Abstract
Strigolactone is a newly discovered type of plant hormone that has multiple roles in modulating plant responses to abiotic stress. Herein, we aimed to investigate the effects of exogenous GR24 (a synthetic analogue of strigolactone) on plant growth, photosynthetic characteristics, carbohydrate levels, endogenous strigolactone content and antioxidant metabolism in cucumber seedlings under low light stress. The results showed that the application of 10 μM GR24 can increase the photosynthetic efficiency and plant biomass of low light-stressed cucumber seedlings. GR24 increased the accumulation of carbohydrates and the synthesis of sucrose-related enzyme activities, enhanced antioxidant enzyme activities and antioxidant substance contents, and reduced the levels of H2O2 and MDA in cucumber seedlings under low light stress. These results indicate that exogenous GR24 might alleviate low light stress-induced growth inhibition by regulating the assimilation of carbon and antioxidants and endogenous strigolactone contents, thereby enhancing the tolerance of cucumber seedlings to low light stress.
Highlights
Cucumber (Cucumis sativus L.) is an important vegetable crop
Exogenous application of GR24 significantly improved the adverse effects of low light stress on the inhibition of plant growth
Studies have revealed that MAX1, MAX3 and MAX4 gene-encoded enzymes are the key substances of the strigolactone synthesis pathway, and the content of endogenous strigolactone in the mutant is reduced, while the MAX2 gene-encoded leucine-rich repeat sequence Steady-state fluorescence yield (Fs)-box protein can recognize the substrate to promote the signal transduction of strigolactone
Summary
In northern China, low light is one of the main environmental factors that affects greenhouse cultivation in winter and spring. Several study results have shown that low light stress induces growth inhibition that might be related to a variety of physiological dysfunctions, including reduced photosynthetic efficiency, inhibition of biological carbon fixation, accumulation of reactive oxygen species (ROS) and membrane lipid peroxidation [1,2,3,4,5,6]. Low light stress often causes oxidative damage, which is manifested in the generation of ROS. Several antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), are activated in stressed plants to scavenge ROS [7, 8]. Plants acclimated to low light showed lower biomass production and higher membrane lipid peroxidation [9]
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