Three ecotypes of reed (Phragmites communis Trinius), swamp reed (SR), dune reed (DR), and heavy salt meadow reed (HSMR), growing in desert regions of northwest China were simultaneously investigated in their natural state for gas exchange patterns and the expression of three photosynthesis-related genes, cab (the gene for the light-harvesting chlorophyll a/b binding protein, LHC), psbA (the gene for the reaction centre D1 protein of photosystem 2, PS2), and 16S rDNA (the gene for plastid 16S rRNA). Stomatal conductance (gs) and intercellular CO2 concentration (ci) were markedly lower in the two terrestrial ecotypes (DR and HSMR) as compared to SR, paralleling a similar observed depression in net photosynthetic rate (PN). However, DR with the lowest measured gs and ci still exhibited a higher PN compared to HSMR. These results suggest that both stomatal and non-stomatal factors account for the comparatively low carbon assimilation in the terrestrial ecotypes. An increase in the expression of photosynthesis-related genes was observed in DR compared to SR, whereas the reverse situation was true in HSMR. The expression of photosynthesis-related genes may contribute to reed plants' photosynthetic capacity per leaf area under natural water deficits, but the levels of photosynthesis-related gene expression are not directly correlated with reed plants' general ability for survival and adaptation under water deficient conditions. and H. L. Wang ... [et al.].
The influence of various concentrations of imazapic residues (0-800 μg kg-1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection., W. C. Su, L. L. Sun, R. H. Wu, Y. H. Ma, H. L. Wang, H. L. Xu, Z. L. Yan, C. T. Lu., and Obsahuje bibliografii