青藏高原53种菊科植物种子中碳、氮、磷含量与种子大小和海拔的关系

以青藏高原东北缘广泛分布的53种常见菊科植物种子为研究材料,以重铬酸钾外加热法和流动注射分析仪测定种子中碳、氮、磷含量,探讨种子中碳、氮、磷组成及分配是否随种子大小及生境海拔高度变异,为进一步探讨植物对环境变化的响应提供理论依据。结果表明:(1)53种菊科植物种子大小差异显著,且随海拔升高种子有变小的趋势。(2)53种菊科植物种子中C、N、P含量及其比值差异显著,不同海拔梯度的物种种子中C、N、P含量及其比值差异不显著,但C、N含量有随海拔升高增加的趋势,而P含量有随海拔升高降低的趋势。(3)种子大小变异并不影响其C的相对含量,但N、P含量与种子大小呈显著负相关关系,C/N、C/P、N/P与种子大小呈显著正相关关系,即种子越小,种子中N、P相对含量越高。因此,高海拔条件下,种子中积聚相对较多的C、N可以为其生长发育初期提供较高的能量及较多的蛋白质合成,从而增强幼苗抵御恶劣环境条件的能力,提高幼苗的存活率;较小种子中相对较高的N、P含量可以为早期幼苗提供足够的蛋白质和核糖体,帮助幼苗快速生长,从而克服其产生较小幼苗的劣势。研究表明,植物种子中C、N、P含量随种子大小及海拔的变异趋势是一种适应性选择的结果。

Effect of Seed Size and Altitude on the C,N,P Contents of 53 Compositae Plant Seeds on the Northeastern Qinghai-Tibet Plateau

In this study,we discussed the effect of seed size and altitude on the C,N,P contents of 53 Compositae plant seeds on the northeastern Qinghai-Tibet Plateau,and provided theoretical evidence for discussing the response of plants to environmental change.Seed size was defined by the average of three samples with hundred seeds,and element content of seed was measured with K₂Cr₂O₇ external heating method and flow injection analyzer.The results showed that:(1)There was significant difference in seed size of 53 Compositae plants,and a trend that seed size decreased with increasing altitude;(2)There was no significant difference in the C,N,P contents of seeds and their ratio among altitudes.However,there was a trend that the C,N content of seeds increased and the P content of seeds decreased with increasing altitude;(3)The C contents of seed did not change with seed size variation.While the N and P contents of seeds had significant negative correlation with seed size,and C/N,C/P and N/P ratios have significant positive correlations with seed size.The seeds with more relative contents of N and P are going with smaller seed size.This study suggested that the more accumulation of C and N in seeds could offer more energy and synthesis of proteins in the earlier stages of plants,and then would improve the ability of seedlings to resist harsh environment and enhanced the survival rate;the more contents of N and P in smaller seeds could offer enough proteins and ribosomes for the earlier growth of seedlings and help them to grow fast,and then would overcome the disadvantages due to smaller size.Thus,it is an adaptive selection that contents of C,N and P in seeds changed with seed size variation and altitude gradients.