Effects of exogenous melatonin on growth and photosynthesis of maize (Zea mays L.) seedlings under low nitrogen stress

Abstract

Nitrogen plays an important role in plant growth and development. Melatonin (Mel) is involved in many physiological and biochemical reactions in plants, which can enhance the resistance of plants to abiotic stress. However, the mechanism of exogenous Mel in maize seedlings under low nitrogen stress is still unknown. This experiment adopts the method of sand culture, Zhengdan 958 was used as the experimental variety, and three nitrogen levels (5mmolL⁻¹, 2mmolL⁻¹, 0.1mmolL⁻¹) and two Mel treatment conditions (no exogenous Mel and 1μmolL-1 exogenous Mel) were set up to explore the effects of exogenous Mel on the growth and photosynthesis of maize seedlings under low nitrogen stress. The growth of maize seedlings under low nitrogen stress was significantly inhibited. Exogenous melatonin (Mel) increased the shoot dry weight by 11.74 % and 17.57 % under mild and severe low nitrogen stress, respectively. It promoted root growth, enhanced nitrogen accumulation in the shoots, and improved the net photosynthetic rate of maize seedlings, with increases of 14.85 % and 24.77 % under mild and severe low nitrogen stress, respectively.Exogenous Mel improved the activity of the reaction centers in photosystem I (PSI) and photosystem II (PSII), increased electron transport rates, thereby enhancing light energy conversion efficiency and allocating more light energy to photochemical reactions. Additionally, exogenous Mel effectively alleviated the photo-oxidative damage to the photosynthetic systems caused by low nitrogen stress. This study demonstrated that exogenous Mel could significantly mitigate the inhibitory effects of low nitrogen stress on maize seedling growth.