P-CPA increases the endogenous IAA content of parthenocarpic muskmelon fruit

Abstract

We examined the effects of seed formation andpara-chlorophenoxyacetic acid (p-CPA)treatment on the growth and endogenous indole acetic acid (IAA) content ofmuskmelon fruit. The growth of parthenocarpic muskmelon fruit induced by 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) declined 15 days after anthesis (DAA),resulting in smaller fruit than those pollinated at harvest.p-CPA improved the growth of parthenocarpic fruit thatweretreated between 10 and 25 DAA. Endogenous IAA levels in the seedsof artificially pollinated fruit were at their highest at 10 DAA,then decreased, and increased again after 30 to 45 DAA, whereas,the levels in the empty seeds of parthenocarpic fruit were significantly lowerthroughout development. Although endogenous IAA levels in the placenta ofpollinated fruit were lower than those in the seeds, the changing patterns werevery similar to those in the seeds. Endogenous IAA levels in the mesocarp ofpollinated fruit remained lower than those in the placenta throughout fruitgrowth, and the pattern of change was similar to that of the placenta. Levelsinthe seed, placenta and mesocarp of p-CPA-nontreatedparthenocarpic fruit stayed lower than those in pollinated fruit.p-CPA increased the levels of IAA in the seeds, placenta,and mesocarp of parthenocarpic fruit after the first treatment (10DAA) to 15 DAA, while those in the mesocarp increasedsignificantly after the second treatment (25 DAA), but did notincrease in empty seed and placenta.