Effects of nitrogen fertilization on chlorophyll fluorescence change in maize (Zea mays L.) under waterlogging at seedling stage.

摘要

The effects of four different nitrogen (N) fertilizer application protocols on maize under waterlogging stress at seedling stage was investigated through chlorophyll (Chl) fluorescence parameters, photosynthetic pigment contents, leaf area index (LAI), and rapid light curve (RLC). The results showed that waterlogging stress decreased the maximal efficiency of PSII photochemistry (Fv/Fm) in dark-adapted leaves. Moreover, the contents of Chl and Chla/b, LAI, the actual PSII efficiency ( Phi _PSII), photochemical quenching coefficient (qP), and the fraction of light used in PSII photochemistry (P%) also dropped under waterlogging stress, but non-photochemical quenching (NPQ), thermal energy dissipation (D%) and excess of energy excitation (X%) showed different response which increased under waterlogging stress. As to different N fertilization, postponed N supply could improve photosynthetic capacity by increasing LAI and Chl contents, and alleviating the photosynthetic efficiency decreased under waterlogging stress. From the chlorophyll fluorescence rapid light curves, the results showed that compared with control, waterlogging stress at seedling stage significantly decreased the maximal relative electron transport rate (ETRmax), initial slope ( alpha ), and half saturation point of light intensity (E_k). Postponed N fertilizer application alleviated the photodamage to PSII caused by waterlogging stress, and the compensation effect of late N fertilization occurred earlier than that of early N fertilization. Photosynthetic characters of maize under waterlogging stress at seedling stage exhibited positive responses to N supply which indicates that postponed N fertilizer supply is recommended to improve photosynthetic efficiency and alleviate photodamage under waterlogging stress at seedling stage.