Syntheses of arylisoxazolylphenylacetic acids and arylisoquinolinones and their plant growth-regulating activities.

Abstract

Sixty-two phenylacetic acid derivatives having phenylpropane skeleton were synthesized. Their physiological effects on the growth of lettuce seedlings were distinguished from those of plant hormones and an antiauxin. The derivatives retarded the growth in a similar manner to the auxin transport inhibitors, NPA and CPD. A few derivatives including 2-[3'-(m-chlorophenyl)isoxazol-5'-yl]phenylacetic acid were up to 10 times as potent as CPD in inhibition of the hypocotyl growth and IAA transport. The phenylacetic acids did not cause, even at high concentrations, any serious damage such as a herbicidal would. Their remarkable growth-retarding effects may be due, at least in part, to their ability to prevent the polar movement of IAA within tissues.