[Effects of sub-low temperature and drought stress on water transport and morphological anatomy of tomato plant].

We explored the effects of sub-low temperature and drought on water transport in tomato seedlings under normal temperature (25 ℃ day/18 ℃ night) and sub-low temperature (15 ℃ day/8 ℃ night) within the artificial climate chamber, and under normal irrigation (75%-85% field water holding capacity) and drought treatment (55%-65% field water holding capacity). We analyzed the effects of temperature and soil moisture on water transport, stomata and xylem vessel morpholo-gical and anatomical structure of tomato plants. The results showed that compared with condition of normal temperature + normal irrigation, drought treatment significantly reduced leaf water potential, transpiration rate, stomatal conductance, hydraulic conductance, sap flow rate, stomatal length, and diameter of leaf, stem and root conduit, and thus thickened the cell wall and enhanced the anti-embolism ability of conduit in leaf, stem and root. Leaf water potential, transpiration rate, stomatal conductance, hydraulic conductance, and conduit diameter in leaf, stem and root were significantly reduced by sub-low temperature treatment, but the stomata became larger, cell wall was thickened and the anti-embolism ability was enhanced in leaf, stem and root conduit. Under sub-low temperature condition, soil moisture did not affect leaf water potential, transpiration rate, stomatal conductance, hydraulic conductance, stomatal morphology, conduit structure of leaf and root. In conclusion, under drought treatment, the homeostasis in water relationship was obtained by the coordination of leaf, stem and root structure. Under sub-low temperature treatment, the regulation of water relationship was mainly dependent on the changes of conduit structure in leaf and root, which was less affected by soil moisture.