Liu Zi-Qi, Wang Yi, Wang Xiu, Peng Na, Yang Shan-Shan, Shao Hui-Hui, Jiao Xiao-Lin, Gao Wei-Wei
Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing 100193, China.
Zhongguo Zhong Yao Za Zhi. 2022 Sep;47(18):4877-4885. doi: 10.19540/j.cnki.cjcmm.20220602.101.
Appropriate light intensity is favorable for the photosynthesis, biomass accumulation, key enzyme activity, and secondary metabolite synthesis of medicinal plants. This study aims to explore the influence of light intensity on growth and quality of Panax quinquefolius. To be specific, sand culture experiment was carried out in a greenhouse under the light intensity of 40, 80, 120, and 160 μmol·m(-2)·s(-1), respectively. The growth indexes, photosynthetic characteristics, content of 6 ginsenosides of the 3-year-old P. quinquefolius were determined, and the expression of ginsenoside synthesis-related enzyme genes in leaves, main roots, and fibrous roots was determined. The results showed that the P. quinquefolius growing at 80 μmol·m(-2)·s(-1) light intensity had the most biomass and the highest net photosynthetic rate. The total biomass of P. quinquefolius treated with 120 μmol·m(-2)·s(-1) light intensity was slightly lower than that with 80 μmol·m(-2)·s(-1). The root-to-shoot ratio in the treatment with 120 μmol·m(-2)·s(-1) light intensity was up to 6.86, higher than those in other treatments(P<0.05),and the ginsenoside content in both aboveground and underground parts of P. quinquefolius in this treatment was the highest, which was possibly associated with the high expression of farnesylpyrophosphate synthase(FPS), squalene synthase(SQS), squalene epoxidase(SQE), oxidosqualene cyclase(OSC), dammarenediol-Ⅱ synthase(DS), and P450 genes in leaves and SQE and DS genes in main roots. In addition, light intensities of 120 and 160 μmol·m(-2)·s(-1) could promote PPD-type ginsenoside synthesis in leaves by triggering up-regulation of the expression of upstream ginsenoside synthesis genes. The decrease in underground biomass accumulation of the P. quinquefolius grown under weak light(40 μmol·m(-2)·s(-1)) and strong light(160 μmol·m(-2)·s(-1)) was possibly attributed to the low net photosynthetic rate, stomatal conductance, and transpiration rate in leaves. In the meantime, the low expression of SQS, SQE, OSC, and DS genes in the main roots might led to the decrease in ginsenoside content. However, there was no significant correlation between the ginsenoside content and the expression of synthesis-related genes in the fibrous roots of P. quinquefolius. Therefore, the light intensity of 80 and 120 μmol·m(-2)·s(-1) is beneficial to improving yield and quality of P. quinquefolius. The above findings contributed to a theoretical basis for reasonable shading in P. quinquefolius cultivation, which is of great significance for improving the yield and quality of P. quinquefolius through light regulation.
适宜的光照强度有利于药用植物的光合作用、生物量积累、关键酶活性及次生代谢产物合成。本研究旨在探讨光照强度对西洋参生长和品质的影响。具体而言，分别在温室中进行了光照强度为40、80、120和160 μmol·m⁻²·s⁻¹的砂培试验。测定了3年生西洋参的生长指标、光合特性、6种人参皂苷含量，并测定了叶片、主根和须根中人参皂苷合成相关酶基因的表达。结果表明，生长在80 μmol·m⁻²·s⁻¹光照强度下的西洋参生物量最大，净光合速率最高。光照强度为120 μmol·m⁻²·s⁻¹处理的西洋参总生物量略低于80 μmol·m⁻²·s⁻¹处理的。光照强度为120 μmol·m⁻²·s⁻¹处理的根冠比高达6.86，高于其他处理（P＜0.05），该处理西洋参地上和地下部分的人参皂苷含量均最高，这可能与叶片中法尼基焦磷酸合酶（FPS）、鲨烯合酶（SQS）、鲨烯环氧酶（SQE）、氧化鲨烯环化酶（OSC）、达玛烯二醇-II合酶（DS）和P450基因以及主根中SQE和DS基因的高表达有关。此外，120和160 μmol·m⁻²·s⁻¹的光照强度可通过触发上游人参皂苷合成基因表达上调来促进叶片中PPD型人参皂苷的合成。弱光（40 μmol·m⁻²·s⁻¹）和强光（160 μmol·m⁻²·s⁻¹）下生长的西洋参地下生物量积累减少可能归因于叶片净光合速率、气孔导度和蒸腾速率较低。同时，主根中SQS、SQE、OSC和DS基因的低表达可能导致人参皂苷含量降低。然而，西洋参须根中人参皂苷含量与合成相关基因的表达之间无显著相关性。因此，80和120 μmol·m⁻²·s⁻¹的光照强度有利于提高西洋参的产量和品质。上述研究结果为西洋参栽培中合理遮荫提供了理论依据，对于通过光照调控提高西洋参的产量和品质具有重要意义。
