Safeners as Corn Seedling Protectants against Acetolactate Synthase Inhibitors
Zea mays L., cv. Potro, shoots had a higher level of resistance to imazaquin (IQ) and metsulfuron methyl (M SM ) than roots. Shoot lengths were increased by pretreating the seeds with commercial 1,8 -naphthalic anhydride (N A ) at 1% (w/w) or oxabetrinil at 0.2% (w/w). The growth of shoots of safened seeds was unaffected by 400 nM IQ and by 40 nM MSM. The in vivo activity of acetolactate synthase (ALS) extracted from corn shoots and roots was not affected by treatments with IQ or MSM, but pretreatment of seeds with NA or oxabetrinil, prior to germination, caused an increase in the level of extractable ALS from shoots. ALS activity from roots and shoots of NA-pretreated seedlings was increased to a large degree (> 40% ) when the seedlings were germinated on 40 nM MSM, whereas ALS activities from oxabetrinil-pretreated seedlings were enhanced to a lesser degree (≈20%). ALS from unsafened seedlings was inhibited 21% by 400 nM IQ and 70% by 40 nM MSM in vitro, but ALS from roots of seedlings germinated on 400 nM IQ was not inhibited by 400 nM IQ in vitro.