Alachlor and Gibberellic Acid Interaction on Corn Tissues

The effect of alachlor [2-chloro-2′,6′-diethyl- N -(methoxymethyl)acetanilide] and gibberellic acid (GA 3 ) on increase in length of corn ( Zea mays L.) epicotyl segments and the interactions between alachlor (0, 5 × 10 -6 , 5 × 10 -4 , 4.4 × 10 -4 , and 5 × 10 M) and GA 3 (0, 1 × 10 -6 , 2.8 × 10 -4 , and 1 × 10 -4 M) were investigated. Alachlor significantly inhibited growth of these segments while GA 3 usually increased growth. GA 3 in combination with alachlor caused a significant increase in growth compared to alachlor alone resulting in growth comparable to that occurring in untreated tissues. The magnitude of GA 3 induced growth in the presence of alachlor depended upon the concentrations of the herbicide and GA 3 employed. Alachlor was, however, able to inhibit the GA 3 induced growth. The maximum degree of growth inhibition resulted from exposure of the segments to alachlor with or without GA 3 from the start of incubation. This inhibition decreased as the exposure to alachlor was delayed. Alachlor started inhibiting growth in the presence of GA 3 after the first 9 hr of incubation and after the first 21 hr of incubation in the absence of GA 3 .