Direct measurement of paraquat in leaf protoplasts indicates vacuolar paraquat sequestration as a resistance mechanism in Lolium rigidum

Sequestration of paraquat away from its target site in the chloroplast has been proposed as a mechanism of paraquat resistance. However, no consensus has been reached as to where paraquat is sequestered. This study quantifies paraquat in leaf protoplasts of paraquat resistant (R) and susceptible (S) Lolium rigidum. Intact protoplasts were prepared from plants treated with commercial dose of paraquat for 2 h. Paraquat absorbed by the leaf protoplasts was determined by light absorption of reduced paraquat following concentration and purification using a cation-exchange resin. Leaf protoplasts from treated paraquat resistant plants contained 2- to 3-fold more paraquat than leaf protoplasts isolated from susceptible plants. Since paraquat is not metabolised in L. rigidum and paraquat readily enters chloroplasts of both R and S plants, this greater amount of paraquat in leaf protoplasts of R plant must be kept away from the target site (chloroplast). This result indicates that paraquat resistance in L. rigidum is associated with a cytoplasmic mechanism, most likely a greater rate of vacuolar sequestration.

Pesticide Biochemistry and Physiology, 98.1: 104-109

Keywords: Leaf protoplasts, Lolium rigidum, Paraquat resistance, Vacuolar sequestration

Publication Year: 2010

Authors: Q Tu, S Huang, S Powles

Download PDF
Get access to short and sharp insights into the world of more crop, fewer weeds with AHRI Insight.
Subscribe Now