Diurnal variation of gas exchange, chlorophyll fluorescence, and xanthophyll cycle components of maize hybrids released in different years |
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Authors: | L Ding K J Wang G M Jiang Y G Li C D Jiang M Z Liu S L Niu Y Peng |
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Institution: | (1) Laboratory of Quantitative Vegetation Ecology, Institute of Botany, the Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, 100093 Beijing, P.R. China;(2) Agronomy Department, Shandong Agriculture University, 271018 Tai'an, P.R. China |
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Abstract: | Diurnal variation of gas exchange, chlorophyll (Chl) fluorescence, and xanthophyll cycle components of three maize (Zea mays L.) hybrids released in different years, i.e. Baimaya (1950s), Zhongdan2 (1970s), and Nongda108 (1990s), were compared. On cloudless days, the newer hybrids always had
higher net photosynthetic rate (P
N), especially at noon, than the older ones. At noon, all the hybrids decreased their maximal yield of photosystem 2 (PS2)
photochemistry (Fv/Fm) and actual quantum yield of PS2 (ΦPS2), the newer ones always showing higher values. Generally, the newer hybrids displayed higher photochemical quenching of Chl
(qP) and lower non-photochemical quenching (NPQ). The interhybrid differences in P
N may be owing to their differential photochemical efficiency. A midday depression in P
N occurred in all hybrids, which might be caused by serious photoinhibition or by decreased stomatal conductance. However,
midday depression in P
N was more obvious in the older hybrids, especially when leaves were senescent. The higher de-epoxidation state of the xanthophylls
was noted in older hybrids, which was confirmed by their larger NPQ. The newer maize hybrids did not need a strong de-epoxidation
state since they had a better photosynthetic quantum conversion rate and a lower NPQ. |
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Keywords: | fluorescence quenching parameters intercellular CO2 concentration net photosynthetic rate stomatal conductance Zea mays |
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