Alachlor and 1,8-Naphthalic Anhydride Effects on Sorghum Seedling Development

Abstract

Time of coleorhiza emergence through the per carp of sorghum [Sorghum bicolor (L.) Moench ‘AKS 614′] germinated on blotters in the dark was not affected by 1, 5, or 25 ppmw of alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide], by 2% w/w 1,8-naphthalic anhydride (hereafter referred to as NA) seed treatment, or their combinations. Coleoptile emergence was delayed slightly by NA alone and in combination with alachlor, but not by alachlor alone. Emergence of the primary leaf from the coleoptile was inhibited by alachlor treatments in the presence of NA and even more so in its absence. Various degrees of leaf distortion resulted when plants not exhibiting leaf emergence were placed in light. Severity of distortion was less with 1 ppmw of alachlor than with 5 ppmw, and the alachlor-induced distortion was less when in combination with 150 ppmw of NA. After 4 weeks the primary leaves were still distorted, but subsequent emerging leaves were normal in all treatments. More complete emergence and unrolling of the primary leaf were observed when terminal segments (3.5 cm long, including the coleoptile and part of the first internode) from plants grown in the presence of 150 ppmw of NA were vacuum infiltrated with 15, 25, and 50 ppmw of alachlor than in the controls. From these results we conclude that the protective action of alachlor is of a physiological nature and not one of physical deactivation of the herbicide.