Studies on the mechanism of retardation of sprouting and occurrence of functional disorders in onion bulbs applied with malefic hydrazide

Abstract

This study was carried out for three years from the viewpoint of structure of maleic hydrazide (MH) to clarify the mechanism of both retardation of sprouting and occurrence of functional disorders in onion bulbs treated with MH.As known that MH has some specific structure of quinone ring, keton groups, conjugatd double bond and hydrazine or hydrazide base and further is an antagonistic substance of uracil, the following chemicals were examined in relation to those phenomena mentioned above, Malefic acid, p-Quinone, Hydrazine dihydrochloride, Phenylhydrazine, Semicarbazide, Isonicotinic acid hydrazide, Thiouracil and MH.1. The results of storage test with bulbs applied with each chemicals respectively before harvest showed that the most effective substance comparable to the inhibiting effect of MH on the sprouting of bulbs is Isonicotinic acid hydrazide, more or less effective ones Hydrazine and Semicarbazide, and less effective ones Maleic acid, p-Quinone, Phenylhydrazine and on the other side more severe substances than MH on the occurrence of decay and functional disorders are Thiouracil, Hydrazine, and Semicarbazide.Consequently it appears that the structure of MH effective for the inhibition of sprouting consist in the form of >C=C-C(=O)-NH-NH- and also that for the occurrence of functional disorders and decay is due to both an analogue of nucleic acid and hydrazine or hydrazide base.2. From the results that both Isonicotinic acid hydra zide and MH antagonized Pyridoxine respectively against the growth of avena coleoptile section it was considered that the inhibiting effect of MH on the sprouting of onion bulbs depends upon the cessation of growth of leaf primordia due to the lowering protein synthesis accompanied by the inhibition of transaminase activity by MH.3. With increase in concentration of each chemical solution the respiration of stem disk slice in onion bulbs was inhibited. Among them Thiouracil gave the most severe effect followed by MH, Isonicotinic acid hydrazide and Hydrazine in the descending order.Consequently it is considered that the occurrence of functional disorders in onion bulbs by MH depends upon respiratory stress due to an analogue of nucleic acid.