The Combination Treatment With Urea and Mesosulfuron-methyl on the Photosynthesis and Yield of Perilla frutescens( L. ) Britt.

Perilla with six leaves was exposed to combination treatment with urea( 0,1,2,4 and 8 g·L- 1) and mesosulfuron-methyl( 0,0. 175,0. 35,0. 7 and 1. 4 m L·L- 1) of different concentration to confirm the best treatment style. Effect of combination treatment on photosynthetic index and seed yield of Perilla frutescens( L.) Britt. Was investigatea by using the randomized block design experiment. Results showed that the chlorophyll content index( CCI)significantly,and photosynthetic rate( Pn) and stomatal conductance( Gs) were reduced at different levels. While the intercellular CO2concentration( Ci) was increased under the mesosulfuron-methyl treatments. It suggested that mesosulfuron-methyl significantly decrease the photosynthesis. The result also show that mesosulfuron-methyl significantly decreased maximum PSII photochemical efficiency, effective quantum yield of photochemical energy conversion in PSII,PSII potential activity and photochemical quenching of variable Chl fluorescence; and decreased non-photochemical Chl fluorescence quenching. It was indicated that mesosulfuron-methyl impaired PSII and blocked the electron transport in light reaction,treatment with urea of moderate concentration( 1 to 4 g·L- 1) could improve the negative effect contributed by mesosulfuron-methyl alone,while high concentration( 8 g·L- 1) could aggravate this effect. The photosynthesis and PSII photochemical efficiency were improved when treated by 4 g·L- 1urea first and then by 0. 7 m L·L- 1mesosulfuron-methyl. This combination of urea and mesosulfuron-methyl was the best treatment,this study could provide a theoretical basis for the balance of fertilization,weeding,security and high yield in Perilla field.