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Many studies have been conducted on maize to study the effect of drought on yield at the flowering stage, but understanding biochemical and photosynthetic response against drought at the seedling stage needs to be well established. Thus, to understand differential changes and interaction of biochemical and photosynthetic parameters at the seedling stage under drought, a greenhouse experiment with twelve maize genotypes under severe drought (30% field capacity) and irrigated (90-100% field capacity) conditions were performed. Drought differentially altered biochemical and photosynthetic parameters in all genotypes. A sharp increase in hydrogen peroxide, malondialdehyde (MDA), and total antioxidant capacity (TAOC) were seen and a positive association between H2O2 and TAOC, and MDA and transpiration rate (E) was observed under drought. Nonphotochemical quenching increased under drought to avoid the photosystem damage. PCA biplot analysis showed that reducing E and increasing photosynthetic efficiency would be a better drought adaptation mechanism in maize at the seedling stage. [ABSTRACT FROM AUTHOR]

We selected the elite clone of Pinus sylvestris var. mongolica 'GS1' from 365 clones in a primary seed orchard in Liaoning Province, China. To understand the photosynthesis characteristics and mechanisms, 40-year-old 'GS1' trees were compared with a common clone 'H524' of the same age at the same seed orchard. Results showed that 'GS1' had higher net photosynthetic rate because of higher stomatal conductance (gs); the larger external and inner diameters of stomata were the structural factors enabling maintenance of higher gs. The higher light-saturated net photosynthetic rate of 'GS1' was mainly due to higher electron transfer activity, demonstrated by the lower relative fluorescence intensity from O-step to P-step. The increase in density of active reaction centers resulted in an increase in energy flux per cross section, which led to higher photosynthetic performance. [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]

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]