Action of Maleic Hydrazide on Dormancy, Cell Division, and Cell Expansion

Abstract

Maleic hydrazide (MH) is of practical and theoretical interest as a growth-regulating chemical that can inhibit plant growth without causing obvious morphological abnormalities (13,14). After recent reports of growth interactions between MH and gibberellic acid (GA) (2, 10), Brian and Hemming called attention to the many growth effects for which MH has actions opposite to those of GA (1). From studies of interactions of MH and GA on pea stem extension, these authors concluded that "MH prevents the response to GA of GA-sensitive plants" and that it is, therefore, likely that "MH inhibits growth by blocking some essential reaction at a stage preceding that where GA normally exerts its effect" (1). In these experiments, we have studied the effects of MH and compared them with those of GA on three systems: lettuce seed germination, mitosis in the absence of growth by expansion in dormant lettuce seeds (5, 7), and growth by cell expansion in the absence of mitosis in y-irradiated wheat (6). The results show that there is no specific interaction between MH and GA either on lettuce seed germination or on the growth of wheat seedlings, and MH seems to exert direct effects on cell division but not on cell expansion during seedling growth [which is in contrast to previously studied GA effects on these same systems (6. 7)]. Similarities between effects of MH and of ionizing radiation are noted. MATERIALS AND METHODSExperiments were performed with lettuce (Lactuca sativa L., var. Big Boston White) and wheat (Triticumz vulgare Vill., (Triticum aestivum L.), var. Thorne). Big Boston White was used because its germination is more sensitive to MH than any of several other varieties we tested. We sowed 100 mg of lettuce seed on one piece of Whatman No. 1 filter paper moistened with 3.5 ml of solution at pH 5.7 in a covered 9 cm Petri dish. The dishes within closed copper sterilization cans (and thus in continuous darkness) were placed in a constant-temperature water bath. The criterion for germination was visual detection of radicle protrusion after 2 days at 260 C. excised, fixed, and examined for mitotic figures as previously described (5, 7). Some wheat grains were given 800 kr of -y rays at 49 kr/hr from a Co60 source described elsewhere (3). The wheat was from the same batch used in previous studies (6) and was grown under the same controlled conditions for 12 days (with light intensity of approximately 450 ft-c during the 16-hour day). Growth was measured as length of the first leaf 12 days after sowing, at which time growth of the irradiated plants growing without mitosis was complete (6). RESULTSIf the suggestion of Brian and Hemming (1), that MH prevents response to GA, is generally true for gibberellin responses then we should expect GA to be less effective than other germination stimulators in relieving the dormancy imposed by MH. Accordingly, we studied the effects of germination stimulators (GA, kinetin, thiourea) in combination with germination inhibitors (MH, coumarin, 2,4-dinitrophenol, mannitol, and nicotine) on...

Kinetic studies of certain anti-gibberellins

“…Thus, the curves are characteristic of responses to two completely independent factors. These results fully confirm the earlier conclusion of Haber and White (6) growth promoting factors in a growth system. To complete the model as it may apply to growth, it is assumed that the catenary sequence above contributes an active product, P, which contributes to growth by catalyzing one step of a primary catenary system.…”

The role of exogenous plant regulators in the dormancy of onion bulbs

“…This conclusion is supported by other findings (Biswas et al 1967;Butenks & Baskakov, 1961;Greulach & Atchinson, 1950;McManus, 1960;Pendergrass, 1969;Zuckel, 1963), which indicated that MH produces its action by inhibiting cell division and that it hinders (blocks) the biosynthesis of ribonucleic acid. Harber & White (1960) indicated that MH acts as antimetabolite of uracil and riboflavin. Other reports (McManus, 1960;Taylorson, 1961;Zuckel, 1963) indicate that MH does not interfere directly in its action with auxins, gibberellins and cytokinins.…”

The Influence of the Plant Growth Regulator Maleic Hydrazide on Egyptian Broomrape Early Developmental Stages and Its Control Efficacy in Tomato under Greenhouse and Field Conditions

“…Only the two highest MH concentrations, 11.2 and 22.4 mM, were able to reduce the seed-germination percentage by 25 and 45%, respectively, as compared to the untreated controls. Lattice seed germination was reduced by 93% in response to 15 mM MH, ( Haber and White, 1960 ), and Grant and Harney (1960) did not find any inhibitory effect on tomato seed germination at 10 mM MH, while Albizia lebbeck L. seeds responded in a positive germination rate to increase of MH concentration ( Tomar, 2008 ). These results demonstrate the variation in seed sensitivity of different plant species to MH.…”

“…These results demonstrate the variation in seed sensitivity of different plant species to MH. Using dormant lettuce and y-irradiated wheat seeds, Haber and White (1960) concluded that MH inhibits cell division but has no effect on cell expansion. Similar experiments were conducted by Hershenhorn et al (1998) with sulfonylurea herbicides.…”