西藏3种野生牧草苗期对干旱胁迫的响应

通过气候培养箱盆栽试验,探究了干旱胁迫对西藏3种野生牧草(赖草(Leymus secalinus)、垂穗披碱草(Elymus nutans)和老芒麦(Elymus sibircus))苗期生长特性和生理指标的影响,并对其抗旱能力进行综合评价,旨在为选育抗旱性强的优良牧草种质资源和人工草地建植提供科学理论依据。研究发现,随着干旱胁迫时间的增加,土壤相对含水量呈现先快速下降后缓慢下降的变化趋势,种植不同牧草的土壤含水量变化值也不相同。3种野生牧草幼苗的株高变化量、植株含水量和叶绿素(Chl)含量均随干旱胁迫时间的增加而呈现下降趋势;植物体内游离脯氨酸(Pro)含量、丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性均表现为随着干旱胁迫时间增加而增大;可溶性糖含量均表现为随干旱胁迫时间的增加呈现先减小后增大的变化趋势:干旱胁迫第5天的可溶性糖含量最低,但老芒麦干旱胁迫第20天时的可溶性糖含量仍低于对照;垂穗披碱草可溶性蛋白含量随着干旱胁迫时间的延长而增加,老芒麦和赖草体内可溶性蛋白含量呈现先减小后增大的变化趋势,老芒麦在干旱胁迫第10天时可溶性蛋白含量最低,而干旱胁迫第5天时赖草体内可溶性蛋白含量最低。用隶属函数法对干旱胁迫下3种野生牧草苗期8个指标进行综合评价,其抗旱性强弱顺序依次为:赖草垂穗披碱草老芒麦。结果表明3种牧草中赖草的抗旱能力最强,适合在西藏干旱地区种植;但由于赖草有性繁殖能力较低,而垂穗披碱草有性繁殖能力较强,可以作为西藏干旱、半干旱地区生态恢复的首选草种。

Drought stress responses of the seedlings of three wild forages in Tibet

In the present study, the effects of drought stress on seedling growth and physiology of three wild forages (Leymus secalinus, Elymus nutans, and E. sibiricus) in Tibet were investigated using pot experiments in a climate incubator. The drought resistance of the three forages was evaluated. One of the objectives of this study was to contribute to the breeding of drought-tolerant forage germplasm. The results showed that with increased drought stress, the relative water content of the soil decreased rapidly initially, and then slowly, and varied among different species. The average growth rate, plant water content, and leaf chlorophyll content decreased, but the proline content, MDA content, and SOD activity of the plants increased, as drought stress was prolonged. Moreover, the soluble sugar content of the plants decreased initially, and then increased as drought stress was prolonged. Briefly, the soluble sugar minimum values of all the plants occurred at day 5 after drought stress treatment, but soluble sugar content of E. sibiricus was still lower than that of the control after 20 days of drought stress treatment. The soluble protein content of E. nutans increased as drought stress was prolonged, but the soluble protein content of L. secalinus and E. sibiricus decreased initially and then increased with the duration of drought stress. The soluble protein contents of E. sibiricus were the lowest during the first 10 days of drought stress, whereas the soluble protein contents of L. secalinus were at the minimum level during the first 5 days of drought stress. By using the eight indicators for the three wild forage seedlings under drought stress, we performed a comprehensive evaluation of drought tolerance of the three wild forage seedlings with subordinate function and indicated the order of drought tolerance as L. secalinus > E. nutans > E. sibiricus. Therefore, the drought resistance of L. secalinus was the strongest, and it was suitable for planting in the arid regions of Tibet, but L. secalinus and E. nutans with lower sexual reproduction rates were suitable grass species for ecological restoration in arid and semi-arid areas in Tibet.