模拟干旱胁迫下六个种源梓树种子萌发特性及地理变异研究

Effect of simulated drought stress on seed germination andgeographical variation of six provenances of Catalpa ovata

该研究采用聚乙二醇(PEG-6000)模拟干旱胁迫,测定了发芽率、发芽势和胚根长度等指标,运用相关性分析、聚类分析和隶属函数法综合评价梓树六个种源种子萌发期的抗旱性大小,初步筛选出抗旱性较强的种源。结果表明:随着溶液水势的降低,六个种源种子的发芽率、发芽势、相对发芽率、发芽指数、活力指数表现为持续下降趋势;除河南洛阳种源的胚根、胚轴长度以及甘肃正宁种源的胚根长度外,其余种源胚根、胚轴长度均表现为逐渐下降趋势;溶液水势为-1.0 MPa时,河南洛阳种源失活,其余种源各指标趋于一致。将各种源种子发芽特性与原产地地理环境因子进行相关分析表明,种子活力指数与经度、纬度呈显著正相关(0.903和0.871),经度、纬度较大的种源活力更强、抗旱性更佳;年均气温越高,种子发芽率和活力均降低;年降雨量与种子的发芽率和活力指数呈中偏弱的负相关,但与胚根和胚轴的生长呈中等正相关;温度和降雨量对梓树种子的抗旱性有一定影响,主要体现在年均温和年降雨量越低,种子的发芽率也越低;初步发现处于干旱和寒冷等相对恶劣环境下的梓树种源表现为以提高种子发芽率和降低种子胚生长活性的调节机制来适应不良环境。运用聚类分析及隶属函数法对六个种源梓树种子萌发期进行抗旱性综合评价,辽宁恒仁种源种子抗旱性最强,河南洛阳种源种子抗旱性最弱。综上结果认为,梓树六个种源抗旱性差异明显,温度和降雨量在一定程度上影响了种子萌发的抗旱性。

In this study,polyethylene glycol(PEG-6000)was used to simulate drought stress,the germination percentage,germination potential and radicle length were measured.Correlation analysis,cluster analysis and membership function method were used to comprehensively evaluate six provenances of Catalpa ovata.The most resistant sources of drought resistance were screened good rootstocks out for the grafting of Chinese C.bungei,to promote the breeding,and to lay a material foundation for its large-scale application.The results were as follows:The germination rate,germination potential,relative germination rate,germination index and vigor index of six provenances of C.ovata seeds decreased with a trend continuous decline.Except for the radical length,hypocotyl length of the Luoyang in Henan provenance,and the radical length of the Zhengning in Gansu provenance.The length of radicle and hypocotyl of other provenances showed a trend of gradual decrease.When the osmotic stress was-1.0 MPa,the Luoyang in Henan provenance was deactivated,and the indexes of another provenances’tendency to be consistent.The correlation between the germination characteristics of each group and the geographical environment factors of origin indicated that there was a significant positive correlation between vigor index,longitude and latitude(0.903 and 0.871).The higher average annual temperature,the lower seed germination rate and vigor.Annual precipitation was negatively correlated with seed germination rate and vigor index,but moderately positive correlated with the growth of radicle and hypocotyl.Temperature and precipitation affected the drought resistance of seeds of C.ovata to some extent,mainly reflected in the lower annual temperature and annual precipitation,the lower germination rate of seeds.It was preliminarily found that provenances of C.ovata in the relatively harsh environment of drought and cold showed the regulation mechanism to improve seed germination rate and reduce the growth activity of seed embryo to adapt to the unfavorable environment.The results of cluster analysis and membership function method were used to comprehensively evaluate the drought resistance of C.ovata seeds in six groups.The seeds of Liaoning in Hengren provenance had the strongest drought resistance,while the Luoyang in Henan provenance had the weakest drought resistance.In summary,the drought resistance of six provenances of C.ovata is obvious,temperature and rainfall affect the drought resistance of seed germination to some extent.The provenance with strong drought resistance are selected to be the rootstocks of C.bungei breeding and lays a material foundation for the large-scale application of C.bungei.