盐分不均匀分布对紫花苜蓿生长和离子特征的影响 孙娟娟 于林清 赵金梅 刘洪林 张英俊 中国农业科学院草原研究所 中国农业大学动物科学技术学院草业科学系 摘 要： 【目的】土壤盐分浓度在空间上呈不均匀分布, 研究不均匀盐胁迫对紫花苜蓿生长、水分吸收、光合作用以及根叶部位 K+和 Na+的影响, 探讨紫花苜蓿适应根部不均匀盐胁迫的生理机制, 为紫花苜蓿耐盐品种培育及改良盐碱地紫花苜蓿种植技术提供理论依据方法】通过水培法, 将紫花苜蓿幼苗的根均匀分成两部分置于分根装置中, 给予两侧根部相同或不同浓度的 NaCl 处理, 设置对照 (0/0) 、低盐胁迫根部分别为 0 mmol·L-1NaCl (0/400) 和 100 mmol·L-1NaCl (100/300) 的不均匀盐胁迫处理和均匀的 200 mmol·L-1NaCl 胁迫处理 (200/200) , 处理 7 d 后取样分析结果】不均匀盐胁迫与均匀盐胁迫均抑制了紫花苜蓿生长, 导致水分吸收减少、叶片 Na+浓度增加和叶片 K+浓度减少然而, 0/400 处理紫花苜蓿地上部分鲜重、水分吸收分别比 200/200 处理提高了 24.3%和 44.2%, 其叶片 Na+浓度比 200/200 处理降低了 53.6%、叶片 K+浓度与 200/200 处理无显著差异。
0/400 处理 0 侧根部水分吸收比对照提高12.3%、Na +浓度是对照的 10.5 倍、K +浓度与对照无显著差异100/300 处理紫花苜蓿地上部分鲜重、整株水分吸收、叶片 K+浓度均与 200/200 处理无显著差异100/300 处理叶片 Na+浓度比 200/200 处理提高了 31.0%100/300 处理 100侧根部水分吸收比对照降低了 33.9%、Na +浓度是对照的 39.5 倍、K +浓度比对照降低了 31.3%0/400、100/300 与 200/200 的蒸腾速率、气孔导度和胞间二氧化碳浓度无显著差异且均显著低于对照, 而 0/400 的净光合速率与 200/200 无显著差异, 均显著高于对照, 100/300 的净光合速率与对照无显著差异结论】紫花苜蓿根部平均盐分浓度为 200 mmol·L-1NaCl 时, 一侧根部 NaCl 浓度等于或高于其半致死浓度, 另一侧根部 NaCl 浓度为 0 mmol·L-1时, 不均匀盐胁迫缓解了根部高浓度盐胁迫对紫花苜蓿生长的抑制, 当低盐胁迫根部 NaCl 浓度为 100 mmol·L-1时, 不均匀盐胁迫不能够缓解根部高浓度盐胁迫对紫花苜蓿生长的抑制。
关键词： 紫花苜蓿; 异质性盐胁迫; 水分吸收; Na+调控; 光合参数; 作者简介：孙娟娟;E-mail:sunjuanjuan@作者简介：张英俊;Tel:010-62733380;E-mail:zhangyj@收稿日期：2017-03-21基金：国家牧草产业技术体系 (CRAS-35) Effects of Heterogeneous Root Zone Salinity on Plant Growth and Ion Characteristic in AlfalfaSUN JuanJuan YU LinQing ZHAO JinMei LIU HongLin ZHANG YingJun Institute of Grassland Research, Chinese Academy of Agricultural Sciences; Department of Grassland Science, College of Animal Science and Technology, China Agricultural University; Abstract： 【Objective】Soil salinity is spatially heterogeneous. The effects of heterogeneous salinity on the growth, water uptake, photosynthetic parameter, K+ and Na+ concentration in leaf and root of alfalfa plants were determined to improve understanding of non-uniform salt stress tolerance mechanisms of alfalfa, so as to provide theoretical evidence for breeding the new alfalfa varieties tolerant to salt, and to improve alfalfa plant in salinity areas. 【Method】Plant growth, water uptake, tissue ionic concentrations were studied in alfalfa plants grown hydroponically for 7 days using a split-root system, with uniform 0 and 200 mmol·L-1 NaCl or heterogeneous 0/400 and 100/300 mmol·L-1 NaCl. 【Result】Neither uniform salinity or heterogeneous salinity inhibited alfalfa growth, decreased water uptake, increased leaf Na+ concentration and decreased leaf K+ concentration. Compared with uniform 200 mmol·L-1 NaCl, 0/400 treatment significantly increased the alfalfa shoot fresh weight and whole plant water uptake. Shoot fresh weight and whole plant water uptake under 0/400 treatment were 24.3% and 44.2%, respectively, higher than 200/200 treatment. The leaf Na+ concentration in 0/400 treatment was 53.6% lower than in 200/200 treatment, and the leaf K+ concentration was similar with 200/200 treatment. But water uptake in non-salinity root was 12.3% higher and Na+ concentration in non-salinity root of 0/400 treatment was 10.5-fold higher than control, whereas K+ concentration in non-salinity root of 0/400 treatment was similar with control. There were no significantly differences of shoot fresh, water uptake and leaf K+ concentration between 100/300 and 200/200 treatment, but leaf Na+ concentration in 100/300 treatment were 31.0% higher than in 200/200 treatment. Water uptake were 33.9% lower, K+ concentration was 31.3% lower, and Na+ concentration were 39.5-fold in low-salinity root of 100/300 treatment, compared with control. Transpiration rate, stomatal conductance and intercellular CO2 concentration of 0/400, 100/300 and 200/200 treatment were similar with each other and significantly lower than control, however, net photosynthetic of 0/400 and 200/200 were significantly higher than control, and net photosynthetic of 100/300 were similar with control.【Conclusion】When root average salinity was 200 mmol·L-1 NaCl, the NaCl concentration of high salinity root were equal or greater than half lethal concentration, heterogeneous salinity can improve alfalfa plant growth when low salinity root under 0 mmol·L-1 NaCl, but heterogeneous salinity can not improve alfalfa plant growth when low salinity root under 100 mmol·L-1 NaCl.Keyword： alfalfa; heterogeneous salinity; water uptake; Na+ regulation; photosynthetic parameter; Received： 2017-03-210 引言【研究意义】紫花苜蓿 (Medicago sativa L.) 是世界广泛栽培的多年生饲草作物之一, 由于其适应性广、产草量高, 且富含蛋白质、维生素和矿物质等营养物质, 被誉为“牧草之王”。
中国苜蓿种植面积约为 3.77×10hm, 居各类人工草地之首[1]紫花苜蓿生长及种植的多数地区都受到土壤盐渍化的影响[2]2015 年, 甘肃、内蒙古、新疆、宁夏、黑龙江、河北等 6 省的优质苜蓿种植面积占全国的 89.8%, 此六省的盐渍土面积约占全国盐渍土面积的 65.7%[3]自然界中土壤盐分在时空分布上呈不均匀状态存在[4], 并且植物根区土壤盐分也呈不均匀分布[5-8]地下水位的波动[9]、土层深度、水平距离的不同、季节变化[10]、灌溉、降雨[11]以及植物本身对 Na 的过滤[12]均会导致土壤盐分的不均匀分布例如, 在苜蓿田, 从地表到 1.2 m 的土层深度, 土壤电导率值变化范围为 1.1 到 11.7 d·S·m-1[13];在盐碱滩垂直方向 1 m 的范围内, 土壤电导率变化范围为 70—214 d·S·m-1[14];在旱地灌木地水平方向 10 m 的范围内, 土壤电导率变化范围为 6—130 d·S·m-1[15]研究表明, 植物能够在盐土中维持生长, 土壤盐分的不均匀分布起着极为重要的作用, 当植物生长在均匀的高浓度盐土中时将面临死亡[16-17]。