不同光环境下大头茶幼苗蒸腾强度和生物量的变化

Transpiration and Biomass Variations of Gordonia acumenata Seedlings in Different Light Environments

大头茶(Gordonia acumenata)幼苗的蒸腾强度与光照强度、气温和叶温成正相关,而与叶水势和相对湿度成负相关;蒸腾强度日变化为单峰曲线,峰值在12:00,年变化峰值均在7月份,但由于光强原因,9—10月份蒸腾强度又有所回升,随后下降。一年(1991年3月—1992年2月)中,幼苗蒸腾强度均为全光照>部分光照(55%的全光照)>部分阴暗(33%的全光照)>阴暗(17%的全光照);从叶面积和茎枝生长来看,全光照>部分光照或部分阴暗>阴暗;然而,从全光照到阴暗,幼苗地上部分生物量分配(与自身地下部分生物量相比较)相对增加,从而,使根/冠比下降,以上特点表明,幼苗对其相应光环境具有一定的适应能力。

In Gordonia acumenata seedlings, the correlation between transpiration intensities and light intensities, air temperatures, leaf temperatures were positive, and that between transpiration intensities and relative humidities, leaf water potentials were negative. The results showed that transpiration diurnal variation was the shape of a unimodal curve with a peak value at 12 o'clock and that transpiration intensities were from lower to higher monthly, all of the intensities in various light environments reached peak value in July, owing to affected by light, the transpiration intensities increased slightly from September to Octomber, then decreased gradually. During a year (from March, 1991 to Feb, 1992), the transpiration intensities of the seedlings in different light environments appeared as follows: Full sun>Partial sun (55% of full sun) >Partial shade (33% of full sun) >Shade (17% of full sun). Seedlings in Full sun showed the best growth, which coincided with the characteristics of light-demanding tree species, however, with the change of light intensities (from Full sun to Shade), the biomass allocation of shoots increased and that of roots decreased comparatively, therefore, the root/snoot ratio decreased, which indicates that the seedlings have been improved to adapt to their corresponding light environments.