Maleic Hydrazide as a Plant Growth Inhibitor

Abstract

General effects of maleic hydrazide (MH) on 11 spp. (oat, wheat, redtop grass, hybrid maize, pea, peanut, sunflower, Xanthium, tomato, tobacco, and cotton) belonging to 5 distantly related families were detd. Effects on monocots were the same as on dicots. 0.4% maleic hydrazide suppressed meristematic growth in all spp. tested. Maleic hydrazide may readily enter the plant through either the leaves or the roots and be transported rapidly to regions of meristematic activity. The usual sequence of symptoms produced in treated plants is: loss of apical dominance; expansion of leaves already formed, often to a size greater than the controls; production of a darker green color than the controls; increase in production of anthocyanin pigmentation; and some chlorosis. Subsequent behavior depends to a large extent on the amt. of MH given and to some extent on the age of the plant and on the species. At the lowest concns.,generally 0.05%, axillary buds grow at the same rate on treated plants, though the cotyledonary buds develop after the others. At concns. of 0.2-0.4%, vegetative bud development is slow and may not occur. Root as well as top growth is affected by MH. Flowering of the plants tested was remarkably suppressed. Sunflower and peanut treated in the seedling stage rarely produced any flowers. At a concn. of 0.025% MH caused sterilization of the staminate inflorescences in maize when the plants were treated at about the time of microsporogenesis, while the pistillate flowers were fertile. Flowering in Turkish tobacco was prevented either by adding MH to the soil or by spraying the foliage. In photoperiodically induced Xanthium,phyl-lody commonly occurred after treatment.