Calvo-Polanco Monica, Sánchez-Romera Beatriz, Aroca Ricardo
Estación Experimental del Zaidín (CSIC), Department of Soil Microbiology and Symbiotic Systems, Granada, Spain.
PLoS One. 2014 Mar 4;9(3):e90631. doi: 10.1371/journal.pone.0090631. eCollection 2014.
Plants respond to salinity by altering their physiological parameters in order to maintain their water balance. The reduction in root hydraulic conductivity is one of the first responses of plants to the presence of salt in order to minimize water stress. Although its regulation has been commonly attributed to aquaporins activity, osmotic adjustment and the toxic effect of Na+ and Cl- have also a main role in the whole process. We studied the effects of 30 mM NaCl on Phaseolus vulgaris plants after 9 days and found different responses in root hydraulic conductivity over-time. An initial and final reduction of root hydraulic conductivity, stomatal conductance, and leaf water potential in response to NaCl was attributed to an initial osmotic shock after 1 day of treatment, and to the initial symptoms of salt accumulation within the plant tissues after 9 days of treatment. After 6 days of NaCl treatment, the increase in root hydraulic conductivity to the levels of control plants was accompanied by an increase in root fructose content, and with the intracellular localization of root plasma membrane aquaporins (PIP) to cortex cells close to the epidermis and to cells surrounding xylem vessels. Thus, the different responses of bean plants to mild salt stress over time may be connected with root fructose accumulation, and intracellular localization of PIP aquaporins.
植物通过改变其生理参数来应对盐胁迫，以维持水分平衡。根系水力传导率的降低是植物对盐分存在的早期反应之一，目的是尽量减少水分胁迫。虽然其调节通常归因于水通道蛋白的活性，但渗透调节以及Na+和Cl-的毒性作用在整个过程中也起着主要作用。我们研究了30 mM NaCl处理9天后对菜豆植株的影响，发现根系水力传导率随时间有不同的反应。NaCl处理后，根系水力传导率、气孔导度和叶片水势最初和最终的降低，分别归因于处理1天后的初始渗透冲击，以及处理9天后植物组织内盐分积累的初始症状。NaCl处理6天后，根系水力传导率增加到对照植株的水平，同时根系果糖含量增加，且根细胞质膜水通道蛋白（PIP）在靠近表皮的皮层细胞和木质部导管周围细胞内定位。因此，菜豆植株对轻度盐胁迫随时间的不同反应可能与根系果糖积累和PIP水通道蛋白的细胞内定位有关。
