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Photosynthesis is sensitive to water deficit (WD) stress. Maize (Zea mays L.) yield is vulnerable to water stress, especially if it occurs during the reproductive stage. In this study, the expression patterns of photosynthesis-related genes, together with photosynthetic gas-exchange and fluorescence parameters were investigated in a maize inbred line exposed to 50% of field water capacity (moderate WD) for 15 d after tassel emergence. The results demonstrated that WD down-regulated expression of psbA, psbB, psbC, psbP, psaA, psaB, and cab, especially at later periods of WD stress. Besides, with the increased WD stress, the steady decline in the value of photosynthesis performance index, maximum quantum yield of primary photochemistry, quantum yield for electron transport, quantum yield for the reduction of end acceptors of PSI per photon absorbed, and the efficiency of an electron beyond QA - that reduced PSI acceptors, and a clear increase in the J-step and I-step, K-band as well as L-band were observed. The results suggested that WD might restrict light-harvesting and electron transport. Interestingly, leaf transcript levels of rbcL and rbcS were up-regulated at the later stage of water stress in maize inbred line, which helped repair injury to PSII centers and maintain PSII activity (increased quantum yield of dissipation and effective antenna size of an active reaction center) under 15-d lasting WD. [ABSTRACT FROM AUTHOR]

Chlorophyll (Chl) is generally positively related to corn grain yields; however, light-leaf-colored maize may also achieve high yields. Thus, Chl is seemingly not a key parameter for maize producers. Modern maize cultivars (55) were divided into four types, based on grain yields and ear leaf SPAD readings. The results revealed that there was no correlation between the SPAD readings and corn grain yields across different maize cultivars. High-yield maize possessed higher nitrogen, phosphorus, and potassium accumulation and utilization compared to that of low-yield maize; the N-transport efficiency of low yield and high SPAD was the lowest among various types of maize. Under normal conditions, parameters determining the high yield of maize in a sequence was leaf dry mass, Chl fluorescence indices, and light absorption flux per leaf cross section. A higher absorption flux, accompanied by high energy dissipation ratios, reduced the difference of trapped transport flux between high-SPAD and low-SPAD maize at high yield levels. At the low yield level, a higher absorption flux per reaction center compensated for the loss of PSII reaction center numbers in low-SPAD maize. [ABSTRACT FROM AUTHOR]