The effects of selenium on photosynthesis and Chl fluorescence in pear, grape, and peach were analyzed. The foliar spray of amino acid-chelated selenium solution was performed soon after fruit setting, totally six times, with an interval of ten days. After seven days from the last spray, the leaves in the middle of shoots were examined. Foliar spray of selenium increased the net photosynthetic rate in pear, grape, and peach. In contrast, the treatment decreased stomatal conductance, transpiration rate, and substomatal CO2 concentration in all the three species. The selenium treatment improved the maximum quantum yield of PSII, effective quantum yield of PSII, and photochemical quenching in all three species. Conversely, the selenium treatment reduced nonphotochemical quenching in all three species. We suggested that selenium can improve photosynthesis and protect PSII in fruit crops., T. Feng, S. S. Chen, D. Q. Gao, G. Q. Liu, H. X. Bai, A. Li, L. X. Peng, Z. Y. Ren., and Obsahuje seznam literatury
The ratío between carotenoid and chlorophyll a concentrations (Car/Chla) is indicative of the physiology and phenology of plants. With the aim of assessing this Car/Chla pigment ratio from reflectance (R), a wide range of leaves from several species and conditions were measured with high spectral resolution spectroradiometers for X between 400 and 800 nm. The performances of three pigment reflectance indices; (7) simple ratio pigment index (SRPI = R^*/R^2), (2) normalized difference pigment index [NDPI = (R^’ - R^^y^^RXi + R^2)]^ g^d (i) the structure insensitive pigment index [SIPI = (R**^ - R^i)/(R®*^ - R^^)] were tested. For each pigment index, every set of wavebands [Aj, X'^ was systematically tested. High correlations with Car/Chla were found for all these pigment indices in the blue-red domain [400 nm<A,i<530 nm, 600 nm<A,2<700 nm] as expected since both Chl and Car absorb in the blue, while only Chl absorbs in the red. The best semi-empirical estimation of the Car/Chla ratio was provided by SIPI for the wavelengths 445 and 680 nm: Car/Chla = 4.44 - 6.77 exp[-0.48 (R^oo. r445)/(r800 . R680)j| This index minimizes the confounding effects of leaf surface and mesophyll structure. These reflectance pigment indices provide new insight in the use of remote sensing for the assessment of physiology and phenology of vegetation.