Maleic hydrazide-auxin interractions in water uptake of potato discs

Taylorson, R. B.; Holm, L. G.

doi:10.1104/pp.36.4.465

Cited by 7 publications

(3 citation statements)

References 18 publications

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“…Only 9% of the radioactivity is in the "nuclear fraction," which is no doubt impure and probably includes the smaller cell wall fragments. Taylorson and Holm (19) have also reported that the '4C-MH is bound to some unspecified but readily centrifuged material in potato disks. Thus it appears likely that most of the 14C is bound in the cell walls; however, definitive proof will have to come from radioautographs.…”

Section: Resultsmentioning

confidence: 99%

“…Thus far, the data provide scant support for the existence of a low molecular weight intermediate in the binding of MH, but they do show that MH is relatively stable, at least in the tissues used here. Other workers (8,17,19,20,23) have also found MH to be stable in higher plants with the exception that a glycoside may be formed, possibly a detoxification product. In contrast, Biswas, Hall, and Mayberry (3) report that tea plants growing in a mineral nutrient solution with '4C-MH degrade the MH.…”

Section: Resultsmentioning

confidence: 99%

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Metabolism and Binding of ¹⁴C-Maleic Hydrazide

Noodén

1970

Plant Physiol.

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Maleic hydrazide (MH) is taken up by corn and pea seedling roots and bound to some material which is insoluble in 80% ethanol or 5% trichloroacetic acid. 14C-MH is stable metabolically; chromatography of the 80% ethanol-soluble 'IC from treated corn roots and tobacco pith gives no indication of degradation. Very little 14C-MH is bound in the zone of cell division (where MH acts to inhibit root elongation) or even in the region of cell enlargement in corn roots and most is bound 1 or more centimeters behind the tip. Likewise, very little MH is bound in corn coleoptile and tobacco pith sections. About 90% of 14C-MH bound in corn roots is associated with large particles which may be cell wall fragments. The binding is blocked by azide and dinitrophenol, indicating a requirement for metabolic energy; however, inhibitors of protein synthesis (chloramphenicol, puromycin, cycloheximide) and DNA synthesis (fluorodeoxyuridine) do not inhibit binding. Only very small amounts of MH are bound in root homogenates, providing further evidence that the binding process is active. Once the MH is bound in the roots, the complex is stable for at least 1 week. Treatment with 2-aminoethanol releases MH.Over the past 2 decades, maleic hydrazide has attracted a great deal of research effort by plant physiologists and cytologists because of its effects on development and chromosome structure; however, its mechanism of action is still unknown (8,16,24). Several years ago Callaghan and Grun (4) and Baker (2) reported that 14C-MH2 was bound selectively in the nuclei of root tips. Thus it appeared likely that a study on the binding of MH would shed some light on how it acts. This paper is concerned with the uptake of MH, its metabolic stability, and some of the characteristics of its binding to some unidentified macromolecule(s). A preliminary report of these findings has been made (14). MATERIALS AND METHODSSeeds of Zea mays Michigan 250 RF hybrid (a yellow field corn) were surface sterilized and germinated in vermiculite as described elsewhere (15). The corn coleoptile sections, tobacco pith explants, and pea seedlings (Pisum sativum variety Alaska)were also grown and prepared as before (15,16 14C-Maleic hydrazide with the label in the 1-position and a specific radioactivity of 4.12 mc/mmole was obtained from Tracerlab, Waltham, Mass. The radiochemical purity of all batches of '4C-MH was checked by descending chromatography using three solvent systems. These were n-butanol, concentrated acetic acid, H20 (6:1:2, v/v); i-propanol, concentrated ammonia, H20 (60:15:25, v/v); and 72% crystalline reagent phenol, 28% H20 (w/v). More than 99% of the 14C-MH was in the MH peak; no other peaks of radioactivity could be detected. In the three solvents used above the RFS of "4C-MH were 0.7 to 0.8.To determine the rates of uptake and binding of 'IC in corn roots, the seedlings were incubated with their roots in aerated 14C-MH solution containing chloramphenicol to suppress bacterial growth (15,18,22). After thorough washing and excision, the ro...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Metabolism and Binding of ¹⁴C-Maleic Hydrazide

Noodén

1970

Plant Physiol.

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“…II. 15,26,28,30,31). Altbougb MH'does iu)t seem to" inbibit cell enlargement in most cases, it was considered necessary to re-examhie this problem in connection witb experiments on its mode of ac'tion.…”

Section: Resultsmentioning

confidence: 99%

The Mode of Action of Maleic Hydrazide: Inhibition of Growth

Noodén

1969

Physiologia Plantarum

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Maleic hydrazide (MH) inhibits corn root elongation through an effect on cell division apparently without inhibiting cell enlargement. The decrease in the rate of elongation was apparent only after a considerable lag, over 14 hours, even with a concentration as high as 5 mM. MH (1 mM) did not inhibit His growth of roots from corn seeds given very large doses of γ‐irradiation or excised corn root segments including the elongation Zone or the cell enlargement induced by IAA in corn coleoptile sections. Many compounds including purines, pyrimidines, nucleosides. cysteine, pyridoxal, pyruvate. kinetin and CoCl2, many of which had previously been reported to alleviate MH inhibition in other tissues, were tested for their ability to prevent the inhibition of corn root elongation by MH, but none were effective. These data do not support the theory that MH acts by inhibiting the synthesis of or competing with some simple metabolite or hormone. Whatever its mechanism of action the failure of MH to inhibit cell enlargement in most systems indicates that it is fairly selective.

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