Abstract:

Drought stress were simulated using different osmotic stresses (0, -0.2, -0.4, -0.6, -0.8 and -1.2 Mpa) of PEG-6000, and a gradient of exogenous Ca²⁺ (0, 5, 15, 30 and 50 mmol·L^-1) was installed to simulate the high calcium environments. The effects of different PEG-6000 and CaCl₂ concentrations on the seed germination characteristics of Lespedeza bicolor and their interactions were studied here. The results showed that the seed germination rate, germination potential, germination index, and vigor index of Lespedeza bicolor significantly decreased with the increase of osmotic stress. The medium or low concentrations of exogenous Ca²⁺ (< 30 mmol·L^-1) had lesser effects on the seed germination parameters of Lespedeza bicolor, whereas the higher concentrations of exogenous Ca²⁺ (50 mmol·L^-1) had inhibition effect on the seed germination. The four germination indexes of Lespedeza bicolor under drought stress increased at first and then decreased with the increase of exogenous Ca²⁺. The four germination indexes of Lespedeza bicolor were the highest when the concentration of exogenous Ca²⁺ was 15 mmol·L^-1; The four germination indexes of Lespedeza bicolor decreased when the concentration of exogenous Ca²⁺ was from 30 to 50 mmol·L^-1, and the trend of the decrease was obvious with the increase of drought stress. Therefore, the exogenous Ca²⁺ (15 mmol·L^-1 ) can be used to soak Lespedeza bicolor seeds before sowing in moderate drought area to improve the emergence rate of Lespedeza bicolor.

Key words: Lespedeza bicolor, Drought stress, Exogenous calcium, Seed germination

摘要：

采用聚乙二醇(PEG-6000)0, -0.2, -0.4, -0.6, -0.8和-1.2 Mpa模拟干旱胁迫,以CaCl₂浓度0, 5, 15, 30和50 mmol·L^-1为外源钙离子梯度,研究干旱、外源钙及二者交互作用对二色胡枝子(Lespedeza bicolor)种子萌发的影响,以探寻减缓干旱胁迫抑制二色胡枝子种子萌发的最佳外源钙施入量.结果表明:随着干旱胁迫强度增加,二色胡枝子种子发芽率、发芽势、发芽指数及活力指数均显著低于对照.正常水分条件下,中低浓度外源钙(< 30 mmol·L^-1)对二色胡枝子种子萌发无显著影响,而高浓度外源钙(50 mmol·L^-1)对种子萌发具有抑制作用.干旱胁迫下,随外源钙浓度增加,二色胡枝子种子4个萌发指标呈先升高后降低的趋势,在外源钙浓度为15 mmol·L^-1时,种子发芽的各项指标均达到最大值,而当外源钙浓度在30~50 mmol·L^-1时,二色胡枝子种子4个萌发指标均呈下降趋势,并且随着干旱胁迫加剧,下降趋势更明显.因此,在二色胡枝子生产利用中,对于中等干旱条件的地区,可以在播种前利用15 mmol·L^-1的外源钙浸种,以提高出苗率.

关键词: 二色胡枝子, 干旱胁迫, 外源钙, 种子萌发