遮荫对番茄单叶水分利用效率的影响研究

通过逐个分析3种遮荫水平下各参数变化对番茄单叶水分利用效率(WUE)的影响表明,各环境因子以综合复杂的方式影响水分利用效率,其中气孔阻力和水汽压差随环境因子变化最为重要。夏季晴天午间遮荫处理的气孔阻力和水汽压差明显小于对照,气孔阻力的增加有利于提高单叶水分利用效率,但水汽压差的增大又使单叶水分利用效率降低。由于环境因子日变化的非对称性和2种机制的相互作用,导致3种遮荫水平下单叶水分利用效率的日变化呈浅“L”型,并在12:00～15:00时40％遮荫处理的单叶水分利用效率比对照平均增加22.9％,而75％遮荫处理的单叶水分利用效率平均比对照显著减少28.1％,表明夏季晴天午间充足供水条件下适度遮荫可提高番茄单叶水分利用效率。

Effects of environmental factors under shading conditions on water use efficiency of tomato leaves

Effects of all parameters influenced by the three levels of shading (0% shading,HL; 75% shading,LL; 40% shading,ML) on water use efficiency (WUE) of tomato leaves grown in pots under well-watered conditions were investigated in summer sunny midday.The results show that environmental factors influence WUE synthetically and complexly,especially,stomatal resistance and vapor pressure difference (VPD).The stomatal resistance and the VPD increase by high evaporation potential because strong light and high temperature at noon at HL are more greater than those at ML and LL treatments.The increase in stomatal resistance can increase WUE,but the increase of VPD can decrease WUE.Daily variations of WUE under three shading levels show shallow "L" type,which are caused by the non-symmetry of diurnal variations of environmental factors and interaction of two mechanisms above.Compared with the non-shaded control,the average single leaf WUE of 40%-shaded plants increases by 22.9% during the 12:00~ 15:00 in summer sunny day,while the WUE for 75%-shaded plants reduces significantly by 28.1%,showing that moderate shading can enhance WUE of tomato leaves under sufficient water condition on summer midday.