Abstract:

The study was carried out in the Experimental Station of Tieling, a normal irrigation (soil water content was about 75%) and a short-term drought-stress (soil water content was naturally reduced by 8 days, and re-watered to normal after wilting) at flowering-pegging stage of peanut were set up, with three nitrogen levels (0, 90, 180 kg/hm²), to explore the effect of nitrogen application on photosynthesis and fluorescence characteristics of peanut under drought, thus providing reference for nitrogen application at peanut flowering-pegging stage. The results showed that soil water content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO₂ concentration (Ci) were significantly reduced, but chlorophyll content of peanut was increased under drought-stress. Under drought-stress, Pn, Tr, Gs, Ci and chlorophyll content of 90 kg/hm² treatment were the best among the three levels of nitrogen application. Under drought-stress, the initial fluorescence of leaf (F₀) was significantly increased with the increase of nitrogen; the maximum photochemical efficiency of photosystemⅡ(Fv/Fm), the quantum efficiency of electron transport (ФPSⅡ), the electron transport rate (ETR) and the photochemical quenching co-efficient (qP) significantly declined, but the non-photochemical quenching co-efficient (NPQ) was significantly increased. Under drought-stress, Fv/Fm, ФPSⅡ, ETP and qP reached the highest level at 90 kg/hm² nitrogen application level. No application (0 kg/hm²) or excessive application (180 kg/hm²) of nitrogen fertilizer was not conducive to photosynthesis of peanut leaves. All results suggest that 90 kg/hm² is the optimal nitrogen level to improve photosynthesis and fluorescence characteristics of peanut, and achieve high yield.

Key words: flowering-pegging stage, peanut, drought, nitrogen, photosynthesis, fluorescent characteristics