极度濒危植物狭叶坡垒种子脱水敏感性研究

Study on Desiccation Sensitivity of Seeds of Extremely Endangered Plant Hopea chinensis

狭叶坡垒(Hopea chinensis)种子为典型的顽拗性种子。为了解其脱水敏感性及生理特性,测定自然脱水条件下狭叶坡垒种子含水率、萌发参数及生理指标变化情况。结果表明,狭叶坡垒种子初始含水率为42.57%,初始萌发率为90.00%;脱水4天时,种子含水率为34.67%,萌发率为83.33%;脱水8天时,种子含水率为31.21%,萌发率为51.67%;脱水16天时,种子完全失去活力。随种子含水率降低,种子萌发率、萌发指数和活力指数等逐渐减小,相对电导率和丙二醛(MDA)含量逐渐上升,超氧化物歧化酶(SOD)活性呈波动性升降,过氧化氢酶(CAT)活性呈先升后降的趋势。脱水前期,CAT是狭叶坡垒种子的敏感性保护酶;脱水中期,主要通过提高SOD活性抵御损伤;脱水后期,损伤超出种子耐受范围,种子逐渐失活。狭叶坡垒种子对脱水高度敏感,严重脱水(脱水10天后)会加剧细胞膜损伤,降低抗氧化酶活性,种子失去活力。

Hopea chinensis seeds are typical recalcitrant seeds.In order to understand desiccation sensitivity and physiological characteristics of H.chinensis seeds,changes of moisture content,germination parameters and physiological indexes of H.chinensis seeds under natural desiccation condition were measured.Results showed that initial moisture content of H.chinensis seeds was 42.57%,and initial germination rate was 90.00%.When 4 days of desiccation,moisture content of seeds was 34.67%,and germination rate was 83.33%.When 8 days of desiccation,moisture content of seeds was 31.21%,and germination rate was 51.67%.When 16 days of desiccation,seeds completely lost vigor.With decrease of moisture content of seeds,seed germination rate,germination index and vigor index gradually decreased,relative electrical conductivity and MDA content gradually increased,SOD activity fluctuated,and CAT activity increased firstly and then decreased.In early stage of desiccation,CAT was sensitive protective enzyme of H.chinensis seeds,while in middle stage of desiccation,damage was resisted by increasing SOD activity.In later stage of desiccation,damage was beyond tolerance range of seeds,and seeds were gradually inactivated.H.chinensis seeds were highly sensitive to desiccation,and severe desiccation(after 10 days of desiccation)would aggravate cell membrane damage and reduce activities of antioxidant enzymes,resulting loss of seed vigor.