Effects of Uniconazole on Leaves Photosynthesis, Root Distribution and Yield of Mung Bean (Vigna radiata)

Uniconazole was a plant growth retardant with effect of regulating plant growth and development, however, there were very few studies on its application to mung bean. In this study, the leaves of mung bean were sprayed with uniconazole solution (30 mg·L−1) at V3 stage. Photosynthetic indicators, root distribution were measured at R5 and R6, and yield and components were measured at maturity. Uniconazole increased Gs (stomatal conductance) and Tr (transpiration rate) at R5 and R6, Pn (net photosynthesis rate) at R6, and SPAD value at R5. The SPAD value at R5 had the greatest correlation with yield with a correlation coefficient of 0.684. According to distribution pattern of decreasing root length density from top to bottom, large amounts of water absorbed by the roots was more likely to come from the upper soil layer, especially 0–20 cm soil layer. As the depth of soil layer increased, the proportion of root dry weight in different soil layers were 69, 14, 9, 5 and 3%, respectively. Uniconazole effectively reduced root proportion in 0–20 cm soil layer and increased root proportion in 20–60 cm soil layer. Root dry weight density in 20–40 cm soil layer and yield were significantly positively correlated (r = 0.938* at R5, r = 0.891* at R6). In addition, uniconazole increased hundred grain weight and yield, reduced pods number per plant and seeds number per pod. Based on the results, this study can provide guidance for mung bean production and high-yield breeding in the future.