Herbicide Hordeum

Murty KV, Raju DSS, Sharma CBSR. 1983. Cytogenetic hazards from agricultural chemicals 7. Herbicides, fungicides and insecticides screened for effects on chiasmata in Hordeum vulgare. Biologisches Zentralblatt (Leipzig) 102 571-576. 

Aryloxyphenoxypropanoates and cyclohexanediones are herbicidal to most monocotyledons but not to dicotyledons. A comparison between a susceptible species, barley (Hordeum vulgare), and a tolerant species, soybean (Glycine max) showed that haloxyfop was effective in reducing lipid biosynthesis in barley but not in soybean leaf discs (Table I). 

CDAA (N-N-diallyl-2-chloroacetamide) was reported to reduce mitosis in barley (Hordeum vulgare L.) roots nearly 90% after 96 h at 57 yM (38). Propachlor (2-chloro-N-isopropylacetanilide) totally inhibited mitosis in onion (Allium cepa L.) root tips after an 18 h treatment with 75 yM (3 ). At 20 yM cell division was reduced approximately 50% and cell enlargement was reduced 40% in oat coleoptiles (39). After 24 h, 100 yM ioxynil (4-hydroxy-3,5-diiodobenzonitrile) reduced the mitotic index in broad bean (Vicia faba L. ) and pea root tips ( ). Few herbicides that inhibit cell division have been studied in adequate detail to locate the site of the block. A notable exception is the herbicide chlorsulfuron (DPX 4189, 2-chloro-N- [(4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl -benzenesulfonamide) ( ). Ray reported a 50% reduction in corn growth 3 h after treatment with 28 yM chlorsulfuron. Mitosis in broad bean root tips was significantly reduced by 2.8 yM, whereas in three different tests, cell enlargement was not influenced with concentrations of 28 yM. Thymidine incorporation into DNA was inhibited in corn root tips after a 1 h treatment with... 

Intensive use of the herbicide paraquat has resulted in the evolution of resistance in various weed species. Intensive research on the resistance mechanisms was mainly carried out with resistant biotypes from Hordeum spp. and Conyza spp., and altered distribution of the herbicide in the resistant weeds was suggested as the cause - or at least the partial cause - of resistance. In resistant Conyza canadensis it was supposed that a paraquat inducible protein may function by carrying paraquat to a metabolically inactive compartment, either the cell wall or the vacuole. This sequestration process would prevent the herbicide from getting in sufficient amounts into the chloroplasts as the cellular site of paraquat action. Inhibitors of membrane transport systems, e.g., N,N-dicyclohexylcarbodii-mide (DCCD), caused a delay in the recovery of photosynthetic functions of the paraquat-resistant biotype, when given after the herbicide. These transport inhibitor experiments supported the involvement of a membrane transporter in paraquat resistance [75]. 

Translocation studies with two paraquat-resistant biotypes of Hordeum lepori-num revealed that the basipetal transport of paraquat in resistant H. leporinum was much reduced compared with susceptible plants. It was concluded that the resistance to paraquat was the result of the reduced herbicide translocation out of the treated leaves [76]. One can suppose that also in this species herbicide sequestration may have been the primary cause for the altered long-distance transport. 

Lichtenthaler H.K. and Kleudgen H.K., 1977. Effect of the herbicide San 6706 on biosynthesis of photosynthetic pigments and prenylquinones in Raphanus and in Hordeum seedlings. Z. Naturforsch. 32c, 236-240. 

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