Alterations in leaf photosynthetic electron transport in Welsh onion (Allium fistulosumL.) under different light intensity and soil water conditions

Welsh onions (Allium fistulosumL.) are often affected by stressful environments, such as high light and drought, during summer cultivation, which hinders their growth. We used CO(2)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.F(O)andF(J)increased,F(m)decreased, and a distinct K-phase was induced. High light and drought stress blocked MR transients, leading to a gradual decrease in V(PSI)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.

Automated summary

The research found that high light and drought have different effects on the photosynthesis of Welsh onions. High light causes stomatal limitation leading to a decrease in the net photosynthesis rate, while drought and high light combined lead to non-stomatal limitation. Both conditions result in the damage to the receptor and donor sides of PSII, reducing the photosynthetic efficiency of Welsh onions.