Growth, biochemical modifications and proline metabolism in Helianthus annuus L. as induced by drought stress

In the present investigation, two watering treatments, viz., 100% and 60% field capacity (FC) were used to understand the effects of water deficit on early growth, biomass allocation, pigment and biochemical constituents and proline metabolism of five varieties of Sunflower (Helianthus annuus L.) plants. We found that there was a significant difference in early growth, dry matter accumulation, pigment, biochemical constituents and proline metabolism among the five varieties. The root length, shoot length, total leaf area, fresh and dry weight, chlorophyll a, b, total chlorophyll and carotenoid were significantly reduced under water stress treatments. Water stress increased the proline, free amino acid and glycinebetaine contents along with increased activity of γ-glutamyl kinase but the activity of proline oxidase reduced as a consequence of water stress.     

Antioxidant potential and indole alkaloid profile variations with water deficits along different parts of two varieties of Catharanthus roseus

The variations in antioxidant potentials and indole alkaloid content were studied in the present investigation, in two varieties (rosea and alba) of Catharanthus roseus, an important herb used in traditional as well as modern medicine, exposed to water deficit stress. The antioxidant and alkaloid profiles were estimated from root, stem, leaf, flowers and pods. The antioxidant potentials were examined in terms of non-enzymatic antioxidant molecules and activities of antioxidant enzymes. The non-enzymatic antioxidant molecules studied were ascorbic acid (AA), -tocopherol (-toc) and reduced glutathione (GSH). The estimated antioxidant enzymes were superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO). The antioxidant concentrations and activities of antioxidant enzymes were high under water deficit stress in all parts of the plants. Indole alkaloid content was high in the roots of rosea variety in response to stress when compared to alba variety.     

Relative efficacy of water use in five varieties of Abelmoschus esculentus (L.) Moench. under water-limited conditions

In the present investigation, five varieties of okra (Abelmoschus esculentus (L.) Moench.) were screened for their water use efficiency under two water regimes, viz., 60% and 100% filed capacity. Drought stress was imposed at 60% field capacity from 30 to 70 days after sowing, while the control pots were maintained at 100% field capacity throughout the period of entire growth. Biomass and yield, leaf area duration, cumulative water transpired water use efficiency, net assimilation rate, mean transpiration rate and harvest index under water deficit level were measured. Water use efficiency significantly increases in all the okra varieties under water-limited environment. Drought stress decreased the biomass and yield, leaf area duration, cumulative water transpired, net assimilation rate, mean transpiration rate and harvest index in the okra varieties studied. But among the varieties, variety JK Haritha showed better results. None of the varieties studied had showed increased drought tolerance than the control.     

Effects of water stress and high temperature on photosynthetic rates of two species of Prosopis

The main aim of this research was to compare the photosynthetic responses of two species of Prosopis, Prosopis chilensis (algarrobo) and Prosopis tamarugo (tamarugo) subjected to heat and water stress, to determine how heat shock or water deficit, either individually or combined, affect the photosynthesis of these two species. The photosynthetic rates expressed as a function of photon flow density (PFD) were determined by the O(2) liberated, in seedlings of tamarugo and algarrobo subjected to two water potentials: -0.3MPa and -2.5MPa and to three temperatures: 25 degrees C, 35 degrees C and 40 degrees C. Light response curves were constructed to obtain light compensation and light saturation points, maximum photosynthetic rates, quantum yields and dark respiration rates. The photochemical efficiency as the F(v)/F(m) ratio and the amount of RUBISCO were also determined under heat shock, water deficit, and under the combined action of both stress. Photosynthetic rates at a light intensity higher than 500mumole photons m(-2)s(-1) were not significantly different (P>0.05) between species when measured at 25 degrees C under the same water potential. The maximum photosynthetic rates decreased with temperature in both species and with water deficit in algarrobo. At 40 degrees C and -2.5MPa, the photosynthetic rate of algarrobo fell to 72% of that of tamarugo. The quantum yield decreased in algarrobo with temperature and water deficit and it was reduced by 50% when the conditions were 40 degrees C and -2.5MPa. Dark respiration increased by 62% respect to the control at 40 degrees C in tamarugo while remained unchanged in algarrobo. The photochemical efficiency decreased with both, high temperature and water deficit, without differences between species. RUBISCO content increased in algarrobo 35 degrees C. Water deficit reduced the amount of RUBISCO in both species. The results of this work support the conclusion that in both Prosopis species, the interaction between high temperature and water deficit affects photosynthesis responses greater than each individual stress, and that the interactive effect is more pronounce in algarrobo than in tamarugo.     

Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation

The effect of enhanced UV-B radiation on buckwheat (Fagopyrum esculentum Moench. variety 'Darja'), an important high elevation crop, was studied in order to estimate its vulnerability in changing UV-B environment. Plants were grown in outdoor experiments from July to October under reduced and ambient UV-B levels, and an UV-B level simulating 17% ozone depletion in Ljubljana. During the development the following parameters were monitored: light saturated photosynthetic activity, transpiration, potential and effective photochemical efficiencies of photosystem II, the contents of photosynthetic pigments and methanol soluble UV-B absorbing compounds. At the end of the experiment, growth rate and production of seeds were estimated. In the following growth season the seeds collected from plants exposed to different UV-B treatments were tested for germination capacity. Total UV-B absorbing compounds during plant development were increased by UV-B radiation, photosynthetic pigments (chlorophyll a and b and carotenoids) decreased. Photosynthetic rate was lowered in an early stage of development. UV-B treatment resulted in the increase in the transpiration rate and consequently the decrease in water use efficiency (WUE). The disturbances in water economy and in photosynthesis affected the reproduction potential negatively; the production of seeds in plants cultivated under ambient and enhanced UV-B was 57 and 39% of the production of specimens treated with reduced UV-B, respectively. The germination of seeds collected from treated plants revealed on average about 95% success, independently of the treatment, but the time needed for germination was the shortest for seeds developed under enhanced UV-B level treatment. Enhanced UV-B radiation affected water relations and production of buckwheat, but not the potential of seeds for germination.     

Differences in the response of wheat, soybean and lettuce to reduced blue radiation

Although many fundamental blue light responses have been identified, blue light dose-response curves are not well characterized. We studied the growth and development of soybean, wheat and lettuce plants under high-pressure sodium (HPS) and metal halide (MH) lamps with yellow filters creating five fractions of blue light. The blue light fractions obtained were < 0.1, 2 and 6% under HPS lamps, and 6, 12 and 26% under MH lamps. Studies utilizing both lamp types were done at two photosynthetic photon flux levels, 200 and 500 mumol m-2 s-1 under a 16 h photoperiod. Phytochrome photoequilibria was nearly identical among treatments. The blue light effect on dry mass, stem length, leaf area, specific leaf area and tillering/branching was species dependent. For these parameters, wheat did not respond to blue light, but lettuce was highly sensitive to blue light fraction between 0 and 6% blue. Soybean stem length decreased and leaf area increased up to 6% blue, but total dry mass was unchanged. The blue light fraction determined the stem elongation response in soybean, whereas the absolute amount of blue light determined the stem elongation response in lettuce. The data indicate that lettuce growth and development requires blue light, but soybean and wheat may not.     

Screening of Eight Eucalypt Genotypes (Eucalyptus sp.) for Water Deficit Tolerance Using Multivariate Cluster Analysis

The present study evaluated eight genotypes of river red gum (Eucalyptus camaldulensis Dehnh.) and a hybrid (E. camaldulensis?×?E. urophylla) for mannitol-induced water deficit (WD) under photoautotrophic conditions using multivariate cluster analysis. Shoot height, plant dry weight, and chlorophyll a content in hybrid genotypes, 58H2 and 27A2, were maintained when exposed to 200 mM mannitol for 14 days. In addition, the diminution of photosynthetic abilities, i.e. maximum quantum yield of PSII, photon yield of PSII, photochemical quenching, and net photosynthetic rate, under WD was minimal in hybrid genotypes compared to that in selection clones of E. camaldulensis. Under WD condition, there was greater accumulation of proline in all genotypes. A positive relationship was observed between physiological and morphological attributes under WD stress. Using Ward’s cluster analysis, hybrid genotypes—H4, 58H2, and 27A2—were classified as water deficit tolerant.     

Comparative Evaluation of the Effects of Bone Powder and Calcium Phosphate on Plant Growth and Development

The present study aimed to elucidate the effectiveness of inorganic element composition (except for calcium and phosphorus) of bone powder (BP) on some morphological (root and shoot length and dry weight) and biochemical (protein, sugar, chlorophyll, and inorganic element contents) parameters in bean seedlings. For this, BP was compared with calcium phosphate (CP), which is used as calcium and phosphorus source. Bone powder solutions (BPS) (0.5, 1, 1.5, and 2%) and CP solution (0.1 M) were applied to growing media of 12-day bean seedlings. Seedlings were harvested on 20th day. Both BPS and CP treatments significantly stimulated plant growth and increased dry weight, pigment, protein, and sugar contents compared to control seedlings; however, BPS treatments were found to be more effective than CP treatment. The best stimulatory effect on plant growth was determined at 1.5% concentration of BPS. Besides, BP treatment significantly increased contents of K, S, Fe, Zn, Mg, Mn, and Cu compared to control and CP-treated seedlings. This result clearly elucidated that the other elements existing in structure of BP also participated in plant structure, and they played important roles on growth and development in bean seedlings. It is possible to say that BP

may be used as an important source of the other inorganic elements as well as Ca and P in agriculture studies for improving of plant growth and productivity. This is the first report revealing the effect of BP on inorganic element content of plants.     

Polypeptide changes induced by salt stress, water deficit, and osmotic stress in barley roots: a comparison using two-dimensional gel electrophoresis

Two-dimensional polyacrylamide gel electrophoresis was used to analyze and compare the effects of short term treatments (24 h) of salt stress, water deficit (desiccation), and osmotic stress (polyethylene glycol and mannitol) on protein synthesis in roots of barley seedlings (Hordeum vulgare L. cv. CM 72). These comparisons were made to determine if the polypeptides of Mr 26,000 and 27,000 and pI of 6.3 and 6.5 that were observed previously to increase significantly with salt stress (Plant Physiol. 1987, 83 517-524) also increased with water deficit and osmotic stress. The polypeptide patterns for control- and stress-treated plants were qualitatively similar, but the net synthesis of a number of polypeptides was quantitatively altered by each of the stress treatments. Of the polypeptide changes induced by the stress treatments, many were unique to a specific stress. Other polypeptide changes were common between two or more of the stress treatments. Only one polypeptide change, a decrease, was common to all of the stress treatments. An important finding was that polypeptides that increased significantly in response to salt stress did not increase in response to water deficit or osmotic stress.     

The Use of UV Radiation to Control the Architecture of Salvia splendens Plants. I. Effects on Plant Growth, Water Relations and Gas Exchange

In experiments with Salvia splendens plants grown in the greenhouse we evaluated the possible use of irradiation with unfiltered UV (UVA + UVB + UVC) lamps for the control of plant growth. The effect of UV Irradiation on the growth of S. splendens plants in the grcenhouse was closely dependent on the growing season and the level of available photosynthetically active radiation. In summer UV treatments were ineffective, but in the low light conditions of winter UV irradiation inhibited the growth via both photomorphogenic and photosynthetic effects. The reduction of stomatal conductance and expansion growth, which in turn depressed photosynthesis and dry matter accumulation, were not a consequence of an impairment of plant water status but appeared to be a direct UV effect on stomata and cell wall rheological propertles. Our findings suggest that the use of unfiltered UV irradiation could become an effective tool for the regulation of growth in greenhouse crops, particularly during the poor light conditions of the winter season.     

Alleviation of adverse effects of drought stress on growth and some potential physiological attributes in maize (Zea mays L.) by seed electromagnetic treatment

Effects of varying preseed magnetic treatments on growth, chlorophyll pigments, photosynthesis, water relation attributes, fluorescence and levels of osmoprotectants in maize plants were tested under normal and drought stress conditions. Seeds of two maize cultivars were treated with different (T0 [0 mT], T1 [100 mT for 5 min], T2 [100 mT for 10 min], T3 [150 mT for 5 min] and T4 [150 mT for 10 min]) electromagnetic treatments. Drought stress considerably suppressed growth, chlorophyll a and b pigments, leaf water potential, photosynthetic rate (A), stomatal conductance (g(s)) and substomatal CO(2) concentration (C(i)), while it increased leaf glycinebetaine and proline accumulation in both maize cultivars. However, pretreated seeds with different magnetic treatments significantly alleviated the drought-induced adverse effects on growth by improving chlorophyll a, A, E, g(s), C(i) and photochemical quenching and nonphotochemical quenching, while it had no significant effect on other attributes. However, different magnetic treatments negatively affected the g(s) and C(i) particularly in cv. Agaiti-2002 under drought stress conditions. Of all magnetic treatments, 100 and 150 mT for 10 min were most effective in alleviating the drought-induced adverse effects. Overall, preseed electromagnetic treatments could be used to minimize the drought-induced adverse effects on different crop plants.     

Mass spectrometric analysis of the 13C/12C abundance ratios in vine plants and wines depending on regional climate factors (Krasnodar krai and Rostov oblast, Russia)

Distribution of ¹³C/¹²C isotopes in vegetative (roots, grapevine, leaves) and generative (berries) parts of vine plants of the West European genetically different varieties Cabernet Sauvignon and Aligoté growing on soils of Krasnodar krai and Rostov oblast, as well as autochthonous varieties Sibirkovy and Krasnostop Zolotovsky growing in Rostov oblast, has been studied using isotopic mass spectrometry methods. It has been shown that the variations of δ¹³C values in plant tissues and berries are related to the climatic conditions of plant growth: moisture (a sum of annual precipitation) and temperature (a sum of annual effective temperatures). The carbon isotope ratios of vegetative and generative parts of vine plants have been found to be noticeably affected by vine varieties. The different ¹³C contents in ethanol produced from wine of the Aligoté and Cabernet Sauvignon varieties grown in two Russian vineyard regions are due to vine growth conditions, variety attribution and wine production techniques. An analytically significant parameter determined as exemplified by the Aligoté and Cabernet Sauvignon varieties in fermentation of vine harvested in different seasons and in both vineyard regions was an increased ¹³C content in ethanol with respect to dry (non-volatile) residue in wine after distillation of ethanol. This characteristic has been determined by a systematic difference of about 1–2‰ between the δ¹³C value of ethanol and the dry residue. A relative constancy in the carbon isotope composition of ethanol and of the dry residue in the final product is the basis for determining the authenticity of grape wines by means of isotopic mass spectrometry irrespective of natural factors.     

The Effects of UV‐B Radiation Intensity on Biochemical Parameters and Active Ingredients in Flowers of Qi Chrysanthemum and Huai Chrysanthemum

The article studied UV‐B effects on biochemical parameters and active ingredients in flowers of Qi chrysanthemum and Huai chrysanthemum during the bud stage. The experiment included four UV‐B radiation levels (CK, ambient UV‐B; T1, T2 and T3 indicated a 5%, 10% and 15% increase in ambient UV‐B_BE, respectively) to determine the optimal UV‐B radiation intensity in regulating active ingredients level in flowers of two chrysanthemum varieties. Flower dry weight of two cultivars was not affected by UV‐B radiation under experimental conditions reported here. UV‐B treatments significantly increased the rate of superoxide radical production, hydrogen peroxide (H₂O₂) (except for T1) and malondialdehyde concentration in flowers of Huai chrysanthemum and H₂O₂ concentration in flowers of Qi chrysanthemum. T2 and T3 treatments induced a significant increase in phenylalanine ammonia lyase enzyme (PAL) activity, anthocyanins, proline, ascorbic acid, chlorogenic acid and flavone content in flowers of two chrysanthemum varieties, and there were no significant differences in PAL activity, ascorbic acid, flavone and chlorogenic acid content between the two treatments. These results indicated that appropriate UV‐B radiation intensity did not result in the decrease in flower yield, and could regulate PAL activity and increase active ingredients content in flowers of two chrysanthemum varieties.     

Pseudomonas fluorescens enhances biomass yield and ajmalicine production in Catharanthus roseus under water deficit stress

The effect of plant growth promoting rhizobacteria (PGPR) like Pseudomonas fluorescens on growth parameters and the production of ajmalicine were investigated in Catharanthus roseus under drought stress. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with Pseudomonas fluorescens at 1mgl(-1) and 1mgl(-1)Pseudomonas fluorescens alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stress decreased the growth parameters and increased the ajmalicine content. But the treatment with Pseudomonas fluorescens enhanced the growth parameters under drought stress and partially ameliorated the drought induced growth inhibition by increasing the fresh and dry weights significantly. The ajmalicine content was again increased due to Pseudomonas fluorescens treatment to the drought stressed plants. From the results of this investigation, it can be concluded that, the seedling treatments of native PGPRs can be used as a good tool in the enhancement of biomass yield and alkaloid contents in medicinal plants, as it provides an eco-friendly approach and can be used as an agent in water deficit stress amelioration.     

Effect of ultraviolet-B radiation on salt marsh vegetation: Trends of the genus Salicornia along the Americas

The effects of natural UV-B radiation on growth, photosynthetic and photoprotective pigment composition of different Salicornia species were analyzed in salt marshes at three different sites along the Americas (Puerto Rico, southern Brazil and Patagonia, Argentina). Plants were exposed to different levels of UV-B radiation for 1-2 years in situ as well as in outdoor garden UV-B exclusion experiments. Different UV-B levels were obtained by covering plants with UV-B opaque (blocked 93-100% of ambient UV-B) and UV-B attenuating (near-ambient) filters (reduced 20-25% of UV-B). Unfiltered plants were exposed to natural irradiance. UV-B filters had significant effects on temperature and photosynthetic pigments (due to changes in PAR; 400-700 nm). The growth of Salicornia species was inhibited after 35 to 88 days of exposure to mean UV-B radiation dosages between 3.6 and 4.1 kJ m(-2) day(-1). The highest number of branches on the main shoot (S. bigelovii and S. gaudichaudiana) and longest total length of the branches (S. gaudichaudiana) were observed in the UV-B opaque treatment. Salicornia species responded to increasing levels of UV-B radiation by increasing the amount of UV-B absorbing pigments up to 330%. Chromatographic analyses of seedlings and adult S. bigelovii plants found seven different UV-B absorbing flavonoids that are likely to serve as UV-B filtering pigments. No evidence of differential sensitivity or resilience to UV-B radiation was found between Salicornia species from low-mid latitudes and a previously published study of a high-latitude population.     

Evidence for yellow light suppression of lettuce growth

Researchers studying plant growth under different lamp types often attribute differences in growth to a blue light response. Lettuce plants were grown in six blue light treatments comprising five blue light fractions (0, 2, 6% from high-pressure sodium [HPS] lamps and 6, 12, 26% from metal halide [MH] lamps). Lettuce chlorophyll concentration, dry mass, leaf area and specific leaf area under the HPS and MH 6% blue were significantly different, suggesting wavelengths other than blue and red affected plant growth. Results were reproducible in two replicate studies at each of two photosynthetic photon fluxes, 200 and 500 mumol m-2 s-1. We graphed the data against absolute blue light, phytochrome photoequilibrium, phototropic blue, UV, red:far red, blue:red, blue: far red and 'yellow' light fraction. Only the 'yellow' wavelength range (580-600 nm) explained the differences between the two lamp types.     

Investigation on water consumption characteristics and water use efficiency of poplar under soil water deficits on the Loess Plateau

The water consumption characteristics and water use efficiency (WUE) of poplar (Populus simonii) were investigated under the condition of three different soil water regimes, which were 70%, 55% and 40% of field capacity (FC), respectively. The results showed that water potential, water content, photosynthetic rate, WUE of leaves, and plant growth rate decreased significantly with reduction in soil water content. At the level of adequate and medium soil water content, rapid growth and biomass accumulation in poplar occurred during May and June, whereas this phenomenon occurred only during May under severe soil drought condition. Total water consumption and biomass growth were the greatest under adequate soil water condition, decreased under medium soil drought condition, and lowest under severe soil drought condition. Total WUE was the highest under medium soil water condition and lowest under severe soil condition. Changing patterns of water consumption for daily rate, every 10-day rate, and month rate were quite different under these three soil water regimes. For all these three treatments, the highest monthly water consumption rate occurred during July and June. The highest water consumption over a 10-day period was during in the second 10 days of July, the first 10 days of July, and the last 10 days of June for these three treatments, respectively. The day for the highest water consumption in the medium and severe drought treatments occurred 1 or 2 months earlier than the adequate soil water treatment. The daily time for the greatest water consumption was different throughout the life span of poplar under these soil water levels. According to these results, we concluded that poplar did not have the characteristics of drought-resistance plants, and we do not recommend that this tree species be planted over a wider range of the Loess Plateau in China.     

Light energy conversion with pheophytina monolayer at the SnO2 optically transparent electrode

The photoelectrochemical, absorption and fluorescence properties of pheophytin a mono- and multilayers, deposited on optically transparent tin oxide electrodes and quartz slides were investigated. Spectra of photocurrents coincided with the absorption spectra of photosynthetic pigment in monolayers at the SnO₂/solution interfaces. The anodic and cathodic photocurrents were measured at various electrode potentials. Effects of pH, electrode potentials, and concentration of redox reagents on the conversion of solar energy in monolayers on optically transparent electrodes are discussed. The absorption and fluorescence spectral characteristics, and fluorescence lifetime measurements of pheophytina in monolayers and thin films are also discussed in view of the aggregation properties of the photosynthetic pigment. The thermodynamics of adsorption of large amphiphilic compounds at the interface between two immiscible liquids is considered. The adsorption behavior of pheophytin a dissolved in different solvents is investigated. The thermodynamic parameters of pheophytin a adsorption at octane/water and benzene/water interfaces were determined.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Photobiological Interactions of Blue Light and Photosynthetic Photon Flux: Effects of Monochromatic and Broad‐Spectrum Light Sources

Photosynthesis (Pn) and photomorphogenesis (Pm) are affected by light quality, light intensity and photoperiod. Although blue light (BL) is necessary for normal development, it is less efficient in driving Pn than other wavelengths of photosynthetically active radiation. The effects of BL on Pm are highly species dependent. Here we report the interacting effects of BL and photosynthetic photon flux (PPF) on growth and development of lettuce, radish and pepper. We used light‐emitting diode (LED) arrays to provide BL fractions from 11% to 28% under broad‐spectrum white LEDs, and from 0.3% to 92% under monochromatic LEDs. All treatments were replicated three times at each of two PPFs (200 and 500 μmol m^?2 s^?1). Other than light quality, environmental conditions were uniformly maintained across chambers. Regardless of PPF, BL was necessary to prevent shade‐avoidance responses in radish and lettuce. For lettuce and radish, increasing BL reduced stem length, and for both species, there were significant interactions of BL with PPF for leaf expansion. Increasing BL reduced petiole length in radish and flower number in pepper. BL minimally affected pepper growth and other developmental parameters. Pepper seedlings were more photobiologically sensitive than older plants. Surprisingly, there were few interactions between monochromatic and broad‐spectrum light sources.     

Effects of water deficit on photosystem II photochemistry and photoprotection during acclimation of lyreleaf sage (Salvia lyrata L.) plants to high light

Acclimation of photosynthetic light reactions to high light requires adjustments in photosystem II (PSII) photochemistry and may be affected by environmental stresses, such as water deficit. In this study, we examined the effects of this stress on PSII photochemistry and photoprotection, with an emphasis on the role of carotenoids and tocopherols, during acclimation of lyreleaf sage (Salvia lyrata L.) plants to high light. Violaxanthin was rapidly converted to zeaxanthin under high light, the de-epoxidation state of the xanthophyll cycle reaching maximum levels of 0.97 after 10 days of high light exposure. Under a higher photoprotective demand caused by water deficit, plants showed significant decreases in beta-carotene and enhanced oxidation of alpha-tocopherol to alpha-tocopherol quinone, which was followed by decreases in the F(v)/F(m) ratio. The levels of beta-carotene decreased more in water-stressed than irrigated plants during acclimation to high light, being particularly degraded (up to 73%) after 14 days of water deficit. Tocopherol levels increased significantly during acclimation to high light, particularly under water deficit, which caused 6.6- and 10-fold increases in alpha-tocopherol and alpha-tocopherol quinone, respectively. We conclude that when xanthophyll cycle-dependent excess energy dissipation could not afford further protection during high light acclimation and the photoprotective demand increased in lyreleaf sage plants by water deficit, enhanced oxidation of alpha-tocopherol and beta-carotene occurred. As stress persisted, enhanced formation of reactive oxygen species might ultimately damage the PSII, as indicated by the reductions in the F(v)/F(m) ratio.