盐地碱蓬二型性种子的萌发和休眠及生态适应特性

Ecological Adaptation in Dormancy and Germination of Dimorphic Seeds of Suaeda salsa

二型性种子可能增强植物(尤其是盐生植物)应对难于预测环境变化的能力。该研究以运城盐湖盐地碱蓬(Suaeda salsa)二型性种子(黑色和棕色)为材料,采用室内观察和萌发方法对两种种子的形态、休眠和萌发特性进行比较,以揭示盐生植物二型性种子对盐渍化环境的适应对策。结果表明:(1)黑色种子体积小,种皮角质有光泽,而棕色种子体积大,种皮膜质无光泽。(2)新成熟的棕色种子在实验温度范围内萌发率均超过90%,而黑色种子仅在15/25℃下萌发最高(但低于85%),并且棕色种子萌发速度较黑色更快。(3)低盐(<0.39mol/L)条件下,光照或黑暗对棕色种子萌发没有显著影响;高盐(>0.39mol/L)条件下,棕色种子在黑暗中的萌发显著高于光照环境,而黑色种子在光照条件下的萌发率显著高于黑暗;所有温度和光照处理中,2种种子均随盐分浓度的升高而下降,但棕色种子在盐分浓度为0.78mol/L时萌发率仍能够达到30%以上,而黑色种子在盐分浓度大于0.59mol/L时几乎不萌发。(4)棕色种子为非休眠种子,而黑色种子具有非深度生理休眠特性;划破种皮、干储、低温层积和GA3处理均能够提高黑色种子的萌发率。研究发现,盐地碱蓬通过二型性种子休眠和萌发行为上的差异,采用"两头下注"对策提高其对盐渍化异质生境的适应性。

Dimorphic seeds may help plants to cope with unpredictable environmental changes,especially for halophytes.Mature seeds（black and brown）of Suaeda salsainhabiting in the Yuncheng Salt Lake were used to reveal adaptive strategies of the halophyte with dimorphic seeds in saline habitat by combining laboratory observation and germination experiments.The morphology,dormancy and germination characteristics of dimorphic seeds were compared.The results showed that：（1）black seeds were small and had keratose and glossy testa,while brown seeds were larger and had membranous and lusterless testa.（2）Germination of freshly matured brown seeds was more than 90%across the experimental temperature ranges,while germination of black seeds was only the highest at 15/25℃（less than 85%）,and brown seeds had higher germination rate than black seeds.（3）Alternating of light and darkness or full darkness had no significant effect on germination of brown seeds under low salt conditions（〈0.39mol/L）.However,ger-mination of black seeds under light was significantly higher than that under darkness（P〈0.05）.Responses of dimorphic seeds to saline stress were different,germination of brown seeds was more than 30%in0.78mol/L NaCl solution,while black seeds did not germinate beyond 0.59mol/L.（4）Brown seeds were non-dormant,but black seeds had non-deep physiological dormancy.Seed coat scarification,dry storage,cold stratification and GA3 significantly promoted germination of black seeds.Our study revealed that S.salsaadopts＂bet-hedging＂strategy（differences in dormancy and germination behavior of dimorphic seeds）to increase the adaptability to the heterogeneous habitat.