Effects of bensulfuron-methyl residue on photosynthesis and chlorophyll fluorescence in leaves of cucumber seedlings.

Lanlan Sun,Chuantao Lu,Hongdan Hao,Hongle Xu,Wangcang Su,Shiheng An,Renhai Wu,Haitao Shi

doi:10.1371/journal.pone.0215486

Abstract

A potted soil experiment was conducted to investigate the effects of bensulfuron-methyl (BSM) residue on the growth and photosynthesis of seedlings of a local cucumber variety (Xia Feng No.1). When the residue of bensulfuron-methyl in soil exceeded 50μg kg-1, it significantly inhibited the growth of cucumber, chlorophyll content and photosynthetic capacity of cucumber. BSM treatment caused significant decreases in the biomass, chlorophyll content, net photosynthesis rate, stomatal conductance, and transpiration rate, photosystem II (PSII) maximum quantum yield, actual quantum yield, photochemical quenching coefficient, and electron transport rate in cucumber seedlings, but increased the minimal fluorescence yield and dark respiration rate. Moreover, comparisons of the patterns of absorbed light energy partitioning revealed that the fractions of excess and thermally dissipated energy increased with rising concentrations of the BSM residue, but the fraction of PSII photochemistry declined. The BSM residues caused reversible destruction in the PSII reaction centers and decreased the proportion of available excitation energy used in PSII photochemistry. The results suggested that rice or wheat fields sprayed with BSM will not be suitable for planting cucumbers in succession or rotation.

Highlights

Herbicides are necessary for weed control in intensive crop production, and play an important role in modernization of agriculture
The growth of cucumber seedlings was greatly inhibited by the BSM residue
The shoot length, root length, shoot dry mass (SDM), root dry mass (RDM), and total dry mass (TDM) of cucumber seedlings decreased significantly with the presence of the BSM residue, and the degree of decrease was directly related to the BSM concentration added to soil

Summary

Introduction

Herbicides are necessary for weed control in intensive crop production, and play an important role in modernization of agriculture. Bensulfuron-methyl (BSM) has been used since the 1970s and now is widely used in paddy fields in the world. In China, BSM was first used in paddy fields to control sedge and broadleaf weeds, and it is used to control broadleaf weeds in wheat fields [1]. BSM is principally absorbed by roots and leaves, and can inhibit acetolactate synthase and the biosynthesis of branched-chain amino acids[2]. The herbicide shows high selectivity and has been used extensively for many years.

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