Effects of seed weight on seedling growth under different nutrient conditions in twenty-four species of Compositae in an Alpine Meadow

ZHANG ShiTing1, DU GuoZhen1*, CHEN JiaKuan2, XIONG ZhiYuan1anzhou730000, China; 2. Fudan University Biodiversity Science Institute, Shanghai20043, China).  

Effects of seed weight on seedling growth were investigated in 24 common species of Compsoitae in an alpine meadow on the Tibet plateau. Seedlings were cultured in deionized water, washed sand with added distilled water, washed sand with added halfstrength Hoagland solution and washed sand with added standard Hoagland solution. Seedling growth was observed after 10 days, 20 days and 30 days. The results were as follows:(1) There was a highly significant positive correlation between log seed weight and log seedling weight with a geometrical mean regression after all three different observation periods (p0001), regardless of culture media, that is, heavierseeded species had larger seedlings than lighterseeded species. The relation between seed weight and seedling weight remained relatively constant in deionized water and decreased continuously in the other three culture media after 10d, 20d and 30d. This is probably because the seedlings in deionized water completely depend on the seed reserve, while seedlings in other three culture media can absorb external nutrients when the seed reserve is used up.(2) There were significant negative correlations between log seed weight and log relative growth rate in all the culture media after 10d, 20d and 30d, but these correlations were only weak after 10d and 20d in deionized water. It seems that relative growth rate of any species was relatively constant, despite variations in nutrient supply, suggesting that relative growth rate may be a conservative character of a species. However, we could account neither for the weakness of the correlation between seed size and relative growth rate in deionized water after 10d and 20d, compared to 30d, nor why this was not apparent in the other three culture media.(3) There were no significant correlations between log seed weight and log root shoot ratio, except for a significant positive correlation after 10d in deionized water. So the advantage of large seeds in alpine meadows does not lie in higher root allocation in early seedling growth, as found in arid zones in other studies.

【Fund】： 国家自然科学重大研究计划资助项目(90202009);; 甘肃省"九五"重点攻关资助项目(GK-971-2-35A)~~
【CateGory Index】： Q945

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