The Role of Active and Passive Water Uptake in Maintaining Leaf Water Status and Photosynthesis in Tomato under Water Deficit

概要

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Tomato(Lycopersicon esculentum Mill.cv.Know-You 301)shoots were grafted onto the rootstock of the same species or Salanum mammosum and grown in nutrient solution. After the grafted tomato plants developed 4-5 leaves, the uppermost fully expanded leaves were used to determine net photosynthetic rate(P_N), transpiration rate and leaf water potential(Ψ_L)under control(unstressed)and -0.5 MPa water deficit(mannitol was added to nutrient solution). Both PN and leaf conductance(G_L)were reduced under water deficit. However, tomato plants grafted onto S.mammosum rootstock had higher Ψ_L, P_N and G_L than those grafted onto tomato rootstock under water deficit. This result demonstrates that S.mammosum roots had a greater ability in water uptake under water deficit. Under +0.2 MPa pressure, the root of S.mammosum showed a higher exudation rate than that of tomato. However, the former showed a lower exudation rate than the latter under -0.5 MPa water deficit. It was concluded that the greater ability of water uptake in S.mammosum rootstock under water deficit is related to a lower hydraulic conductivity, which promotes passive, rather than active water uptake.
日本作物学会の論文