Effects of glyphosate and paraquat on root morphology and aboveground growth of Prunus persica seedlings

Abstract

To ascertain the safety of herbicides in peach production, we examined the effects of two herbicides (glyphosate and paraquat) on vegetative growth, root structure, root-tip cell mitosis and photosynthesis in rootstock Prunus persica seedlings. The results showed that the growth of both shoot and root of the P. persica seedlings was significantly inhibited under the glyphosate treatment. Compared with the control, plant height decreased by 31.5%, total root length, root surface area, root volume and the number of root tips decreased by 39.5%, 39.5%, 49.8% and 44.6%, respectively. The paraquat treatment had no significant differences compared with the control. The mitotic index of root tip cells decreased by 38.0% and 35.9% under both herbicide treatments, respectively. The proportion of cells at metaphase against the total number of mitotic cells in the root tips was significantly reduced by glyphosate treatment compared with the control and the paraquat treatment. Root tip cells of peach were sensitive to both kinds of herbicides. The leakage of electrolytes from the cells in root tips was significantly higher than that of the control from the second day to the thirtieth day after treatments. After five days of glyphosate treatment, electrolyte leakage rate of leaves was raised, the bases of young leaves turned yellow, and spread to leaf tips, parts of which ultimately withered. Net photosynthetic rate, stomatal conductance, and transpiration rate were reduced more strongly under the glyphosate treatment than the paraquat treatment. In conclusion, both kinds of herbicides reduced cell mitotic index of root tip cells and leaf net photosynthetic rate, increased the electrolyte leakage rate of the root tip cells in P. persica seedlings. Glyphosate had a greater effect on vegetative growth and leaf photosynthesis, which could cause young leaves yellowing and leaf tips scorching.