高低纬度种源互花米草种子萌发特性及其对温度的响应

Seed germination characteristics of Spartina alterniflora from high and low latitude populations in relation to temperature

经过40多年的扩散,互花米草(Spartina alterniflora)已广泛分布到中国海岸潮间带滩涂,纵跨20个纬度,其入侵已对我国滨海湿地生态系统造成严重威胁。种子萌发是影响互花米草成功入侵不同纬度地理区域的关键阶段,而温度是影响种子萌发的主要因素之一,并可能使得位于分布区域内的高纬度和低纬度互花米草种子萌发特性产生差异。为了探究高低纬度的互花米草种子萌发特性对温度的响应,本研究以位于东营(38.0°N)和雷州(20.9°N)两地的互花米草为对象,采用纸上发芽法,测定了不同温度(5、15、25℃)处理下高低纬度种源互花米草种子的萌发率、萌发指数和平均萌发时间。结果表明:(1)种源对萌发率和萌发时间有显著影响(P<0.0001),高纬度种源种子萌发率高于低纬度种源种子,但比低纬度种源的种子需要更长的萌发时间。(2)在5~25℃内,温度升高显著促进了高低纬度种源种子的萌发率和萌发指数(P<0.0001),并缩短了萌发时间,提早了萌发高峰期。(3)温度和种源的交互作用对萌发率有显著影响(P<0.001),随着温度的升高,种源之间的萌发特性差异增大。温度对萌发特性的作用可能是因为升高温度提高了酶的活性,从而加快了萌发进程,并以萌发特性改变的形式表现出来。高低纬度种源种子萌发特性的差异表明,高低纬度的互花米草种群可能已对入侵地不同地理区域的气候产生局域适应。推测高纬度地区互花米草入侵扩散的风险高于低纬度地区。

Spartina alterniflora is distributed over 20 degrees( 20°N to 39°N) of latitude after 40 years of deliberate planting and natural dispersal,which poses a serious threat to coastal and wetland ecosystems in China. Seed germination,a critical stage determining the invasion of S. alterniflora into different latitudes,is affected by temperature. Seed germination characteristics of S.alterniflora would be different at the high latitude and low latitude regions. We explored the response of seed germination of S. alterniflora populations from high and low latitude to temperature,with seeds from high-latitude provenance at Dongying( 38. 0° N) and low-latitude provenance at Leizhou( 20.9°N). We measured the germination percentage,germination index,and mean germination time of S. alterniflora seeds under different temperatures( 5,15,25 ℃) . The results showed that:( 1) Provenances significantly affected germination percentage and germination time( P<0.0001). Seeds from high-latitudinal provenance had higher germination percentage and longer mean germination time than of those from low-latitudinal provenance.( 2) Within 5-25 ℃,rising temperature significantly promoted germination percentage and germination index( P<0.0001),shortened the mean germination time,and advanced the germination peak.( 3)Temperature and provenance significantly interacted to affect germination percentage( P<0.001).The effect of temperature on germination characteristics might be due to the enhanced enzyme activity at higher temperature,which accelerated the germination process and altered germination characteristics. The difference of seed germination characteristics between high-and low-latitudinal provenances indicated that S. alterniflora adapted to local climate of different geographical areas. Our results suggest that the risk of invasion and diffusion of S. alterniflora at high latitude is higher than that at low latitude.