Grain sorghum [Sorghum bicolor (L.) Moench. cvs. TX430 and KS82] was grown in a Haynie very fine sandy loam (coarse-silty, mixed, superactive, calcareous, mesic Mollic Udifluvents) under constant 47 % shade or full irradiance in a greenhouse under two watering regimes to see the combined and individual effects of low irradiance (LI) and low water (LW) on the sorghum genotypes. Under the high-irradiance (HI) and high-water (HW) treatment (control) and the LI-HW treatment, TX430 grew taller than KS82. Both LI and LW reduced several times the fresh and dry masses. Under the control conditions, TX430 reached its maximum net photosynthetic rate (PNmax) of 28.93 μmol m-2 s-1 at a photosynthetic photon flux density (PPFD) of 1 707 μmol m-2 s-1, and KS82 reached its PNmax of 28.32 μmol m-2 s-1 at a PPFD of 2 973 μmol m-2 s-1. The fact that TX430 had PNmax under a lower PPFD than KS82 may relate to its taller growth under LI conditions. Hence genotypes of sorghum might be selected for low irradiance using curves relating PN to PPFD. and Qingzhang Xu, M. B. Kirkham.
Drought significantly constrains higher yield of alfalfa (Medicago sativa L.) in arid and semiarid areas all over the world. This study evaluated the responses of leaf cuticular wax constituents to drought treatment and their relations to gas-exchange indexes across six alfalfa cultivars widely grown in China. Water deficit was imposed by withholding water for 12 d during branching stage. Cuticular waxes on alfalfa leaves were dominated by primary alcohols (41.7-54.2%), alkanes (13.2-26.9%) and terpenes (17.5-28.9%), with small amount of aldehydes (1.4-3.4%) and unknown constituents (4.5-18.4%). Compared to total wax contents, the wax constituents were more sensitive to drought treatment. Drought decreased the contents of primary alcohol and increased alkanes in all cultivars. Alkane homologs, C25, C27, and C29, were all negatively correlated with photosynthetic rate, transpiration rate, stomatal conductance, and leaf water potential. Under drought conditions, both stomatal and nonstomatal factors were involved in controlling water loss from alfalfa leaves. No direct relationship was observed between wax contents and drought resistance among alfalfa cultivars. An increase in alkane content might be more important in improving drought tolerance of alfalfa under water deficit, which might be used as an index for selecting and breeding drought resistant cultivars of alfalfa., Y. Ni ... [et al.]., and Obsahuje bibliografii
Xerophytic stomatal traits may help plants maintain photosynthetic rates under water deficit; however, such adaptations are not well understood. A pot experiment was conducted with two winter wheat cultivars (Pubing 143, Zhengyin 1) during the grain-filling period. Net photosynthetic rate (PN) and chlorophyll (Chl) content were significantly less affected by water deficit in Pubing 143 than that in Zhengyin 1, and the variation in both PN and Chl content were more stable in spikes compared to flag leaves. At 18 days after anthesis, stomatal conductance of spikes in Pubing 143 were 28% lower than that of the control, while transpiration rate was 34% lower in Zhengyin 1 under water deficit. We provided the first evidence of amphistomatous stomata on the lemma of winter wheat spikes through scanning electron microscopic observations. The finding of the amphistomatous stomata is an important contribution to stomatal distribution and may help explain how wheat spikes can maintain high photosynthetic rates even under drought conditions., H. Ding, D. Liu, X. Liu, Y. Li, J. Kang, J. Lv, G. Wang., and Obsahuje bibliografii