光强对无瓣海桑幼苗的生长和光合特性的影响

根据实地测定人工无瓣海桑红树林不同环境下的光照强度,研究了不同光强环境对无瓣海桑幼苗的生长和光合特性的影响.结果表明:随着光照强度的降低,无瓣海桑幼苗的生长和光合特性指标水平均呈下降趋势,且不同光强处理间差异显著.在光照强度为全光照的80％和40％时,幼苗的各项生长指标下降,长势较全光照环境下的幼苗差;在荫蔽初期(2～4个月),弱光环境对幼苗的茎高、叶面积和叶片长宽比的增加有促进作用,随着荫蔽时间的延长,则产生抑制作用,不利于幼苗的生长;当光强达全光照的20％时,幼苗生长极为缓慢.在荫蔽处理180 d时,Sa80、Sa40、Sa20的幼苗死亡率分别为42％、70％、100％;在弱光环境下,无瓣海桑幼苗根、茎、叶的生物量分别下降了90％、80％、91％;随着环境光强水平的下降,无瓣海桑幼苗叶片的叶绿素含量、净光合速率等生理参数均呈下降趋势,各处理间差异显著.试验说明光强不足是造成无瓣海桑幼苗生长和光合水平低下及死亡率较高的主要原因,并对无瓣海桑幼苗的天然更新与自然扩散和人工造林技术进行了讨论.

Effect of Light Intensity on Growth and Photosynthetic Properties of Sonnerratia apetala Seedling

Growth and photosynthetic properties of Sonnerratia apetala seedlings were studied under different light intensity environments according to light intensity of Sonnerratia apetala in field.The results indicated that with the light intensity lessening,the trend of growth and photosynthetic properties of Sonnerratia apetala seedlings decreased.The difference of different treatments was significant.When the light intensity was 80% and 40% of full light,the growth of seedlings became worse,they grow worse than that of full light.The weak light environment was beneficial to stem height,leaf area and ratio of length to width of lamina only in initial shading stage(2 to 4 months),but with the shading time prolonging,the growth of seedlings appeared to the trend of decline.The growth of seedlings were restricted seriously in initial shading stage when the light intensity was 20%.The death rate of seedlings of Sa80,Sa40 and Sa20 in shading treatment 180 days were 42%,70% and 100%,respectively.Biomass of root,stem and leaf were decreased by about 90%,80% and 91% in weak light intensity environment.With the light intensity lessening,the trends of physiology parameters such as chlorophyll contents,net photosynthetic rate decreased,the difference among them was significant.Therefore,weak light intensity environment was the main reason for lower growth rate,lower photosynthetic rate and higher death rate of Sonnerratia apetala seedlings.In addition,the natural regeneration and diffusion and the artificial forestation technique of Sonnerratia apetala seedlings were discussed.