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Maleic Hydrazide as a Plant Growth Inhibitor

Botanical Gazette1950Vol. 112(1), pp. 112–126

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Abstract

1. General effects of maleic hydrazide upon eleven species belonging to five distantly related families of plants have been determined. 2. Data thus far assembled indicate that maleic hydrazide has remarkably similar effects on monocotyledonous and dicotyledonous plants. This generalization holds in terms of morphological response of plants of a given physiological age group to a given concentration of the substance. 3. Seedlings are most sensitive to maleic hydrazide; but it can inhibit growth at any stage up to maturity without killing the plant. Generally, in the plants tested, a spray of 0.4% concentration will cause all meristematic growth to cease. 4. Evidence was obtained which indicates that maleic hydrazide may readily enter the plant through either the leaves or the roots and be rapidly transported to regions of meristematic activity. 5. The usual sequence of symptoms produced in treated plants is: (a) loss of apical dominance; (b) expansion of leaves already formed, often to a size greater than the controls; (c) production of a noticeably darker green color than the controls; (d) increase in production of anthocyanin pigmentation; and (e) some chlorosis. Subsequent behavior depends to a large extent upon the amount of maleic hydrazide given and to some extent upon the age of the plant and upon the species. 6. At the lowest concentrations, generally 0.05%, axillary buds of seedlings begin to grow very soon after treatment. Virtually all axillary buds grow at the same rate on treated plants though the cotyledonary buds develop a little after the others. Usually the leaves on the new branches are malformed and may be quite "stringy"; often the veins grow more slowly than the interveinal tissue. This results in a rather rough texture. In some of the plants which were allowed to grow a very long time after treatment, normal-appearing leaves were finally produced. 7. At the higher concentrations of maleic hydrazide (0.2-0.4%) vegetative bud development is slow to occur and may not occur at all. 8. Root as well as top growth is affected by maleic hydrazide, but under the conditions of these experiments roots were less affected than the tops. Wheat root growth was not affected by the concentrations used; root growth in oats was suppressed almost as much as that of the tops; but maize roots were suppressed more than the tops. 9. Flowering in the plants tested was remarkably suppressed by maleic hydrazide. Sunflower and peanut treated in the seedling stage rarely produced any flowers. At a concentration of 0.025% maleic hydrazide caused sterilization of the staminate inflorescences in maize when the plants were treated at about the time of microsporogenesis; but fertile pistillate flowers were produced under similar conditions. Flowering in Turkish tobacco was prevented either by adding maleic hydrazide to the soil or by spraying the foliage. In photoperiodically induced Xanthium phyllody commonly occurred after treatment. 10. The argument that maleic hydrazide may have considerable theoretical as well as practical value as a growth inhibitor is developed.

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Abstract

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