The light was supplied by white (W) light emitting diodes (LEDs) to create long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD with a 4 h night interruption (NI) conditions. The NI was provided by green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at a significantly reduced intensity of 10 μmol·m-2 ·s-1 PPF (only 5.5% of the intensity of the main light source). Plant height was greatest under NI-Fr. The percent flowering was not affected by light quality during NI, and all plants flowered under all treatments. Among NI treatments, days to visible flower buds (DVB) increased under NI-Fr. All photoreceptor genes except phyB and FTL were highly expressed under normal LD conditions. Under the NI treatment with different qualities of light, these photoreceptor genes were expressed at even higher levels, except under NI-B, as compared to SD. These results suggest that morphogenesis, flowering, and the expression of transcription factor genes are affected by light quality during NI. Light quality during NI in the DNP geranium has more pronounced effects on morphogenesis than on flowering.

Salinity stress hinders the growth potential and productivity of crop plants by influencing photosynthesis, disturbing the osmotic and ionic concentrations, producing excessive oxidants and radicals, regulating endogenous phytohormonal functions, counteracting essential metabolic pathways, and manipulating the patterns of gene expression. In response, plants adopt counter mechanistic cascades of physio-biochemical and molecular signaling to overcome salinity stress; however, continued exposure can overwhelm the defense system, resulting in cell death and the collapse of essential apparatuses. Improving plant vigor and defense responses can thus increase plant stress tolerance and productivity. Alternatively, the quasi-essential element silicon (Si) – the second-most abundant element in the Earth’s crust – is utilized by plants and applied exogenously to combat salinity stress and improve plant growth by enhancing physiological, metabolomic, and molecular responses. In the present review, we elucidate the potential role of Si in ameliorating salinity stress in crops and the possible mechanisms underlying Si-associated stress tolerance in plants. This review also underlines the need for future research to evaluate the role of Si in salinity stress in plants and the identification of gaps in the understanding of this process as a whole at a broader field level.

Silicon (Si) is the second most abundant element in the soil and is known to help in crop productivity. Si improves photosynthesis as well as remediates nutrient imbalances and abiotic stresses in plants. The impact and the importance of different sources, concentration, and supply of Si in improving the propagation of horticultural crops are limited. Thus, the present study focused on the supply, concentration, and source of Si on two important Korean strawberry cultivars ‘Sulhyang’ and ‘Maehyang’ under temperature stress. The high temperature (41 °C) resulted in oxidative stress in the form of H2O2 and O2 1− localizations in the -Si- and Si-treated plants as compared to 25 or 33 °C in both cultivars. However, Si, especially that from K2SiO3 source, had the ability to relieve the stress level. The immunoblots of two important photosynthetic proteins PsaA and PsbA showed decreased expression levels in the -Si plants under 41 °C temperature stress, whereas the expression levels were retained in the Si-supplied plants, particularly with K2SiO3 as the Si source. In both 25 and 33 °C, no changes in expressions of PsaA and PsbA were observed. Interestingly, the expression of three important stress-responsive proteins, superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), were abundantly increased in the Si-treated plants under high-temperature stress (41 °C) and decreased in the –Si-treated plants except in those grown in 25 or 33 °C. The observed responses to silicon supply in high temperature stressed-plants indicate that Si, particularly in the form of K2SiO3, has a significant role in limiting the negative effects of high temperature stress by maintaining the photosynthetic proteins and stress-responsive proteins of the ascorbate glutathione defense mechanism. Moreover, these results also depict that Si application is a good way to maintain the health of plants at the propagation stage even under high temperatures of greenhouses.

This study investigated the effect of different relative humidity (RH) regimes on graft healing of grafted seedlings of watermelon (Citrullus vulgaris Schrad.). Two watermelon cultivars (‘Speed’ and ‘Sambok Honey’) were grafted onto the ‘RS-Dongjanggun’ bottle gourd rootstock (Lagenaria siceraria Stanld.) and the grafted seedlings were maintained under one of three relative humidity regimes, 95-96% [1.1-0.8 (day) or 0.8-0.6 (night) g·m -3 vapor pressure deficit (VPD)], 97-98% [ 0.7-0.4 (day) or 0.5-0.3 (night) g·m -3 (VPD)], or 99-100% [0.3-0.0 (day) or 0.2-0.0 (night) g·m -3 (VPD)] according to the Mollier diagram based on the air temperature of 25℃ day/18℃ night with 16 h photoperiod per day. Among the RH treatments, 97-98% significantly increased plant height and fresh weight of the rootstock and scion of the ‘Speed’ and it also enhanced the graft union connection of both cultivars after two days of grafting. However, plant height and thickness of the scion of ‘Sambok Honey’ was increased by the 99-100% RH treatment. Furthermore, both cultivars grown in the 95-96 and 97-98% RH treatments consisted of lower levels of endogenous H₂O₂ and less activities of antioxidant enzymes which illustrated the occurrence of less oxidative stress. Hence, the results of this study identified the optimal RH level for the graft healing of watermelon seedlings.

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in Petunia hybrida Hort. ‘Easy Wave Pink’ (a qualitative long-day plant, LDP). Plants were grown in a closed-type plant factory under a constant light intensity of 180 μmol·m-2·s-1 PPF provided by white (W) light emitting diodes (LEDs) under long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD conditions with a 4 h NI using green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at an intensity of 10 μmol·m-2·s-1 PPF. Shoot length was greatest under NI-Fr. Flowering was observed under LD, NI-G, NI-Fr, and NI-W. The expression of photoreceptor genes was induced by NI. Specifically, phyA, phyB, and cry1 were more highly expressed under NI-G, NI-B, and NI-R compared to LD and SD. These results suggest that morphogenesis, flowering, and transcriptional factors are strongly affected by light quality during NI.

Iron deficiency and cadmium (Cd) stress causes a rapid change in plant physiology. The aim of this work was to characterize the effects of Fe supplementation on redox reactions in leguminous plants under Cd toxicity. The experiments were performed in hydroponic nutrient media, using mungbean grown under 300 µM cadmium chloride with or without Fe for 10 days. The Fe concentration in plants grown under Fe deficiency was reduced by the presence of Cd; however, it recovered to control levels after Fe was supplied. Similarly, a very high Cd concentration was observed in plants grown under Fe deficiency in the presence of Cd toxicity but when Fe was supplied the Cd concentration decreased. After 5 days of Fe deficiency, the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione reductase and ascorbate peroxidase) were significantly higher than in plants supplied with Fe in the absence or presence of Cd. However, after 10 days of Fe deficiency, these enzyme activities were severely decreased in the presence of Cd toxicity but increased when Fe was present. The activities of other peroxidase enzymes such as guaiacol peroxidase, syringaldazine peroxidase, polyphenol oxidase and benzidine peroxidase decreased after 10 days under Cd toxicity and were further reduced in the absence of Fe. Furthermore, the level of reduced glutathione and oxidized glutathione increased for the first 5 days under Cd toxicity under Fe deficiency but was reduced after Fe was supplied to Cd-treated plants. The data indicate that supply of Fe contributes to the alleviation of Cd toxicity in redox reaction pathways in mungbean plants., The present study was performed on mungbean to determine the effect of treatment with Cd and Fe for 5 and 10 days on redox reactions. The antioxidative enzymes were decreased 10 days after Fe-Cd treatment but were improved by Fe supplementation. A reduction in peroxidase enzymes was observed 10 days after Fe-Cd treatment but levels were improved by Fe treatment. Fe-nutritional status contributed to the mitigation of Cd toxicity even for longer periods of oxidative stress.

The application of grafting in tomato production has substantially improved tomato quality and yields. It has been demonstrated that humidity plays an important role in the graft healing of seedlings. This study focuses on the optimum relative humidity (RH) conditions for scion and rootstock healing of grafted tomato (Solanum lycopersicum L.) seedlings. Two tomato cultivars, ‘Super Sunload’ and ‘Super Dotaerang’, grafted onto ‘B-Blocking’ rootstock were subjected to one of three RH regimens: 70–80, 80–90, or 90–100%. The results showed that the scions of both cultivars showed apparent wilting under the 70–80 and 80–90% RH treatments. On this basis, the 90–100% RH treatment was subdivided into 95–96, 97–98, and 99–100% RH treatments, which were then applied. Among these subdivided RH treatments, the fresh weights of the scions and rootstocks significantly increased in response to the treatments of 97–98 and 99–100% RH, and the graft union connection of both cultivars was also enhanced after two days of healing. Furthermore, lower levels of endogenous H2O2 and less activity of antioxidant enzymes were observed in both cultivars in response to treatment with 95–96 or 97–98% RH, which indicated that less oxidative stress occurred. Overall, it is suggested that 97–98% is the optimal RH level for the graft healing of tomato seedlings.

In the present study, the functions of vascular connections (graft unions) in the grafted tomato seedlings ( Solanum lycopersicum cv. Super Doterang grafted on cv. B-Blocking) has been monitored with some indicating factors such as transpiration, water uptake rate, sugar content, flower dye distributions between scion and rootstock, and hardness of the grafted unions. In addition, various light qualities have been tested to evaluate the effects on functions of vascular connections particularly on xylem and phloem. Our results depicted that light had a positive effect on the development of grafted unions as well as their functions. The functions of stomata and vascular connections developed approximately 50% particularly in the first five days function monitoring. Moreover, the reduction of sugar content in the scion parts was inhibited instead of the dark condition. The use of the pure red and blue light sources in the acclimating chamber showed difficulties to keep the water balance of the grafted seedlings and the sudden abiotic stress condition (high light intensity) was observed. At day 4 after grafting, the gap between transpirational water loss and water uptake in the FL (fluorescent light) and LED W1R2B1 (light emitting diode white/red/blue) supplying treatment was found to be the smallest, the gap. Our results therefore indicated that light sources from light emitting diodes (LEDs) combined with wave lengths might be beneficial contributions for developing vascular bundles and stomatal behaviors of the grafted seedlings during the wound healing period.

Hyperhydric disorders occur frequently in plant tissues cultured in vitro and cause several morphological and physiological abnormalities. However, a systematic defense response is triggered by hyperhydric conditions. The accumulation of reactive oxygen species (ROS), activities of antioxidant enzymes and their immunoblots, and the proteome-level changes in normal versus hyperhydric shoots of carnation (Dianthus caryophyllus) cultured in vitro were investigated. Total proteins were also extracted from the shoot and analyzed by two-dimensional electrophoresis. Among a total of 700 spots detected, only 40 had significant changes in abundance in the hyperhydric compared to the normal shoots, which were further identified by a mass spectrometer (MALDI-TOF MS). Most of them were involved in photosynthesis, RNA processing, and general metabolisms, while the rest were involved in secondary metabolic processes. These identified proteins in carnation shoots may provide novel evidences for stress tolerance against hyperhydricity.

This study investigated the effects of silicon (Si) nutrition on hydroponically grown Zinnia elegans under salinity stress. In this study, six treatments, the control (basal nutrients without NaCl or Si), Si 50 (1.8 mM), Si 100 (3.6 mM), NaCl 50 (50 mM), Si 50 + NaCl 50 (1.8 mM Si; 50 mM NaCl), and Si 100 + NaCl 50 (Si-3.6 mM + NaCl-50 mM), were employed. After 15 days of treatment, growth parameters, biochemical measurements, and antioxidant enzyme activities were examined. Salinity stress significantly reduced plant growth, biomass, photosynthetic parameters, and pigments, and increased the electrolyte leakage potential (ELP), lipid peroxidation, and hydrogen peroxide level. Interestingly, with Si supplementation, Z. elegans recovered from salinity stress. Si enhanced growth and photosynthesis, and prevented the decomposition of photosynthetic pigments. Moreover, the addition of Si increased membrane integrity, thereby reducing the ELP and lipid peroxidation levels under salinity stress. Furthermore, Si modulated the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) in scavenging excess reactive oxygen species (ROS). Additionally, Si increased the macronutrient and micronutrient contents. Therefore, augmentation with Si provided salinity resistance and enhanced the growth of Z. elegans.

Although silicon (Si) is not considered as an essential element, it is beneficial to the plant growth. Its effect is more evident under abiotic and biotic stress conditions. The objective of this study is to investigate the role of Si on the in vitro growth and resistance to salt stress of Dianthus caryophyllus ‘Tula’. The experiment was designed as a factorial design with 0, 50, or 100 mg·L−1 of potassium silicate (K2SiO3) in combination with 0, 50, or 100 mM sodium chloride (NaCl). The treatment of 50 mg·L−1 Si improved the growth of plant. However, the treatment of Si at 100 mg·L−1 reduced the growth. Although NaCl retarded the growth, addition of Si along with NaCl to the culture medium mitigated the effect of NaCl. A primary defense line by Si to overcome the photosynthetic depression was apparent from the increased chlorophyll content in the Si + NaCl treatment as compared to the treatment of NaCl alone. Enhancement of growth and resistance to salinity by Si was thought to be due to the modulation in activity of antioxidant enzymes, such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase. Therefore, our results suggested that 50 mg·L−1 Si supplementation could be optimal for improved growth in vitro and enhanced resistance against salinity in D. caryophyllus ‘Tula’.

Silicon is considered an important element in several crops because it improves growth and mitigates biotic and abiotic stress. In this work, the role of silicon in limiting Fe deficiency responses by improving photosynthesis and composition of thylakoid multiprotein complexes (MPCs) has been studied. Two-week-old soybean (Glycine max L.) plants grown hydroponically with a Fe-deficient solution without FeIII-EDTA were fed with 1.0 mM silicon in the form of sodium silicate [Na2SiO3]. Responses to four Si and Fe combined treatments were analyzed after 3 and 5 days. Leaf chlorosis was generated under Fe deficiency, with decreased chlorophyll and carotenoid contents. The negative effects observed were more severe under a prolonged period of Fe deficiency. Biomass and Fe concentration in roots and shoots were largely improved by Si supply under Fe deficiency. The rates of net photosynthesis, transpiration and stomatal conductance were highly improved by the supply of Si under Fe deficiency. MPCs proteins (thylakoid complex proteins) evaluated by the first dimension followed by second-dimensional 2D-BN-SDS-PAGE and MALDI–TOF/TOF–MS observation showed that the Fe deficiency greatly decreased thylakoid MPCs and also resulted in a closure of stomata. However, these impacts of Fe deficiency were largely restored in the presence of silicon. The observed responses to silicon supply in Fe-deficient plants indicate that silicon has a significant role in limiting Fe deficiency responses by improving photosynthesis and composition of thylakoid protein complexes.

Salt stress is a rising threat to crop productivity, among several notable consumed crops tomato is often under threat due to salt stress. In this study, the role of Si in restraining salinity stress responses in root proteome and genes involved in stress tolerance has been studied. Fifteen days old tomato (Lycopersicon esculentum L.) plants grown hydroponically with or without NaCl were fed with 2.5 mM Si in the form of potassium silicate [K2SiO3]. The response to a combined effect of NaCl and Si were studied 5 days after treatment. Proteomic analysis indicated that 40 proteins were differentially expressed under Si and/or salt stress treatments. Twenty-four of them were up-regulated by Si supplements (50 mM +NaCl/+Si) and down-regulated in salt-stressed roots (50 mM +NaCl/−Si), and these proteins were mostly associated with stress responses, plant hormones and transcriptional regulations. The rest of them belong to other secondary metabolites. Moreover, 17 differentially expressed proteins (25 mM +NaCl/+Si), up-regulated in the Si treatments, were mostly related to stress responses, plant hormones and cellular biosynthesis, and the rest of the proteins were related to transcriptional regulation, RNA binding and other secondary metabolisms. In addition, 17 protein spots were observed absent in salinity-stressed roots (25/or 50 mM +NaCl/−Si). Moreover, the important genes associated with salt stress responses (leDREB-1, leDREB-2 and leDREB-3), antioxidants (leAPX, leSOD and leCAT genes) and Si transport (leLsi-1, leLsi-2 and leLsi-3) were analyzed by the real-time polymerase chain reaction. The physiological data such as thiobarbituric acid reactive substances, superoxide dismutase as an oxidative stress marker and concentration of Si all correlated well with proteomic and gene expression data. The observed responses to Si supply in salt stressed plants indicate that the Si has a substantial role in alleviating the salinity stress responses by improving the root proteome and activating important genes responsible for stress tolerance.

An understanding of the mechanism underlying fruit ripening is critical for fruit quality improvement. Although post-harvest ethylene application is known to enhance the onset of fruit ripening, exact mechanisms remain unclear. To characterize the fruit ripening process and mechanism, we investigated the effects of exposing kiwifruit cultivars ‘Hayward’ and ‘Gamrok’ to exogenous ethylene treatment post-harvest using comprehensive proteomic analyses. Comparative two-dimensional gel electrophoresis showed that most of the proteins aggregated in ethylene-treated samples compared to the control (non-treated). We observed that among all ethylene treatments, 95 proteins from ‘Hayward’ and 106 from ‘Gamrok’ were differentially expressed. Interestingly, among the elicited protein successfully identified by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry, 50% from “Hayward’ and 60% from ‘Gamrok’ are associated with fruit ripening. Furthermore, 18% and 10% of proteins, respectively, are associated with defense response, whereas other major proteins are related to protein biosynthesis and photosynthesis/Calvin cycle. Interactions between identified proteins were demonstrated by bioinformatic analysis, providing insights into biological pathways and molecular functions in post-harvest kiwifruit ripening elicited by ethylene application. The present proteomic study in accordance with physiological analysis provides a quantitative evaluation of fruit ripening in response to exogenous ethylene in post-harvest kiwifruit.

The present study depicted the role of silicon in limiting the hyperhydricity in shoot cultures of carnation through proteomic analysis. Four-week-old healthy shoot cultures of carnation "Purple Beauty" were sub-cultured on Murashige and Skoog medium followed with four treatments, viz. control (-Si/-Hyperhydricity), hyperhydric with no silicon treatment (-Si/+Hyperhydricity), hyperhydric with silicon treatment (+Si/+Hyperhydricity), and only silicon treated with no hyperhydricity (+Si/-Hyperhydricity). Comparing to control morphological features of hyperhydric carnations showed significantly fragile, bushy and lustrous leaf nature, while Si supply restored these effects. Proteomic investigation revealed that approximately seventy protein spots were differentially expressed under Si and/or hyperhydric treatments and were either up- or downregulated in abundance depending on their functions. Most of the identified protein spots were related to stress responses, photosynthesis, and signal transduction. Proteomic results were further confirmed through immunoblots by selecting specific proteins such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), PsaA, and PsbA. Moreover, protein-protein interaction was also performed on differentially expressed protein spots using specific bioinformatic tools. In addition, stress markers were analyzed by histochemical localization of hydrogen peroxide (H₂O₂) and singlet oxygen (O₂1-). In addition, the ultrastructure of chloroplasts in hyperhydric leaves significantly resulted in inefficiency of thylakoid lamella with the loss of grana but were recovered in silicon supplemented leaves. The proteomic study together with physiological analysis indicated that Si has a substantial role in upholding the hyperhydricity in in vitro grown carnation shoot cultures.

Tomato plants often grow in saline environments in Mediterranean countries where salt accumulation in the soil is a major abiotic stress that limits its productivity. However, silicon (Si) supplementation has been reported to improve tolerance against several forms of abiotic stress. The primary aim of our study was to investigate, using comparative physiological and proteomic approaches, salinity stress in chloroplasts of tomato under silicon supplementation. Tomato seedlings (Solanum lycopersicum L.) were grown in nutrient media in the presence or absence of NaCl and supplemented with silicon for 5 days. Salinity stress caused oxidative damage, followed by a decrease in silicon concentrations in the leaves of the tomato plants. However, supplementation with silicon had an overall protective effect against this stress. The major physiological parameters measured in our studies including total chlorophyll and carotenoid content were largely decreased under salinity stress, but were recovered in the presence of silicon. Insufficient levels of net-photosynthesis, transpiration and stomatal conductance were also largely improved by silicon supplementation. Proteomics analysis of chloroplasts analyzed by 2D-BN-PAGE (second-dimensional blue native polyacrylamide-gel electrophoresis) revealed a high sensitivity of multiprotein complex proteins (MCPs) such as photosystems I (PSI) and II (PSII) to the presence of saline. A significant reduction in cytochrome b6/f and the ATP-synthase complex was also alleviated by silicon during salinity stress, while the complex forms of light harvesting complex trimers and monomers (LHCs) were rapidly up-regulated. Our results suggest that silicon plays an important role in moderating damage to chloroplasts and their metabolism in saline environments. We therefore hypothesize that tomato plants have a greater capacity for tolerating saline stress through the improvement of photosynthetic metabolism and chloroplast proteome expression after silicon supplementation.

Cadmium signifies a severe threat to crop productivity and green gram is a notably iron sensitive plant which shows considerable variation towards cadmium stress. A gel-based proteomics analysis was performed with the roots of green gram exposed to iron and cadmium combined treatments. The resulting data show that twenty three proteins were down-regulated in iron-deprived roots either in the absence (−Fe/−Cd) or presence (−Fe/+Cd) of cadmium. These down-regulated proteins were however well expressed in roots under iron sufficient conditions, even in the presence of cadmium (+Fe/+Cd). The functional classification of these proteins determined that 21% of the proteins are associated with nutrient metabolism. The other proteins in higher quantities are involved in either transcription or translation regulation, and the rest are involved in biosynthesis metabolism, antioxidant pathways, molecular chaperones and stress response. On the other hand, several protein spots were also absent in roots in response to iron deprivation either in absence (−Fe/−Cd) or presence (−Fe/+Cd) of cadmium but were well expressed in the presence of iron (+Fe/+Cd). Results suggest that green gram plants exposed to cadmium stress are able to change the nutrient metabolic balance in roots, but in the mean time regulate cadmium toxicity through iron supplements.

The objective of this study was to investigate the response of light emitting diodes (LEDs) at different light intensities (70 and 80 for green LEDs, 88 and 238 for red LEDs and 80 and 238 mol m(-2) s(-1) for blue LEDs) at three wavelengths in lettuce leaves. Lettuce leaves were exposed to (522 nm), red (639 nm) and blue (470 nm) LEDs of different light intensities. Thylakoid multiprotein complex proteins and photosynthetic metabolism were then investigated. Biomass and photosynthetic parameters increased with an increasing light intensity under blue LED illumination and decreased when illuminated with red and green LEDs with decreased light intensity. The expression of multiprotein complex proteins including PSII-core dimer and PSII-core monomer using blue LEDs illumination was higher at higher light intensity (238 mol m(-2) s(-1)) and was lowered with decreased light intensity (70-80 mol m(-2) s(-1)). The responses of chloroplast sub-compartment proteins, including those active in stomatal opening and closing, and leaf physiological responses at different light intensities, indicated induced growth enhancement upon illumination with blue LEDs. High intensity blue LEDs promote plant growth by controlling the integrity of chloroplast proteins that optimize photosynthetic performance in the natural environment.

In order to characterize the significance of sulfur (S) nutrition in protein expression under iron (Fe)-deficient conditions, gel-based proteomic analysis was performed with the leaves of Brassica napus exposed to S and Fe combined treatments: sufficient in S and Fe (+S/+Fe, control), sufficient S but Fe deprived (+S/−Fe), deprived S but sufficient Fe (−S/+Fe), and deprived S and Fe (−S/−Fe). The resulting data showed that 15 proteins were down-regulated due to production of oxidative damage as indicated by H2O2 and O2−1 localizations and due to leaf chlorosis in leaves in S-deprived leaves either in presence (−S/+Fe) or absence of Fe (−S/−Fe), whereas these down-regulated proteins were well expressed in the presence of S (+S/−Fe) compared to control (+S/+Fe). In addition, two proteins were up-regulated under S-deprived condition in presence (−S/+Fe) and absence of (−S/−Fe) Fe. The functional classification of these identified proteins was estimated that 40 % of the proteins belong to chloroplast precursor, and rest of the proteins belongs to hypothetical proteins, RNA binding, secondary metabolism and unknown proteins. On the other hand, five protein spots from S deprived (−S/+Fe) and ten spots from Fe deprived (−S/−Fe) conditions were absent, whereas they were well expressed in presence of S (+S/−Fe) compared to control plants (+S/+Fe). These results suggest that sulfur nutrition plays an important role in alleviating protein damage in Fe-deficient plants and adaptation to Fe-deficiency in oilseed rape.