<![CDATA[By Yiman Li et al.
- Drought stress decreased the cucumber root biomass and hydraulic conductivity, the contents of IAA, ZR, and GA, while increased the ABA content, and decreased the transcript levels of aquaporin-related genes CsPIP2-5 and CsPIP2-7.
- CO2 enrichment increased the GA content and the transcript levels of CsPIP2-7, and decreased ABA content and the transcript levels of CsPIP2-4 of cucumber roots under moderate drought stress.
- CO2 enrichment increased the root biomass and improved root hydraulic conductivity and enhanced water absorption and transport capability of cucumber seedlings under drought stress, thereby alleviated the impact of drought stress on cucumber seedlings.
The coordinated effects of CO2 enrichment and drought stress on cucumber leaves have attracted increasing research attention, but few studies have investigated the effects of CO2 enrichment on the root system under drought stress. So we analyzed the morphological parameters, hydraulic conductivity, aquaporin-related gene expression, and endogenous phytohormone contents in roots of cucumber seedlings cultured under different CO2 concentrations (approximately 400 and 800 ± 40 μmol mol−1) and drought stresses simulated by polyethylene glycol 6000 (0%, 5%, and 10%). The results showed that under drought stress, regardless of the CO2 concentration, the root biomass and hydraulic conductivity decreased, the contents of auxin (IAA), zeatin nucleoside (ZR), and gibberellin (GA) decreased, the abscisic acid (ABA) content and the transcript levels of the aquaporin-related genes CsPIP2-4 increased, and the transcript levels of the aquaporin-related genes CsPIP2-5 and CsPIP2-7 decreased compared with no drought stress. Under moderate drought stress, CO2 enrichment decreased ABA content and the transcript level of CsPIP2-4, increased root biomass and GA content and the transcript level of CsPIP2-7, improved contribution rate of cell-to-cell water transport (mediated by aquaporins) and roots hydraulic conductivity. In summary, drought stress changed the water transport capacity of the roots and inhibited the growth of cucumber seedlings. CO2 enrichment regulated phytohormone contents and aquaporin-related gene expression, maintained the normal contribution rate of cell-to-cell water transport, and improved the root biomass and hydraulic conductivity, thereby alleviated the negative effects of drought stress on cucumber seedlings.
This (paywalled) article appeared on the Plant Physiology and Biochemistry website at https://www.sciencedirect.com/science/article/abs/pii/S0981942820302060