Effects of exogenous melatonin on physiological and photosynthetic characteristics of wheat seedings

Abstract

To explore the effects of different concentrations of melatonin on physiological and photosynthetic fluorescence characteristics of wheat seedlings. The growth morphology, photosynthetic, fluorescence parameters and antioxidant enzyme activity of wheat seedings treated with different concentrations of melatonin were determined by using Liangxing 99 as experimental material. The results were as follows: (1) 0.1 μmol·L-1 melatonin treatment significantly increased the photosynthetic capacity of wheat plants, Chlorophyll a (Chl a), Chlorophyll b (Chl b) and Chlorophyll (a+b)［Chl (a+b)］increased to the maximum value when melatonin concentration was 0.1 μmol·L-1. Chlorophyll fluorescence parameters include parameters of quantum yield of regulated energy dissipation Y (NPQ), the electron transport rate (ETR) and non-photochemical quenching (NPQ) also reached the maximum at 0.1 μmol·L-1. The PS Ⅱ maximum photosynthetic efficiency (Fv/Fm) and maximum photochemical conversion potential (Fv/Fo) decreased with the increase of melatonin concentration. Photochemical quenching (qL) decreased first and then increased with the increase of melatonin. (2) Compared with CK (0 μmol·L-1), low concentration of melatonin treatment significantly decreased peroxidase (POD) activity in wheat and decreased catalase (CAT) activity in wheat leaves, high melatonin concentration significantly increased POD activity in wheat. The content of malondialdehyde (MDA) in wheat roots decreased firstly and then increased with the increase of melatonin concentration. In conclusion, it suggests that appropriate melatonin treatment can promote the growth of wheat and maintain the photosynthetic capacity of wheat at a high level, and can also regulate oxidative stress induced by different concentrations of melatonin in wheat seedlings through POD and CAT. This study laid a foundation for further understanding the regulatory mechanism of melatonin in wheat.

Keywords

• melatonin
• wheat
• chlorophyll
• chlorophyll fluorescence
• photosynthetic characteristics
• physiology