Stomatal conductance of tomato leaves is regulated by both abscisic acid and leaf water potential under combined water and salt stress
2021
Xue, Fulan | Liu, Weilu | Cao, Heli | Song, Lijin | Ji, Shasha | Tong, Ling | Ding, Risheng
Stomatal conductance (gₛ) affects water use efficiency (WUE) through coordinating photosynthesis and transpiration and is regulated by chemical and/or hydraulic signals. However, the regulation mechanism of gₛ of tomato leaves has not been fully explored under combined water and salt stress. Here, we set up four salt treatments and two water treatments in a climate greenhouse and measured stomatal morphologies and conductance and other photosynthesis parameters. Water and salt stress reduced stomatal length (SL), width, perimeter, area (aₘₐₓ), density (SD), and the maximum stomatal conductance (gₛₘₐₓ). Water and salt stress had a separate weakening effect on net photosynthetic rate (A) and transpiration rate but interactively reduced gₛ. The contents of abscisic acid (ABA) and Na⁺ in tomato leaves increased with the NaCl concentration, while leaf water potential (Ψₗ) and chlorophyll content decreased. Under full irrigation, gₛₘₐₓ was coordinated by SD and aₘₐₓ, and gₛ by ABA content under salt stress. Under water and salt combined stress, gₛₘₐₓ was affected by aₘₐₓ, and gₛ was coordinated with ABA and Ψₗ. The decrease of A was caused by both a reduction of chlorophyll content and gₛ under water and salt stress. Intrinsic WUE did not reduce under full irrigation or mild to moderate salt stress but decreased under a combination of water and severe salt stress, indicating that the leaves of the tested tomato cultivar performed better under moderate salt stress. Collectively, these results can provide useful insights for the efficient management of water and salt to adapt to drought and high salt environments.
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