Exogenous silicon alleviates drought stress in maize by improving growth, photosynthetic and antioxidant metabolism

Extreme dry weather caused by global climate change will reduce the growth and yield of plant crops. Silicon (Si) can improve plant growth and the resistance to various stresses. However, its effects on maize drought stress of the jointing and tasseling stages are unclear in the field. Therefore, the present study was carried out to investigate the effect of growth, photosynthetic and antioxidant metabolism on maize under moderate and severe drought stress with or without Si application (5, 15, 25 g.L-1) in the large farmland moisture control test field. Drought stress down-regulated plant height growth rate (25.80% similar to 39.11%), shoot dry weight (40.42% similar to 68.97%), root dry weight (31.34% similar to 57.96%) and yield (14.51% similar to 36.52%) in the both stages, respectively. With the increase of drought stress, actual photochemical efficiency of PSII (phi PSII), maximum photochemical efficiency of PSII (Fv/Fm) and photochemical quenching (qP) decreased at different degrees while the nonphotochemical quenching (NPQ) increased. One-to-twofold increase was observed in the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in the drought-stressed conditions. Exogenous Si alleviated drought stress to a certain extent of damage, enhanced plant growth, photosynthetic pigment contents, chlorophyll fluorescence parameters, gas exchange parameters, photosynthetic enzymes activity, the stomatal size and stomatal aperture, inhibited the increase in the superoxide free radical ion (O-2(center dot-)) production rate, hydrogen peroxide (H2O2), malondialdehyde (MDA) and electrolyte leakage (EL), and further increased the key antioxidant enzymes activities and the osmotic regulatory substance contents. The activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), and the contents of ascorbate (AsA) and glutathione (GSH) increased, and the contents of dehydroascorbate (DHA) and oxidized glutathione (GSSG) declined by Si application in both stages. Therefore, exogenous Si could decrease maize oxidative stress response in drought-stressed by strengthening the antioxidant defense system and photosynthetic metabolism, improving the AsA-GSH cycle, increasing osmotic substance contents, as well as playing a vital role in improving the drought resistance of maize. Overall, the external use of Si ameliorated growth, photosynthetic and antioxidant metabolism under drought stress.

Automated summary

Extreme dry weather caused by global climate change will reduce the growth and yield of plant crops. Silicon (Si) can improve plant growth and the resistance to various stresses. This study investigated the effects of moderate and severe drought stress on the growth, photosynthetic and antioxidant metabolism of maize, and explored the role of Si application in mitigating the damages caused by drought stress. The results showed that drought stress significantly reduced plant height, shoot and root dry weight, and yield of maize. It also affected the efficiency of photosynthetic processes and led to the production of harmful free radicals. However, the application of Si alleviated the negative effects of drought stress by enhancing plant growth, photosynthetic efficiency, antioxidant defense system, and osmotic regulation. These findings suggest that Si can play a vital role in improving the drought resistance of maize.