Roots and rhizomes of Rubia yunnanensis are important Chinese medicine materials with significant anti-tumor activity, which is mainly obtained from wild resources. There is an urgent need to develop the production practice for the cultivation of R. yunnanensis. The current study was performed to investigate the changes in the photosynthetic pigment content, photosynthetic characteristics, chlorophyll fluorescence parameters, biomass production, and secondary metabolites Rubiaceae-type cyclopeptides (RAs) contents in roots and rhizomes by drought and re-watering in R. yunnanensis grown in four water conditions: well-watered control (C), moderate drought (MD), severe drought (SD), and re-watering after moderate drought (RMD). The results indicated that compared with the control, drought stresses (MD and SD) significantly decreased photosynthetic pigments and impaired photochemical efficiency, as revealed by the reductions of maximum potential PSII efficiency (Fv/Fm), effective quantum yield of photochemical energy conversion (Yield) and electron transport rate (ETR), etc., resulting in limited photosynthetic capacity, and hence reduced biomass accumulation and RAs contents and yields in roots and rhizomes. The RMD plants could produce compensation effect and their photosynthetic ability recovered to control level; they showed the comparable dry biomass of roots and rhizomes and higher contents and yields of RAs compared with the control. This implied that moderate drought-induced injury in R. yunnanensis was reversible. These results reinforce the importance of water management and recommend the re-water operation for the cultivation of R. yunnanensis.

云南茜草的根和根茎是重要的中药材，具有显着的抗肿瘤活性，其主要来源是野生资源。迫切需要发展生产云南松的生产实践。本研究旨在调查干旱和再浇水对根和根茎中根和根茎的光合色素含量，光合特性，叶绿素荧光参数，生物量产生和次生代谢产物茜草类环肽（RA）含量的影响。在四种水分条件下生长：适度灌溉（C），中度干旱（MD），重度干旱（SD）和中度干旱后补水（RMD）。结果表明，与对照相比，干旱胁迫（MD和SD）显着降低了光合色素的含量和光化学效率的降低，这表现为最大潜在PSII效率（Fv / Fm）的降低，光化学能转化的有效量子产率的降低（Yield ）和电子传输速率（ETR）等，导致光合能力受到限制，从而降低了根和根茎中的生物量积累以及RA含量和产量。RMD植物可以产生补偿作用，其光合能力恢复到控制水平。他们显示了与对照相比，根和根茎的干燥生物量相当，RA的含量和产量更高。这意味着中度干旱造成的伤害云南R.是可逆的。这些结果加强了水管理的重要性，并建议对云南松的栽培进行复水操作。