Morphogenetic effect of phenylboric acid on various leaf-shape mutants in the tomato, duplicating the effect of thelanceolate gene

Summary Treatment of germinating tomato seeds ofnormal (La ⁺/La ⁺),lanceolate (La ⁺/La) and several other leaf-shape mutants with phenylboric acid (PBA) duplicates the action of theLa gene with respect to the following: 1) Causes an increase in the level of activity of the four oxidative enzymes tyrosinase, laccase, peroxidase and catalase; 2) causes a corresponding change in leaf form; 3) shows a concentration effect similar to the dosage effect exhibited by theLa gene with respect to both the increase in the activity of oxidative enzymes and a change in leaf form; 4) causes changes, when applied to plants carrying any of several leaf-shape mutants, similar to those caused by theLa gene when the latter is in combination with these leaf shape mutant genes. Based on previous evidence and the current evidence, it is suggested that the primary action of PBA as well as of theLa gene, is to cause the increase in the level of activity of the four oxidative enzymes and the latter in turn, among other factors, determine the shape and size of the leaf in the tomato.