Methiozolin is a herbicide in the isoxaline chemical family developed in 2005 for Poa annua management in turfgrass. However, the knowledge on its herbicidal action physiology is still insufficient enough. In this study, it was investigated whether or not methiozolin has a same action physiology with cinmethylin to Lemna paucicostata (LEMPA) and how the methiozolin injury is alleviated or enhanced by a supplements of various metabolites. As a results, both methiozolin and cinmethylin induced the same herbicidal symptoms to LEMPA such as a decreased proliferation, partial chlorosis in young fronds, frond stack, abnormal shape of fronds, miniaturation and root growth inhibition, and showed a similar patterns in the physiological indication of herbicidal activity. In metabolite supplmentation study, the additions of sodium oleate, geranylgeraniol, β-carotene, or α-tocopherol could almost completely lessen the phytotoxic effects of methiozolin to LEMPA. Considering these results and other reports, the primary action sites of methiozolin is likely to be fatty acid thioesterase (FAT) on the fatty acid biosynthesis pathway in chloroplast as in cinmethylin. Inhibition of FAT proteins will decrease lipid formation, induce abnormal and unstable structure of membrane, disturb lipid signaling system related with cell division, and secondarily generate reactive oxygen species. Accordingly, the consequent inhibition of lipid biosynthesis seems to cause an identical symptomology of methiozolin such as rapid cease of meristematic growth, partial chlorosis in newly formed fronds, abnormal growth, and consiquential plant death by a chain reaction (pleiotypic effects).
Figures & Tables
Fig. 1. Chemical structure of methiozolin (A) and cinmethylin (B).