Abstract
BackgroundWater deficiency is likely to become more frequent and intense as a result of global climate change, which may severely impact agricultural production in the world. The positive effects of melatonin (MEL) on alleviation drought or osmotic stress-induced water deficiency in plants has been well reported. However, the underlying mechanism of MEL on the detailed process of plant water uptake and transport under water deficiency condition remains largely unknown.ResultsApplication of 1 μM MEL led to enhanced tolerance to water deficiency stress in maize seedlings, as evidenced by maintaining the higher photosynthetic parameters, leaf water status and plant transpiration rate. The relatively higher whole-plant hydraulic conductance (Kplant) and root hydraulic conductance (Lpr) in MEL-treated seedlings suggest that exogenous MEL alleviated water deficiency stress by promoting root water absorption. HgCl2 (aquaporin inhibitor) treatment inhibit the transpiration rate in MEL-treated plants greater than those of MEL-untreated; after recovery by dithiothreitol (DTT, anti-inhibitor), the transpiration rate in MEL-treated plants increased much higher than those of untreated plants. Moreover, under water deficiency, the transcription level of aquaporin genes was up-regulated by MEL application, and the H2O2 was less accumulated in MEL-treated root.ConclusionsExogenous MEL promoted aquaporin activity, which contributed to the maintaining of Lpr and Kplant under short-term water deficiency. The increased water uptake and transport lead to improved water status and thus increased tolerance to PEG-induced short-term water deficiency in maize seedlings.
Highlights
Water deficiency is likely to become more frequent and intense as a result of global climate change, which may severely impact agricultural production in the world
The transpiration rate fluctuated slightly at the beginning of the treatment and the significant difference began to occur after three hours of polyethylene glycol (PEG) treatment (11:00 a.m.), at which time point the whole-plant transpiration rate was higher in MEL-treated seedlings than that untreated, and this tendency was continued during the subsequent observation period (Fig. 2)
The Whole-plant hydraulic conductance (Kplant) was 58% higher in MEL-treated seedlings than that of untreated under water deficiency condition (Fig. 4), indicating that MEL could contribute to high water uptake capability under this condition
Summary
Water deficiency is likely to become more frequent and intense as a result of global climate change, which may severely impact agricultural production in the world. The positive effects of melatonin (MEL) on alleviation drought or osmotic stress-induced water deficiency in plants has been well reported. Drought or osmotic stress-induced water deficiency is one of the most severe abiotic stresses in agricultural production, and MEL has been widely reported to improve plant tolerance to water deficiency stress in various plants [7, 10,11,12,13]. Numbers of physiological and biochemical processes have been reported to be involved in MEL-mediated plant water deficiency stress response. MEL-mediated scavenging of reactive oxygen species by increasing antioxidant capacity has been proved to be an important mechanism for improving plant tolerance to water deficiency stress [12, 14]. Rhizosphere application of MEL (10 μM) was found to promote the nitrogen metabolism and proline homeostasis in drought-stressed alfalfa, and lead to a higher level of chlorophyll fluorescence and stomatal conductance [6]
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