Abstract
Welsh onions (Allium fistulosum L.) are often affected by stressful environments, such as high light and drought, during summer cultivation, which hinders their growth. We used CO2 assimilation, OJIP transient and MR curves to analyse the photosynthetic characteristics of Welsh onion. The results showed that single high light stress caused a decrease in the net photosynthesis rate through stomatal limitation, while the single drought treatment and the combined stress induced nonstomatal limitation. FO and FJ increased, Fm decreased, and a distinct K-phase was induced. High light and drought stress blocked MR transients, leading to a gradual decrease in VPSI and VPSII-PSI . In general, photosynthesis of Welsh onion was inhibited by high light and drought, which destroyed the receptor and donor side of PSII and reduced electron transport capacity of PSII and PSI.
Highlights
Welsh onions are often affected by stressful environments, such as high light and drought, during summer cultivation, which hinders their growth
In general, the photosynthesis of Welsh onion was inhibited by high light and drought, which destroyed the receptor and donor side of Photosystem II (PSII) and reduced the electron transport capacity of PSII and Photosystem I (PSI)
We aimed to study the resistance of Welsh onion leaves under drought and high light conditions by examining photosynthetic parameters, focusing on the interaction between PSII and PSI using carbon dioxide assimilation, the OJIP curve and the modulated nm reflection (MR) curve
Summary
Welsh onions are often affected by stressful environments, such as high light and drought, during summer cultivation, which hinders their growth. In the summer in northern China, a combination of high irradiance, high temperature and water stress (i.e., drought) is very common[1]. These limiting factors usually last a long time in the summer, which seriously affects plant growth and survival. When exposed to both drought and high light, plants respond with defensive reactions that involve more efficient water use, maintain high carbon dioxide assimilation with few stomatal openings, and initiate several photoprotective measures [2, 3]. The two photosystems [Photosystem I (PSI) and Photosystem II (PSII)] are vulnerable to damage during photosynthesis [4, 5]
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