Effects of shading on photosynthetic characteristics of different genotype maize

A pot experiment with 4 genotype maize varieties showed that light intensity had strong effects on their leaf light saturation point, diurnal variation of net photosynthetic rate (Pn), estimated electron transport rate (ETR), maximal photochemical efficiency of PS II (Fv/Fm), and actual photochemical efficiency of PSII (Phi(PS II)). Under shading, the light saturation point of test varieties decreased. For example, shading at seedling stage made the varieties Yuyu 2 and Danyu 13 get to light-saturated when the photon flux density (PFD) was 1400 micromol.m(-2).s(-1) and 1100 micromol.m(-2).s(-1), respectively. Shading also decreased the Pn, ETR, Fv/Fm and Phi(PS II), but the responses differed with the varieties. The decrement of these parameters was remarkably lesser for Yuyu 2 and Yedan 22 than for Danyu 13 and Yedan 6.