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To study the light intensity suitable for Bletilla ochracea Schltr., morphology, photosynthetic parameters, and polysaccharide content of seedlings were evaluated under different light intensities. All shade treatments promoted plant growth and net photosynthetic rate while having no significant effect on transpiration rate. The maximum photochemical efficiency and potential photochemical efficiency reached the lowest values under full sunlight. The electron transport rate and photochemical quenching under shade were significantly higher than those under full light, while nonphotochemical quenching was the highest under full light. This indicated that the shade alleviated photoinhibition in summer and improved the utilization of light. B. ochracea could adapt to different light intensities, enhancing photosynthetic efficiency under low light by improving the electron transport and the degree of opened PS? reaction centers, and adapting to high light by increasing heat dissipation. Plant growth, photosynthesis, and polysaccharide accumulation of B. ochracea greatly increased under 76.4% shade. [ABSTRACT FROM AUTHOR]

Through its impact on morphogenesis, light is the key environmental factor that alters plant structural development; however, the understanding how light controls plant growth and developmental processes is still poor and needs further research. For this purpose, a Petri dish and pot experiment was conducted to investigate the effects of different LEDs, i.e., white light (WL), red light (RL), blue light (BL), and orange light (OL) on morphology, gas-exchange parameters, and antioxidant capacity of Brassica napus. Compared with WL, RL significantly promoted plant growth and biomass, contents of photosynthetic pigments, and gas-exchange parameters in comparison to BL and OL. However, RL also helped decline malondialdehyde and proline contents and superoxide anion and peroxide production rate. In contrast, BL and OL significantly reduced plant growth and biomass, gas-exchange attributes and increased the activities of superoxide dismutase and peroxidase in Petri dish as well as in pot experiment. These results suggest that red light could improve plant growth in B. napus plants through activating gas-exchange attributes, reduce reactive oxygen species accumulation, and promote antioxidant capacity. [ABSTRACT FROM AUTHOR]

Our experiment was conducted to understand the effects of foliar sprays of paclobutrazol (PBZ), its mixture with abscisic acid (ABA), or water (control) on leaf carbon-use efficiency (CUEl), photosynthesis, and respiration of Euonymus japonicus seedlings. Plants were pot-grown in a greenhouse. The study revealed that elevated stomatal conductance, mesophyll conductance, and maximum rate of Rubisco carboxylation (Vcmax) in plants treated with PBZ could strongly improve net photosynthetic rate (PN). ABA could antagonize the increase of mesophyll conductance and stomatal conductance by PBZ, thereby inhibiting the improvement of photosynthesis by PBZ. The combination of PBZ and ABA significantly reduced day respiration (Rd) and dark respiration (Rdk), resulting in the increased CUEl, PN/Rd, and PN/Rdk. The increased PN in the PBZ treatment led to slightly increased PN/Rd and CUEl. Thus, the CUEl could be improved by PBZ and its mixtures with ABA by regulating leaf photosynthesis and respiration. [ABSTRACT FROM AUTHOR]

Low temperature (LT) and low irradiation (LI) are common factors posing a great risk to plants. The study aimed to elucidate the effects of LT and LI and recovery on the photosynthetic apparatus, photoinhibition of PSII, and reactive oxygen metabolism of strawberry seedlings. The results showed that strawberry growth slowed down or even stopped and total chlorophyll content, stomatal conductance, net photosynthetic rate, and maximal quantum yield of PSII photochemistry decreased, while intercellular CO2 concentration increased under LI, LT, and combined stress (LL). Additionally, JIP-test showed that compared to LI or LT stress, LL-stressed plants had lower quantum yields and efficiencies and functional antenna size, and higher reaction center activity. Besides, the contents of hydrogen peroxide and malondialdehyde increased, while the activity of superoxide dismutase, peroxidase, and catalase were significantly inhibited compared with the control. After the stress was relieved, the photosynthesis of LL-stressed plants recovered poorly. [ABSTRACT FROM AUTHOR]

Physiological and molecular responses of maize seedlings (Zea mays L. cv. Troinaya sladost) to 5-d drought and rehydration for 48 h were investigated. Plant water status was determined by a new method of water potential measurement in mesophyll cells' apoplast in substomatal cavity (ψwa). Drought caused the changes in water status, plant growth, the rates of photosynthetic CO2/H2O gas exchange, and metabolism of carbohydrates and proline. The increase in carbohydrate and proline content under drought was observed simultaneously with the decline in ψwa. Rewatering of seedlings for 24 and 48 h resulted in restoration of growth, rapid increase in ψwa as well as in the rates of photosynthetic gas exchange, and a sharp decline in the content of soluble sugars and proline. Data on close correspondence between the changes in osmolyte content and ψwa under drought and recovery support the assumption that osmolytes might participate in regulation of ψwa. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is regarded as gaseous signaling molecule in plant response to various biotic and abiotic stresses. In this study, we investigated potential role of H2S in modulating photosynthesis in low light (LL) stress-induced tall fescue (Festuca arundinacea Schreb.) seedlings. Results demonstrated that LL significantly reduced the plant height, leaf width, tiller number, dry mass, turf quality, chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, maximal quantum yield of PSII photochemistry, photochemical efficiency of PSII, photochemical quenching, electron transport rate, and enzymatic activity of ribulose-1,5-bisphosphate carboxylase. Then, these parameters were found to be considerably alleviated by H2S donor application. Moreover, exogenous application of NaHS decreased the concentration of malondialdehyde, increased activities of peroxidase, superoxide dismutase, ascorbate peroxidase, total soluble sugar, soluble protein, and endogenous concentration of H2S. In addition, these responses could be reversed by treatment with hypotaurine (H2S scavenger) and aminooxy acetic acid (H2S biosynthesis inhibitor). These results suggested that H2S was possibly involved in the regulation of photosynthesis to strengthen LL tolerance by maintaining a high level of photochemical efficiency and improving antioxidant enzyme activities in tall fescue. [ABSTRACT FROM AUTHOR]

We studied the effects of melatonin on soybean photosynthesis and seed growth at different developmental stages under drought stress induced by polyethylene glycol in the growth medium. Experimental groups were supplied with a normal nutrient solution after seven days of continuous treatment; overall, five treatments were completed when the early maturity stage was reached. Under normal water supply, melatonin supplementation had no significant effect on the photosynthetic characteristics or soybean seed growth. However, drought stress reduced leaf relative water content, chlorophyll content, and relative photosynthetic gas-exchange parameters, while it increased a leaf content of osmoregulatory substances, antioxidant-related enzyme activities, and seed growth-related indicators. Compared to the drought-stressed group, the melatonin treatment under drought stress improved the above indicators; specifically, melatonin effectively increased the photosynthetic rate, 100-seed mass, and total seed mass per plant. All the effects were most significant during the first seven days after the early seed-filling stage. [ABSTRACT FROM AUTHOR]

Sinopodophyllum hexandrum (Royle) Ying, a medicinal plant, has been endangered due to alpine habitat and overuse at Southeastern Tibet Plateau. This study aimed to examine the phenotypic traits and photosynthesis of S. hexandrum, including their relationship with main environmental factors, under low light (LL), moderate light (ML), and high light (HL) regimes. Low specific leaf mass was observed under LL, but the stomatal density and apparent quantum yield were the highest under this regime. The phenotypic traits, except for stomatal density and net photosynthetic rate, were the most notable under ML. The leaf area, stomatal density, apparent quantum yield, dark respiration, and stomatal conductance showed the smallest values under HL. Air temperature, photosynthetically active radiation, and air vapour pressure deficit significantly affected the stomatal characteristics and photosynthesis of S. hexandrum individuals. Our results suggested that a moderately shaded habitat could promote leaf development and the photosynthetic ability of S. hexandrum. [ABSTRACT FROM AUTHOR]

There is a trade-off between leaf structures and photosynthesis physiology. While numerous reports have shown a difference in photosynthesis between Gossypium hirsutum L. (upland cotton) and G. barbadense L. (pima cotton), the potential contribution of leaf structures on this difference was not fully clarified. Here, we investigated the differences in area- and mass-based photosynthetic traits and leaf structures between upland and pima cottons. Our results showed that upland cotton had higher area-based net photosynthetic rate (Parea) than that of pima cotton, which was attributed to the coordination of stomatal conductance (gs), area-based mesophyll conductance (gm-area), and maximum carboxylation rate (Vcmax-area). Parea, gm-area, and Vcmax-area correlated positively with leaf mass per area. But upland and pima cotton had similar mass-based PN (Pmass), gm (gm-mass), Vcmax (Vcmax-mass), suggesting that they have a similar photosynthetic capacity of single cells. Consequently, the higher area-based values in upland cotton were only due to a higher leaf thickness (Tleaf). [ABSTRACT FROM AUTHOR]

The effects of different concentrations of ferulic acid, chlorogenic acid, and protocatechuic acid were studied in a pot experiment to assess the response of Rhododendron delavayi seedlings. The results showed that three kinds of phenols promoted increases in chlorophyll (Chl) a, Chl b, total Chl, and carotenoid contents, but inhibited the accumulation of biomass. Low concentrations of ferulic acid significantly inhibited stomatal opening, the stomatal opening ratio, stomatal length and width. Chlorogenic acid and the moderate and high concentrations of ferulic acid also significantly inhibited stomatal density. Ferulic acid significantly inhibited net photosynthetic rate and stomatal conductance in seedlings, whereas chlorogenic acid significantly inhibited stomatal conductance. The low and moderate concentrations of chlorogenic acid significantly inhibited transpiration rate, and high concentrations of ferulic acid significantly inhibited the stomatal limitation value. The moderate concentration of protocatechuic acid significantly inhibited net photosynthetic rate and stomatal conductance. Ferulic acid exhibited a greater toxic effect than that of chlorogenic acid and protocatechuic acid for R. delavayi seedlings. [ABSTRACT FROM AUTHOR]

Photosynthesis is sensitive to water deficit (WD) stress. Maize (Zea mays L.) yield is vulnerable to water stress, especially if it occurs during the reproductive stage. In this study, the expression patterns of photosynthesis-related genes, together with photosynthetic gas-exchange and fluorescence parameters were investigated in a maize inbred line exposed to 50% of field water capacity (moderate WD) for 15 d after tassel emergence. The results demonstrated that WD down-regulated expression of psbA, psbB, psbC, psbP, psaA, psaB, and cab, especially at later periods of WD stress. Besides, with the increased WD stress, the steady decline in the value of photosynthesis performance index, maximum quantum yield of primary photochemistry, quantum yield for electron transport, quantum yield for the reduction of end acceptors of PSI per photon absorbed, and the efficiency of an electron beyond QA - that reduced PSI acceptors, and a clear increase in the J-step and I-step, K-band as well as L-band were observed. The results suggested that WD might restrict light-harvesting and electron transport. Interestingly, leaf transcript levels of rbcL and rbcS were up-regulated at the later stage of water stress in maize inbred line, which helped repair injury to PSII centers and maintain PSII activity (increased quantum yield of dissipation and effective antenna size of an active reaction center) under 15-d lasting WD. [ABSTRACT FROM AUTHOR]

In order to explore whether leaf area of developing leaves was regulated by systemic irradiance signal from mature leaves, we investigated the leaf area, leaf anatomy, photosynthesis, auxin, gibberellin, and cytokinin contents of new developing leaves in soybean growing under conditions of shaded mature leaves (MS), shaded whole plants (WS), and under full sunlight (NS). The results showed that developing leaves under MS exhibited the higher leaf area and leaf mass than that of WS. Blade thickness, palisade tissue thickness, sponge tissue thickness, cell size, cell numbers, net photosynthetic rate, stomatal conductance, transpiration rate, and cytokinin content of developing leaves under MS were lower, while auxin and gibberellin contents were higher than that of NS. These results indicate that the leaf area, leaf anatomy, and photosynthesis of developing leaves were regulated by the shading environment of mature leaves. Growth hormones may possibly act as candidate signal substances to systemic regulation of leaf area development. [ABSTRACT FROM AUTHOR]

Leaf gas exchange and growth responses of three melon cultivars, i.e., Mission, Da Vinci (var. reticulatus), and Super Nectar (var. inodorus) to two irrigation regimes, 50 and 100% crop evapotranspiration (ETc) were investigated under water-limited conditions of southwest Texas. In 2012, deficit irrigation (50% ETc) significantly decreased above-ground biomass, leaf area, leaf number, and specific leaf area, while leaf gas exchange, relative water content, water potential, chlorophyll fluorescence (Fv/Fm), and chlorophyll content (SPAD index) were not affected. However, in the drier year 2011, deficit irrigation significantly reduced net photosynthetic rate (PN) and stomatal conductance (gs). Further, the responses to water deficit varied with cultivars. At 50% ETc, PN and gs were maintained in cv. Da Vinci while decreased in Mission and Super Nectar. Thus, the late maturing cv. Super Nectar appeared to be more sensitive to drought stress, possibly due to the decrease in leaf area and PN. [ABSTRACT FROM AUTHOR]

Climate models predict an increase in atmospheric CO2 concentration and prolonged droughts in some parts of the Amazon, but the effect of elevated CO2 is still unknown. Two experiments (ambient CO2 400 ppm and elevated CO2 ? 700 ppm) were conducted to assess the effect of drought (soil at 50% field capacity) on physiological parameters of Carapa. At ambient CO2 concentration, light-saturated net photosynthetic rate (PNsat) was reduced by 33.5% and stomatal conductance (gs) by 46.4% under drought, but the effect of drought on PNsat and gs was nullified at elevated CO2. Total plant biomass and leaf area production were also reduced (42?47%) by drought. By changing leaf traits, Carapa is able to endure drought, as the consumptive use of water was reduced under drought (32?40%). The improvement of PNsat under elevated CO2 and water stress and the leaf plasticity of Carapa broaden our understanding of the physiology of Amazonian trees. [ABSTRACT FROM AUTHOR]