Abscisic acid (ABA) reduced growth in a root test (lentil), but the inhibition observed was less noticeable than that produced by using indol-3yl-acetic acid (IAA) alone. When both ABA and IAA were employed together, ABA acted as a growth-antagonist of IAA. ABA produced a strong inhibition of the total RNA accumulation and accelerated the RNase activity, while IAA strongly stimulated the RNA accumulation and greatly inhibited RNase activity. When ABA and IAA were tested together, ABA also acted as an antagonist of TAA.