Effects of low light intensity on changes of soluble sugars, alkaloids and phytohormones in Catharanthus roseus seedlings
弱光对长春花（Catharanthus roseus）幼苗中可溶性糖、生物碱及激素含量的影响

The variations of soluble sugars, alkaloids and phytohormones contents in leaves of Catharanthus roseus seedling subjected to low light intensity (LL) and normal light (NL) condition were investigated in this paper. The purpose was to elucidate the effects of LL on soluble sugars, alkaloids and phytohormones of C. roseus and the possible roles of these physiological metabolisms played during acclimation to LL. Leafstalk and node length were significantly increased upon LL exposure, while the lower energy percent were allocated to sexual reproduction. In the first week, the concentrations of fructose (Fru), glucose (Glc) and sucrose (Suc) significantly deceased under LL from (0.62±0.01), (1.86±0.12), (0.24±0.01) mg/g FW to (0.38±0.02), (0.60±0.03), (0.17±0.02) mg/g FW, respectively. This may be related to decreased level of assimilation of leaves under LL. The accumulation of vindoline (VIN) and catharanthine (CAT) contents in leaves elevated after LL exposure up to threefold compared to control at the end of treatment. At the same time, however, the content of the anticancer compound vinblastine (VLB) generated by its precursors VIN and CAT decreased to 50% of the control. In the first two weeks, the contents of abscisic acid (ABA), gibberelline (GA3) and indole-3-acetic acid (IAA) in C. roseus leaves were enhanced. This result may be related to the rapid increasing of plant nodes and leafstalk length. In conclusion, these results indicate that the acclimations of plants to LL were positively regulated by physiological metabolisms. This may have important implications for the production of the anticancer drug VLB in plantations and greenhouses at an industrial scale.