Abstract:
Objectives Exogenous melatonin (melatonin, MT) is capable of increasing the stress resistance of crops. We studied the mechanism of MT on the drought resistance of wheat from the aspects of development of spike and floret.
Methods A field experiment was conducted using a multi-spike cultivar ‘Yumai 49-198’ and a large-spike cultivar ‘Zhoumai 22’ as experimental materials. Three soils were watered to 70%−80%, 60%−70%, and 50%−60% of field water capacities to simulate the treatments of normal (W1), mild and moderate drought stress (W2, and W3), respectively. Before the peak of floret degradation, the wheat under each water condition was foliar sprayed with 100 μmol/L melatonin (MT) and clear water control (CK), respectively. The development of floret and spikelet in the main stems were observed since the 3rd day of MT treatment, with frequency of every three days until the end of flowering stage, and the plant water content, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and enzyme activities were determined at the same time.
Results Compared with W1 treatment, W2 and W3 treatments reduced the total number of differentiated florets, the numbers of degenerated nodal florets and fertile florets, and the grain number per spike in both wheat cultivars, and led to a decrease in the water content of wheat plants, and an increase in the content of H2O2 and MDA in top spread leaves. MT treatment improved the quality of floret development, reduced floret degradation, increased the number of degraded nodal florets, fertile florets and grains in fruiting spikes in both cultivars, and the promotional effect on cultivar Zhoumai 22 was higher than on Yumai 49-198. MT treatment effectively reduced leaf MDA and H2O2 contents by 5.80%−15.31% and 6.83%−15.16% in Yumai 49-198, and by 6.94%−16.83% and 7.60%−17.06% in Zhoumai 22, increased the activities of SOD and CAT by 4.25%−13.39% and 4.86%−15.68% in Yumai 49-198, and by 5.62%−14.49% and 5.42%−16.50% in Zhoumai 22, respectively, and the regulatory effect on Zhoumai 22 was higher than on Yumai 49-198. MT treatment was recorded significant promotion effect on dry matter production and accumulation in spike organs, the dry matter accumulation was improved by 6.66%−11.72% in Yumai 49-198 and 8.06%−12.52% in Zhoumai 22 on the 15th day of MT treatment.
Conclusions Spraying exogenous melatonin before the peak of wheat floret degradation effectively increases the water content of top spread leaves, and thus increases the antioxidant system activity and maintains the stability of leaf cell membrane structure, alleviates drought damage to the plant and improves dry matter production for the requirement for floret development and grain setting, expressed as improved number of fertile florets and the grain number per spike.
下载: