Salinity Down-Regulates Transpiration Rate of Medicago sativa to Increasing Vapour Pressure Deficit
Hongbin Wei1, Marcus Giese1, Yingzhi Gao2, Qiushi Ning3, Folkard Asch1
1University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Germany
Medicago sativa is perennial forage with high yield and good quality. Plants growing in arid and semi-arid regions are often subjected to soil and atmospheric water deficit as well as high soil salinity during their life cycles. Plant transpiration increases at elevated atmospheric vapour pressure deficit (VPD), C3 species are reported to have a breakpoint (BP), above which stomatal conductance declines and limits transpiration rate to a maximum. Soil salinity is likely to be involved in transpiration response by affecting root hydraulic resistance, leaf water potential and stomatal conductance in salt-treated plants. The objective of this study was to compare the transpiration response of Medicago sativa over a range of VPD at various salt concentrations to identify the tolerance mechanisms to confront atmospheric water vapour deficit and salinity. Seeds of Medicago sativa were cultivated in a greenhouse till 8 weeks old and subjected to five salt treatments of 0, 40, 80, 120, 160 mM (NaCl :Na2SO4 = 1:1) for 14 days. Then plants were exposed to increasing VPD (0.5, 1.0, 1.5, 2.5, 3.5 kPa) in a controlled environment chamber.
Keywords: Medicago sativa, salinity stress, transpiration rate, vapour pressure deficit
Contact Address: Marcus Giese, University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Stuttgart, Germany, e-mail: m.gieseuni-hohenheim.de