Abstract
Waterlogging stress is one of the most important abiotic stresses limiting sorghum growth and development. Consequently, the responses of sorghum to waterlogging must be monitored and studied. This study investigated changes in the leaf water status, xylem exudation rate, leaf anatomical structure, leaf temperature and photosynthetic performance. Waterlogging-tolerant (Jinuoliang 01, abbreviated JN01) and waterlogging-sensitive (Jinza 31, abbreviated JZ31) sorghum cultivars were planted in pots. The experiment was carried out using a split block design with three replications. Waterlogging stress was imposed at the sorghum five-leaf stage. The leaf free water content (FWC) and relative water content (RWC) decreased under the waterlogged condition. The leaf thickness was thinner under the waterlogged condition, and the main changes occurred in the upper epidermal and mesophyll cells. Gas exchange parameters and the xylem exudation rate were also restrained by waterlogging; however, greater responses of these parameters were observed in JZ31. JZ31 had a higher leaf-air temperature difference (ΔT) than JN01. We found that changes in ΔT were always consistent with changes in the RWC and the gas exchange parameters. ΔT was significantly associated with the leaf RWC, photosynthetic rate (Pn) and transpiration rate (Tr). The results suggest that ΔT may be an indicator reflecting the water status in leaves and can be used to evaluate the tolerance of sorghum to waterlogging.
Highlights
Waterlogging is becoming an increasingly important abiotic stress that seriously restricts crop growth [1]
The plant height of both cultivars was significantly restrained by the waterlogging stress; the plant heights of Jinuoliang 01 (JN01) and Jinza 31 (JZ31) were decreased by 16.27% and 30.42%, respectively, compared to those of the CK groups
Waterlogging resulted in a reduction in the relative water content (RWC) in both cultivars compared with that of the CK groups; the RWC of waterlogged JN01 and JZ31 was reduced by 2.64% and 7.57%, respectively
Summary
Waterlogging is becoming an increasingly important abiotic stress that seriously restricts crop growth [1]. 12% of cropping areas suffer from waterlogging stress every year, and these areas are increasing [2]. Because sorghum has strong resistance to unfavourable conditions, it usually is grown in marginal areas, such as low-lying regions and flooded areas with poor drainage [3]; sorghum is frequently affected by waterlogging stress due to short-term heavy rainfall. To cope with waterlogging stress, the responses of plants to this stress need to be monitored in an accurate and timely manner to potentially mitigate the adverse effects of waterlogging on sorghum production
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