不同光照处理下青藏高原克隆植物黄帚橐吾(Ligularia virgaurea)种子大小对其幼苗生长的影响

Seed size effect on seedling growth under different light conditions in the clonal herb Ligularia virgaurea in Qinghai Tibet Plateau

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明:(1)在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。(2)黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量(TB)大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比(R/S)大于小种子幼苗。(3)黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率(RGR)较大于大种子幼苗,但叶面积比率(LAR)、叶面积干质量比(SLA)、叶干质量(LWR)差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。

We studied the influence of seed size on germination, seedling growth, and seedling responses to light in Ligularia virgaurea, a clonal herb native to the Qinghai Tibet Plateau. （ 1 ） Under unshaded conditions, large seeds had significantly （p 〈0.01 ） higher rates of germination than did small seeds. Both large and small seeds showed significantly reduced levels of germination under shaded （ by shadecloth） conditions. The magnitude of this effect was greater for small seeds than for large seeds. Germination of small seeds （ 1.75 mg） was reduced by one eighth, while germination of large （2.80mg） seeds was only reduced by one eleventh. （2） Seedlings from large seeds had significantly higher rates of biomass accumulation （g·d^-1） than did seedlings from small seeds. This, combined with larger initial masses gave seedlings from large seeds significantly greater total biomass after 60 days of growth. Seedlings from large and small seeds also differed in biomass allocation. After 60 days of growth （ under both shaded and unshaded conditions）, seedlings from larger seeds had proportionally larger root mass and proportionally smaller leaf mass than did seedlings from small seeds. （ 3 ） Seedlings from small seeds have higher relative growth rates （ RGR; g·d^-1 ·d^-1 ） than do seedlings from large seeds, under both shaded and unshaded conditions. By contrast, there was no significant difference between leaf area ratio （LAR） ; specific leaf area （SLA） or leaf weight ratio （LWR） between seedlings from small vs large seeds. RGR, LAR, SLA and LWR were all significantly higher in seedlings grown under shaded conditions than in seedlings grown in full light.