光强对喜树幼苗生长及喜树碱含量的影响

喜树(Camptotheca acuminata)是我国特有树种,其次生代谢产物喜树碱具有抗肿瘤活性,但喜树碱的生物合成受环境因子的影响较大。笔者在人工气候室中,采用盆栽试验方法,研究了不同光合有效辐射(300、500、800 μmol/(m²·s),对应记为L1、L2、L3)条件下,喜树当年生幼苗的生长及喜树碱生物合成和积累的差异。结果表明,L1条件下,喜树幼苗的苗高增量和地径增量最高。随着光强的增强,根冠比先升高后降低,而生物量总体呈下降趋势。L3条件促进了喜树叶片中可溶性糖及可溶性蛋白质的积累,L1与L3条件则提高了TDC活性。在L1条件下,喜树碱含量和单株产量最高,表明弱光条件有利于喜树碱的合成与积累。

Effects of light intensity on the growth of Camptotheca acuminata seedlings and camptothecin contents

Camptotheca acuminata, a rapid growing tree indigenous to south China, which can produce a kind of anticancer secondary metabolite, camptothecin(CPT). CPT is classified as a modified monoterpenoidindole alkaloid that has attracted great attention for its significant role in antitumor activity. It is presumed that CPT is one of the defence compounds of C.acuminata, but the contents of CPT are usually very low. Previous reports have shown that environmental factors such as light intensity can affect plant growth and metabolite synthesis. To enhance CPT yield in C. acuminata, we observed the effects of light intensity on CPT production in the leaves of C. acuminata. We use three levels of light intensity, namely L1 300, L2 500, L3 800 μmol/(m²·s). The samples were collected from the third to fifth leave from the seedling top at the 7, 14, 21 and 28 days after treatment. The results were shown as follows. At L1, there were great increments in the seedling height and caliper. With the increase of light intensity, the root cap ratio increased in the beginning and then decreased, while the biomass generally showed a decreasing trend. The seedlings possessed the highest soluble sugar and soluble protein accumulation at L3. Both L1 and L3 had positive effect on TDC activities, and in the meantime, there was a great enhancement in CPT concentration and yield per plant at L1. This may have important implications for the production of the antitumor drug CPT in plantations at an industrial scale.