In a field experiment, two winter wheat (Triticum aestivum L.) cultivars, Tainong 18 (a large-spike cultivar) and Jinan 17 (a multiple-spike cultivar), were treated with 78% (S1), 50% (S2), and 10% (S3) of full sunshine (S0, control) from anthesis to maturity to determine the responses of photosynthetic characteristics and antioxidative enzyme activities in a flag leaf. Compared with S0 treatment, the chlorophyll (Chl) content and maximal efficiency of photosystem II (PSII) photochemistry (Fv/Fm) of flag leaves were enhanced in treatments S1 and S2. From 0 to 7 d post flowering, the Chl content and Fv/Fm in S3 were also higher than those in S0, but significantly lower than those in controls, respectively. With the increase of shading intensity, the effective quantum yield of PSII (ΦPSII) was promoted; whereas, the ratio of Chl a/b declined. Compared with S0, treatments S2 and S3 significantly suppressed the activities of superoxide dismutase (SOD) and peroxidase (POD), net photosynthetic rate (PN), and contents of total soluble sugar, nevertheless, S1 treatment showed positive effects on the above parameters. Under the same shading condition, Jinan 17 had larger Chl content and higher activities of PSII and antioxidative enzymes, but lower malondialdehyde (MDA) content than Tainong 18. The results indicated that multiple-spike cultivar was more advantageous for the Huang-Huai-Hai Plain, where shading problem occurs later during the growth period, than the large-spike cultivar, because of the lesser damage in a flag leaf and better photosynthetic function of the former one. Wheat plants under S1 shading condition had relatively high activities of antioxidative enzymes and a low degree of membrane lipid peroxidation, which was in favor of stress resistance, maintaining high PN duration, and accumulation of photosynthates in wheat plants., C. Xu ... [et al.]., and Obsahuje bibliografii
As a common tree species in northern China, Populus × euramericana "Neva" has an important practical value for the study of continuous cropping obstacles in poplar cultivation. Plant allelopathy is the main reason for continuous cropping obstacles, which are caused by allelochemicals, such as para-hydroxybenzoic acid (p-HB). The objective of this study was to investigate the effects of p-HB on the photosynthesis of poplar. Photosynthetic parameters of Populus × euramericana "Neva" poplar were determined in a pot culture experiment where five p-HB concentrations were used (0, 1, 2, 4, and 6 mmol L−1). Each seedling was treated with 4 L of p-HB solution every seven days, ten times in total. p-HB inhibited the photosynthesis of poplar significantly, as shown by a clear decline in the net photosynthetic rate. Our results indicated nonstomatal limitation responsible for the photosynthesis reduction., G. T. Liang, S. Y. Zhang, J. Guo, R. Yang, H. Li, X. C. Fang, G. C. Zhang., and Obsahuje bibliografii