Response of chlorophyll synthesis and fluorescence characteristics of oat seedlings to soil drought

Soil drought is one of the important factors that restricts the growth and development of oat (Avena sativa) seedlings in the Qinghai Province of China. To clarify the response mechanism of oats to drought, oat variety ‘Qingyan No. 1’ widely cultivated in Qinghai, China, was selected as a test material using a single factor random block design, with four water treatments and field capacity of 75%, 60%, 45%, and 30%. The purpose of this study was to explore the response characteristics of chlorophyll, precursors, and fluorescence parameters of oat seedlings to drought stress, improve the deficiency of oat variety during drought, and provide a theoretical basis for the evaluation of drought resistance of oats. The results showed that different soil droughts had significant effects on the growth and development of oat seedlings. Compared with the control, the height of seedling decreased by 24.3%～57.4%, the ratio of leaf length to leaf width decreased by 44.0%～68.2%, the ratio of root to shoot increased 90.3%～129.0%. Drought led to metabolic imbalance of chlorophyll and its precursors, mainly characterized by an increase in the content of δ-aminolevulinic acid and a decrease in the contents of PBG, Cop Ⅸ, Proto Ⅸ, Mg-Proto Ⅸ, and Pchl, consequently resulting in a decrease in chlorophyll content. The reduced chlorophyll caused the imbalance in light energy absorption, utilization, and distribution in the photosynthetic system of oats. Excess light energy was lost mainly in the form of heat dissipation, which may be an important strategy for oats in protecting the photosynthetic system from photoinhibition and light damage.