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Ozone (O 3 ) is an oxidative pollutant that significantly threatens plant development and ecological dynamics. The present study explores the impact of O 3 on Moringa (Moringa oleifera) ecotypes when exposed to ambient and elevated O 3 levels. Elevated O 3 concentrations resulted in significant reductions in total biomass for all ecotypes. Photosynthetic parameters, including stomatal conductance (g sto ), CO 2 assimilation (P n ), and carboxylation efficiency (K), decreased under elevated O 3 in some ecotypes, indicating a detrimental effect on carbon assimilation. Nonstructural carbohydrate (NSC) levels in roots varied among ecotypes, with significant reductions in starch content observed under elevated O 3 , suggesting a potential shift towards soluble sugar accumulation and reallocation for antioxidant defense. Secondary metabolite analysis revealed increased polyphenol production, particularly quercetin derivatives, under elevated O 3 in specific ecotypes, highlighting their role in mitigating oxidative stress. Interestingly, the glucosinolate content also varied, with some ecotypes exhibiting increased levels, suggesting a complex regulatory mechanism in response to O 3 exposure. The study underscores the intrinsic variability among Moringa ecotypes in response to O 3 stress, emphasizing the importance of genetic diversity for adaptation. The findings indicate that Moringa's metabolic plasticity, including shifts in NSC and SM production, plays a crucial role in its defense mechanisms against O 3 -induced oxidative stress. These insights are vital for optimizing the cultivation and utilization of Moringa in diverse environmental conditions, particularly in regions with elevated O 3 levels., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Background and Aims: The development of Arundo donax as a biomass crop for use on drought-prone marginal lands in areas with warm to hot climates is constrained by the lack of variation within this species. We investigated the effect of morphological and physiological variation on growth and tolerance to drought under field conditions in three ecotypes of A. donax collected from habitats representing a climate gradient: a pre-desert in Morocco, a semi-arid Mediterranean climate in southern Italy and a warm sub-humid region of central Italy., Methods: The three A. donax ecotypes were grown under irrigated and rain-fed conditions in a common garden field trial in a region with a semi-arid Mediterranean climate. Physiological and morphological characteristics, and carbohydrate metabolism of the ecotypes were recorded to establish which traits were associated with yield and/or drought tolerance., Key Results: Variation was observed between the A. donax ecotypes. The ecotype from the most arid habitat produced the highest biomass yield. Stem height and the retention of photosynthetic capacity later in the year were key traits associated with differences in biomass yield. The downregulation of photosynthetic capacity was not associated with changes in foliar concentrations of sugars or starch. Rain-fed plants maintained photosynthesis and growth later in the year compared with irrigated plants that began to senescence earlier, thus minimizing the difference in yield. Effective stomatal control prevented excessive water loss, and the emission of isoprene stabilized photosynthetic membranes under drought and heat stress in A. donax plants grown under rain-fed conditions without supplementary irrigation., Conclusions: Arundo donax is well adapted to cultivation in drought-prone areas with warm to hot climates. None of the A. donax ecotypes exhibited all of the desired traits consistent with an 'ideotype'. Breeding or genetic (identification of quantitative trait loci) improvement of A. donax should select ecotypes on the basis of stem morphology and the retention of photosynthetic capacity., (© The Author(s) 2018. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Arundo donax has been identified as an important biomass and biofuel crop. Yet, there has been little research on photosynthetic and metabolic traits, which sustain the high productivity of A. donax under drought conditions. This study determined phenotypic differences between two A. donax ecotypes coming from stands with contrasting adaptation to dry climate. We hypothesized that the Bulgarian (BG) ecotype, adapted to drier conditions, exhibits greater drought tolerance than the Italian (IT) ecotype, adapted to a more mesic environment. Under well-watered conditions the BG ecotype was characterized by higher photosynthesis, mesophyll conductance, intrinsic water use efficiency, PSII efficiency, isoprene emission rate and carotenoids, whereas the IT ecotype showed higher levels of hydroxycinnamates. Photosynthesis of water-stressed plants was mainly limited by diffusional resistance to CO2 in BG, and by biochemistry in IT. Recovery of photosynthesis was more rapid and complete in BG than in IT, which may indicate better stability of the photosynthetic apparatus associated to enhanced induction of volatile and non-volatile isoprenoids and phenylpropanoid biosynthesis. This study shows that a large phenotypic plasticity among A. donax ecotypes exists, and may be exploited to compensate for the low genetic variability of this species when selecting plant productivity in constrained environments., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Photosynthetic performance and the expression of genes involved in light signaling and the biosynthesis of isoprenoids and phenylpropanoids were analysed in green ('Tigullio', TIG) and red ('Red Rubin', RR) basil. The aim was to detect the physiological and molecular response mechanisms to high sunlight. The attenuation of blue-green light by epidermal anthocyanins was shown to evoke shade-avoidance responses with consequential effects on leaf morpho-anatomical traits and gas exchange performance. Red basil had a lower mesophyll conductance, partially compensated by the less effective control of stomatal movements, in comparison with TIG. Photosynthesis decreased more in TIG than in RR in high sunlight, because of larger stomatal limitations and the transient impairment of PSII photochemistry. The methylerythritol 4-phosphate pathway promoted above all the synthesis and de-epoxidation of violaxanthin-cycle pigments in TIG and of neoxanthin and lutein in RR. This enabled the green leaves to process the excess radiant energy effectively, and the red leaves to optimize light harvesting and photoprotection. The greater stomatal closure observed in TIG than in RR was due to enhanced abscisic acid (ABA) glucose ester deglucosylation and reduced ABA oxidation, rather than to superior de novo ABA synthesis. This study shows a strong competition between anthocyanin and flavonol biosynthesis, which occurs at the level of genes regulating the oxidation of the C2-C3 bond in the dihydro-flavonoid skeleton., (© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

The putative photoprotective role of foliar anthocyanins continues to attract heated debate. Strikingly different experimental set-ups coupled with a poor knowledge of anthocyanin identity have likely contributed to such disparate opinions. Here, the photosynthetic responses to 30 or 100% solar irradiance were compared in two cultivars of basil, the green-leafed Tigullio (TG) and the purple-leafed Red Rubin (RR). Coumaroyl anthocyanins in RR leaf epidermis significantly mitigated the effects of high light stress. In full sunlight, RR leaves displayed several shade-plant traits; they transferred less energy than did TG to photosystem II (PSII), and non-photochemical quenching was lower. The higher xanthophyll cycle activity in TG was insufficient to prevent inactivation of PSII in full sunlight. However, TG was the more efficient in the shade; RR was far less able to accommodate a large change in irradiance. Investment of carbon to phenylpropanoid biosynthesis was more in RR than in TG in the shade, and was either greatly enhanced in TG or varied little in RR because of high sunlight. The metabolic cost of photoprotection was lower whereas light-induced increase in biomass production was higher in RR than in TG, thus making purple basil the more light tolerant. Purple basil appears indeed to display the conservative resource-use strategy usually observed in highly stress tolerant species. We conclude that the presence of epidermal coumaroyl anthocyanins confers protective benefits under high light, but it is associated with a reduced plasticity to accommodate changing light fluxes as compared with green leaves., (© 2014 Scandinavian Plant Physiology Society.)

Background and Aims: A major challenge in plant ecophysiology is understanding the effects of multiple sub-optimal environmental conditions on plant performance. In most Mediterranean areas soil salinity builds up during the summer because of low availability of soil water coupled with hot temperatures. Although sunlight and soil salinity may strongly interact in determining a plant's performance, this has received relatively little attention., Methods: Two-year-old seedlings of Fraxinus ornus were grown outdoors in pots during a Mediterranean summer in either 45 % (shaded plants) or 100 % (sun plants) sunlight irradiance and were supplied with either deionized water or deionized water plus 75 mm NaCl. Morpho-anatomical traits, water and ionic relations, gas exchange and photosystem II performance, concentrations of individual carotenoids, activity of antioxidant enzymes, concentrations of ascorbic acid and individual polyphenols were measured in leaves. Leaf oxidative stress and damage were estimated by in vivo analysis of stable free radicals and ultrastructural analyses., Key Results: Leaf concentrations of potentially toxic ions did not markedly differ in shaded or sun plants in response to salinity. Leaves of sun plants displayed superior water use efficiency compared with leaves of shaded plants, irrespective of salinity treatment, and had both better stomatal control and higher CO2 carboxylation efficiency than leaves of shaded plants. In the salt-treated groups, the adverse effects of excess midday irradiance were greater in shade than in sun plants. The activity of enzymes responsible for detoxifying hydrogen peroxide decreased in shaded plants and increased in sun plants as a result of salinity stress. In contrast, the activity of guaiacol peroxidase and the concentration of phenylpropanoids increased steeply in response to salinity in shaded plants but were unaffected in sun plants., Conclusions: It is concluded that salinity may constrain the performance of plants growing under partial shading more severely than that of plants growing under full sun during summer. The results suggest co-ordination within the antioxidant defence network aimed at detoxifying salt-induced generation of reactive oxygen species., (© The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Isoprene strengthens thylakoid membranes and scavenges stress-induced oxidative species. The idea that isoprene production might also influence isoprenoid and phenylpropanoid pathways under stress conditions was tested. We used transgenic tobacco to compare physiological and biochemical traits of isoprene-emitting (IE) and non-emitting (NE) plants exposed to severe drought and subsequent re-watering. Photosynthesis was less affected by drought in IE than in NE plants, and higher rates were also observed in IE than in NE plants recovering from drought. Isoprene emission was stimulated by mild drought. Under severe drought, isoprene emission declined, and levels of non-volatile isoprenoids, specifically de-epoxidated xanthophylls and abscisic acid (ABA), were higher in IE than in NE plants. Soluble sugars and phenylpropanoids were also higher in IE plants. After re-watering, IE plants maintained higher levels of metabolites, but isoprene emission was again higher than in unstressed plants. We suggest that isoprene production in transgenic tobacco triggered different responses, depending upon drought severity. Under drought, the observed trade-off between isoprene and non-volatile isoprenoids suggests that in IE plants isoprene acts as a short-term protectant, whereas non-volatile isoprenoids protect against severe, long-term damage. After drought, it is suggested that the capacity to emit isoprene might up-regulate production of non-volatile isoprenoids and phenylpropanoids, which may further protect IE leaves., (© 2014 John Wiley & Sons Ltd.)

We investigated the photosynthetic limitations occurring during dehydration and rehydration of Xerophyta humilis, a poikilochlorophyllous resurrection plant, and whether volatile and non-volatile isoprenoids might be involved in desiccation tolerance. Photosynthesis declined rapidly after dehydration below 85% relative water content (RWC). Raising intercellular CO(2) concentrations during desiccation suggest that the main photosynthetic limitation was photochemical, affecting energy-dependent RuBP regeneration. Imaging fluorescence confirmed that both the number of photosystem II (PSII) functional reaction centres and their efficiency were impaired under progressive dehydration, and revealed the occurrence of heterogeneous photosynthesis during desiccation, being the basal leaf area more resistant to the stress. Full recovery in photosynthetic parameters occurred on rehydration, confirming that photosynthetic limitations were fully reversible and that no permanent damage occurred. During desiccation, zeaxanthin and lutein increased only when photosynthesis had ceased, implying that these isoprenoids do not directly scavenge reactive oxygen species, but rather protect photosynthetic membranes from damage and consequent denaturation. X. humilis was found to emit isoprene, a volatile isoprenoid that acts as a membrane strengthener in plants. Isoprene emission was stimulated by drought and peaked at 80% RWC. We surmise that isoprene and non-volatile isoprenoids cooperate in reducing membrane damage in X. humilis, isoprene being effective when desiccation is moderate while non-volatile isoprenoids operate when water deficit is more extreme., (© 2012 Blackwell Publishing Ltd.)

The effect of different light qualities on growth, photosynthesis, leaf anatomy and isoprenoid emission was studied in two different fast-growing plant systems: a herbaceous crop, tomato (Solanum lycopersicum L.), and a tree, oriental plane (Platanus orientalis L.). Both plant species were subjected to three different light quality regimes: RGB (Red 33%, Green 33%, Blue 33%) and RB (Red 66%, Blue 33%), provided by light emitting diodes (LED); and white light (WL), considered as a control and provided by white fluorescent lamps. Compared to WL, RGB and RB reduced plant height, plant biomass and leaf area. The CO 2 assimilation rate (A) was lower in tomato grown under WL than RGB and RB, while A was similar in oriental plane leaves exposed to the three light regimes. In tomato, stomatal (g s ) and mesophyll (g m ) conductance were higher under RGB and RB compared to WL. In plane, g s was also higher under RGB and RB, while g m was not significantly influenced by different light qualities. In both species, leaf lamina thickness (LT) and stomata size were the anatomical traits most affected by the different light regimes. In tomato, leaf lamina thickness was significantly reduced in RGB and RB leaves, whereas in oriental plane leaf lamina thickness was significantly higher in RGB and RB than in WL leaves. In both species, RB leaves showed bigger stomata size than WL and RGB leaves. Light quality also affected photosynthesis-dependent volatile isoprenoids. In tomato, β-phellandrene was lower under RB and RGB compared to WL. However, RGB and RB stimulated α-pinene, carene and α-terpinene emissions. Oriental plane released about 14 nmol m −2 s −1 isoprene when growing at WL, while the emission was reduced under RGB and even more under RB. In summary, photosynthetic performance, leaf anatomy, biomass production, and volatile isoprenoids are affected by light quality differently in tomato and plane plants. Light quality control may have important applications to modulate plant productivity and increase biosynthesis of useful biochemical compounds. [ABSTRACT FROM AUTHOR]