Zhang Suiqi, Shan Lun
Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Northwest Sci-Tech University of Agriculture and Forestry, Yangling 712100, China.
Ying Yong Sheng Tai Xue Bao. 2003 Sep;14(9):1503-6.
It is realized in recent years that roots play an important role in the control of shoot growth and development, not only because they can continuously provide the shoot with water and nutrients, but also because some chemical messengers are produced in roots to response soil drought stress and transported through transpiration stream to shoot where physiological processes are regulated. Extensive studies showed that the decrease of leaf conductance was closely related to the increase of xylem ABA concentration, suggesting that ABA can act as a water stress signal to regulate the physiological response of shoot. Fertilizer plays an important role in increasing crop yield and water use efficiency (WUE) on dry-land farming. It is not clear, however, whether the application of N fertilizer can affect the root's signal intensity in drought stress and thus regulate its stomatal responses. Experiment with 3 water levels (35%, 55% [symbol: see text] 75% +/- 5% of field capacity) and 2 N fertilizer levels (high N and low N) was designed to investigate the effect of soil drought and N nutrition on endogenous hormone concentration (ABA and ZRs) and stomatal conductivity of maize under potted conditions. The results showed that the application of N significantly increased the stomatal conductivity of maize leaf under both drought and watered conditions. Meanwhile, it markedly decreased the ABA concentration in root xylem sap, but increased ABA concentration in leaf of maize under soil drought conditions. The application of N decreased ZRs concentration in root xylem sap as well, which means that ZRs did not play a role in counteractive to ABA under soil drought conditions. The lower ABA concentration in root xylem sap of high N maize rather than the higher ABA concentration in maize leaf accounted for the higher stomatal conductivity of high N maize leaf under soil drought conditions.
近年来人们认识到，根系在地上部生长发育的调控中发挥着重要作用，这不仅是因为它们能持续为地上部提供水分和养分，还因为根系会产生一些化学信使来响应土壤干旱胁迫，并通过蒸腾流运输到地上部，在那里调节生理过程。大量研究表明，叶片导度的降低与木质部脱落酸（ABA）浓度的增加密切相关，这表明ABA可作为水分胁迫信号来调节地上部的生理响应。肥料在提高旱地作物产量和水分利用效率（WUE）方面起着重要作用。然而，氮肥的施用是否会影响干旱胁迫下根系的信号强度，进而调节其气孔响应尚不清楚。本试验设置了3个水分水平（田间持水量的35%、55% [符号：见原文] 75%±5%）和2个氮肥水平（高氮和低氮），旨在研究盆栽条件下土壤干旱和氮素营养对玉米内源激素浓度（ABA和玉米素核苷，ZRs）及气孔导度的影响。结果表明，无论在干旱还是浇水条件下，施用氮肥均显著提高了玉米叶片的气孔导度。同时，氮肥显著降低了根木质部汁液中的ABA浓度，但在土壤干旱条件下却增加了玉米叶片中的ABA浓度。氮肥的施用也降低了根木质部汁液中的ZRs浓度，这意味着在土壤干旱条件下ZRs在对抗ABA方面未发挥作用。在土壤干旱条件下，高氮玉米根木质部汁液中较低的ABA浓度而非叶片中较高的ABA浓度，导致了高氮玉米叶片较高的气孔导度。
