Herbicidal activity against monocotyledonous plants

However, the herbicidal activity against monocotyledonous plants such as barnyard grass and crab grass decreased with the growth of seedlings. 

All tested compounds, such as IC-22, IG-21, and HD-10 showed much higher inhibitory potency against PDHc from dicotyledons (pea or mung bean) than their inhibitory potency against PDHc from monocotyledon (rice). They also exhibited higher herbicidal activity against dicotyledonous plants (such as pea, common amaranth, rape) than monocotyledonous plants (such as barnyard grass and rice). The data are listed in Table 7.6. 

The herbicidal activities of hydantocidin and comexistin against annual monocotyledonous plants are shown in Table 2. The results are also compared with those of glyphosate and bialaphos. Hydantocidin and comexistin had potent herbicidal activity against most of the monocotyledonous plants, almost or great as glyphosate, and stronger than bialaphos. 

As described in Chaps. 2-6, most of l-(substimted phenoxyacetoxy)alkyl-phosphonates with 2,4-Cl2 as on the phenoxy-benzene ring exhibited much better herbicidal activity against dicotyledons than monocotyledons. Therefore, some alkylphosphonates and the corresponding sodium salts with 2,4-Cl2 as were chosen to examine their inhibition against PDHc from both dicotyledons and monocotyledons plants in vitro. Mung bean (V. radiata) and pea (Pisum sativum) as representative dicotyledonous plants, rice Oryza sativa) as a representative monocotyledonous plant were used in enzyme assays. The IC50 values of the tested compounds against plant PDHc are listed in Table 7.3. 

The above observations showed that HWS had good herbicidal activity against dicotyledonous weeds, but relatively weak effects against monocotyledonous plants, indicating that HWS should be considered as an selective herbicide against dicotyledonous weeds. 

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