Bahrun Andi, Jensen Christian R, Asch Folkard, Mogensen Vagn O
The Royal Veterinary and Agricultural University, Department of Agricultural Sciences, Laboratory for Agrohydrology and Bioclimatology, Agrovej 10, DK-2630 Taastrup, Denmark.
J Exp Bot. 2002 Feb;53(367):251-63. doi: 10.1093/jexbot/53.367.251.
Early signals potentially regulating leaf growth and stomatal aperture in field-grown maize (Zea mays L.) subjected to drought were investigated. Plants grown in a field lysimeter on two soil types were subjected to progressive drought during vegetative growth. Leaf ABA content, water status, extension rate, conductance, photosynthesis, nitrogen content, and xylem sap composition were measured daily. Maize responded similarly to progressive drought on both soil types. Effects on loam were less pronounced than on sand. Relative to fully-watered controls, xylem pH increased by about 0.2 units one day after withholding irrigation (DAWI) and conductivity decreased by about 0.25 mS cm(-1) 1-3 DAWI. Xylem nitrate, ammonium, and phosphate concentrations decreased by about 50% at 1-5 DAWI and potassium concentration decreased by about 50% at 7-8 DAWI. Xylem ABA concentration consistently increased by 45-70 pmol ml(-1) at 7 DAWI. Leaf extension rate decreased 5 DAWI, after the changes in xylem chemical composition had occurred. Leaf nitrogen significantly decreased 8-16 DAWI in droughted plants. Midday leaf water potential and photosynthesis were significantly decreased in droughted plants late in the drying period. Xylem nitrate concentration was the only ionic xylem sap component significantly correlated to increasing soil moisture deficit and decreasing leaf nitrogen concentration. Predawn leaf ABA content in droughted plants increased by 100-200 ng g(-1) dry weight at 7 DAWI coinciding with a decrease in stomatal conductance before any significant decrease in midday leaf water potential was observed. Based on the observed sequence, a chain of signal events is suggested eventually leading to stomatal closure and leaf surface reduction through interactive effects of reduced nitrogen supply and plant growth regulators under drought.
对田间种植的玉米（Zea mays L.）在干旱条件下可能调节叶片生长和气孔开度的早期信号进行了研究。在两种土壤类型的田间蒸渗仪中生长的植株，在营养生长阶段遭受渐进性干旱。每天测量叶片脱落酸含量、水分状况、伸长率、导度、光合作用、氮含量和木质部汁液成分。两种土壤类型上的玉米对渐进性干旱的反应相似。对壤土的影响比对砂土的影响不那么明显。相对于充分浇水的对照，停止灌溉（DAWI）一天后木质部pH值增加约0.2个单位，1 - 3天DAWI时电导率降低约0.25 mS cm(-1)。1 - 5天DAWI时木质部硝酸盐、铵和磷酸盐浓度降低约50%，7 - 8天DAWI时钾浓度降低约50%。7天DAWI时木质部脱落酸浓度持续增加45 - 70 pmol ml(-1)。木质部化学成分发生变化后，叶片伸长率在5天DAWI时下降。干旱植株中叶片氮含量在8 - 16天DAWI时显著降低。在干旱后期，干旱植株的午间叶片水势和光合作用显著降低。木质部硝酸盐浓度是唯一与土壤水分亏缺增加和叶片氮浓度降低显著相关的木质部汁液离子成分。干旱植株黎明前叶片脱落酸含量在7天DAWI时增加100 - 200 ng g(-1)干重，此时气孔导度降低，而午间叶片水势尚未出现任何显著下降。根据观察到的顺序，提出了一系列信号事件，最终通过干旱条件下氮供应减少和植物生长调节剂的相互作用导致气孔关闭和叶片表面积减小。
