水盐胁迫对玉米茎木质部水力特性的影响

Change in Hydraulic Characteristics of Maize in Response to Water and Salinity Stresses

【目的】探讨水盐胁迫下玉米茎木质部水力特征、光合作用和生长指标的响应,深入探究水盐胁迫诱导茎木质部栓塞形成的机理。【方法】通过室内玉米桶栽试验,设置水分胁迫(LD)、盐分胁迫(WS)和水盐联合胁迫(SY)3个胁迫处理,以无水盐胁迫处理作为对照(CK),研究水盐胁迫对玉米叶、根水势及玉米茎木质部水力特性的影响。【结果】与CK相比,水盐胁迫下玉米根、叶水势均有明显降低,叶-土水势差从大到小的顺序依次为CK>LD处理>WS处理>SY处理;茎干的初始水力导度Ki和茎流速率明显降低,其变化趋势与叶-土系统水势差变化趋势一致,相应地茎木质部水力导度损失百分比PLC显著增大;同时,玉米叶片的净光合速率Pn、蒸腾速率Tr、气孔导度Gs呈CK>LD处理、WS处理>SY处理,株高和叶片长度均表现为CK>LD处理>WS处理>SY处理。【结论】水盐胁迫均会降低玉米水势,使植株体内渗透势平衡遭到破坏,导致玉米光合性能受到抑制,使茎木质部内产生空穴化和栓塞现象,且不同胁迫方式导致不同程度的栓塞。

【Objective】Drought and salinity are most common abiotic stresses impending crop growth,and understanding how crops hydraulically respond to these stresses is imperative for improving agronomic management.In this paper,we present the results of an experimental study on the impact of water and salinity stresses on water characteristics of maize.【Method】The experiment was conducted in a phytotron and consisted of four treatments:water stress(LD),salt stress(WS),coupled water and salt stress(SY);the control was without stress(CK).In each treatment,we measured leaf water potential,root water potential and stem hydraulic conductivity of the maize.【Result】Compared with CK,LD,WS and SY reduced water potential in both root and leaf noticeably.In all treatments,the difference between water potential in the leaf and the soil was in the order of CK>LD>WS>SY.Water and salinity stresses both reduced initial hydraulic conductivity and sap flow rate in a similar way as their impact on the difference between water potential in the leaf and the soil;they led to an increase in the percentage of hydraulic conductivity loss of the stem xylem(PLC).Water stress reduced net photosynthetic rate,transpiration rate and stomatal conductance,and coupling water and salt stresses reduced these traits further.Plant height and leaf length in all treatments was in the order CK>LD>WS>SY.【Conclusion】Water and salt stresses in separation or in coupling both reduced water potential and imbalanced osmotic potential in the plant,thereby inhibiting photosynthesis and embolizing the stem xylem network,although the embolization varied with types and degree of the stresses.