Hydraulic conductivity of rice roots
Hydraulic conductivity of rice roots
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DOI：
10.1093/jexbot/52.362.1835
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发表时间：
2001-09-01
影响因子：
6.9
通讯作者：
Lafitte, R
中科院分区：
文献类型：
--
作者：
Miyamoto, N;Steudle, E;Lafitte, R
采用压力室和根压探针技术测定了水稻根系的导水率（每平方米根表面积的根导水率）。两种水稻（Oryza sativa L.）品种（一个高地品种，cv. Azucena和一个低地品种，变异。IR 64）在500 μ mol m（-2）s（-1）PAR和27 ℃和22 ℃的昼夜温度下生长31-40 d。在稳态和瞬态水流条件下测定了根系LPr。不同的生长条件（水培和气培培养）没有造成明显的差异，在任何品种的根解剖。从水力（静水）和渗透水流中获得的根LPr值为10（-8）m s（-1）MPa-1的数量级，并且在使用不同技术时相似。与其他草本植物相比，水稻根系单位根表面积的水力阻力更大。这些数据表明，水稻根的整体导水率低是由于存在质外体障碍的外部根部分（外皮层和厚壁组织（纤维）组织）和一个强烈发达的内皮层，而不是通气组织的存在。根据复合运输模型的根，适应更高的蒸腾需求的能力，从地上部应是有限的，因为有最小的变化，根LPr取决于是否静水压力或渗透力的作用。这可能是水稻即使在淹水条件下，地上部也缺水的原因之一。
A pressure chamber and a root pressure probe technique have been used to measure hydraulic conductivities of rice roots (root LPr per m(2) of root surface area). Young plants of two rice (Oryza sativa L.) varieties (an upland variety, cv. Azucena and a lowland variety, cv. IR64) were grown for 31-40 d in 12 h days with 500 mu mol m(-2) s(-1) PAR and day/night temperatures of 27 degreesC and 22 degreesC. Root LPr was measured under conditions of steady-state and transient water flow. Different growth conditions (hydroponic and aeroponic culture) did not cause visible differences in root anatomy in either variety. Values of root LPr obtained from hydraulic (hydrostatic) and osmotic water flow were of the order of 10(-8) m s(-1) MPa-1 and were similar when using the different techniques. In comparison with other herbaceous species, rice roots tended to have a higher hydraulic resistance of the roots per unit root surface area. The data suggest that the low overall hydraulic conductivity of rice roots is caused by the existence of apoplastic barriers in the outer root parts (exodermis and sclerenchymatous (fibre) tissue) and by a strongly developed endodermis rather than by the existence of aerenchyma. According to the composite transport model of the root, the ability to adapt to higher transpirational demands from the shoot should be limited for rice because there were minimal changes in root LPr depending on whether hydrostatic or osmotic forces were acting. It is concluded that this may be one of the reasons why rice suffers from water shortage in the shoot even in flooded fields.