光照强度对西藏虎头兰幼苗生长及光合特性的影响

Effects of Light Intensity on the Growth and Photosynthetic Characteristics of Cymbidium tracyanum L.Castle Seedlings

关键词:  西藏虎头兰|光照强度|净光合速率|光响应曲线|日变化

Key words:  Cymbidium tracyanum L.Castle|light intensity|net photosynthetic rate|light response curve|diurnal variation

摘要:

探究西藏虎头兰(Cymbidium tracyanum L.Castle)幼苗对不同光照强度的适应性，明确其生长的适宜光照强度，为该物种资源保育及驯化提供科学依据。以苗龄为2 a的西藏虎头兰为研究对象，测定了不同光照强度下(8%、20%、45%、100%全光照)西藏虎头兰的生长状况、叶绿素含量和光合参数等的变化。结果表明：西藏虎头兰在20%光照强度下长势最好，其株高、分株基径、冠幅和最大叶长最大。随着光照强度的升高，西藏虎头兰叶片的叶绿素a (Chl a)、叶绿素b (Chl b)、类胡萝卜素(Car)和叶绿素(a+b)[Chl (a+b)]含量均显著降低，Car/Chl(a+b)升高，Chl a/ Chl b无明显变化。8%和20%光照强度下西藏虎头兰的净光合速率(P_n)呈现“单峰”曲线，45%光照强度下呈现“双峰”曲线；日均P_n大小表现为20%光照强度(0.78 μmol·m^-2·s^-1)＞8%光照强度(0.55 μmol·m^-2·s^-1)＞45%光照强度(0.23 μmol·m^-2·s^-1)。20%光照强度下西藏虎头兰的光补偿点(LCP,8.86 μmol·m^-2·s^-1)最低,光饱和点(LSP,607.67 μmol·m^-2·s^-1)、表观量子效率(AQY,0.041)和最大净光合速率(P_max,2.91 μmol·m^-2·s^-1)最高。本研究中,西藏虎头兰在20%光照强度下植株长势最好、光合作用能力最强，因此在进行引种栽培时应提供适当的光照，有助于其生长。

Abstract:

The adaptability of Cymbidium tracyanum L.Castle seedlings to different light intensities was explored to determine the suitable light intensities for their growth,so as to provide scientific basis for resource conservation and domestication of this species. Taking the 2-year-old C.tracyanum L.Castle as the research object,the growth status,chlorophyll content and photosynthetic parameters of C.tracyanum L.Castle under different light intensities (8%,20%,45%,100% full light) were measured. The results showed that the growth of C.tracyanum L.Castle was the best under 20% light intensity,and its plant height,ramet base diameter,crown width and maximum leaf length were the largest. With the increase of light intensity,the contents of Chl a,Chl b,Chl (a+b) and Car in the leaves of C.tracyanum L.Castle significantly decreased,while Car/Chl (a+b) increased,Chl a/b had no significant change. The net photosynthetic rate (P_n) of C.tracyanum L.Castle showed a 'single peak' curve under 8% and 20% light intensities,and under 45% light intensity,it showed 'double peak' curve. The daily average P_n size was 20% light intensity (0.78 μmol·m^-2·s^-1)＞8% light intensity (0.55 μmol·m^-2·s^-1)＞45% light intensity (0.23 μmol·m^-2·s^-1). Under 20% light intensity,the light compensation point (LCP,8.86 μmol·m^-2·s^-1) was the lowest,the light saturation point (LSP,607.67 μmol·m^-2·s^-1),the apparent quantum yield (AQY,0.041 μmol·m^-2·s^-1) and the maximum net photosynthetic rate (P_max,2.91 μmol·m^-2·s^-1) were the highest. In this study,the plants of C.tracyanum L.Castle had the best growth and the strongest photosynthesis ability under 20% light intensity. Therefore,appropriate light should be provided to help its growth during the introduction and cultivation.