4.3 | Abiotic stress and inter-root antioxidant
The accumulation of active oxygen free radicals in the rhizosphere of plants causes oxidative damage to the cell membrane system of the root tip and leads to a series of physiological and biochemical changes in the root’s absorptive function (Mittler et al., 2022). The results of this study showed that S. miltiorrhiza significantly down-regulated the activity of S-CAT secreted by the root under N, DN, and TN stresses. Under the synergistic stresses of three and four factors, S. miltiorrhiza has tended to up-regulate the activity of root-secreted S-CAT. This is similar to the effect of nitrogen inhibiting the secretion of enzymes in maize roots (Liang et al., 2016) but different from the effect of drought stress stimulating the secretion of antioxidant substances in maize roots (Song et al., 2012). Overall, N, DN, and TN stresses can cause active oxygen hazards in the rhizosphere, affecting the uptake and transport of rhizosphere nutrients.