Malformins, a small family of cyclic pentapeptides, are active plant growth regulators isolated from the fungus Aspergillus niger. We purified malformin A1 from the crude malformin A mixture, and studied its action in the gravitropic response of maize roots. Intact primary roots that had been pretreated vertically with malformin A1 were placed in a humidified box in the horizontal position. Positive curvature (downward) was inhibited in the pretreated roots compared with the control. In addition, we measured the lateral transport of IAA in primary roots. Roots pretreated with malformin A1 did not show asymmetric distribution of IAA between the upper and lower sides of the elongation zone. Malformin A~ also stimulated ethylene production in maize root segments. Our results had suggested that maiformin A1 might inhibit the lateral transport of IAA across the roots from the upper to the lower side because of an increased level of ethylene. Therefore, we placed more IAA on the upper side at the initial phase of gravistimulation. These results were consistent with malformin Al-pretreated roots showing inhibited positive gravitropic curvature.

Ethylene production was measured in mungbean hypocotyls in the presence of far infrared rays emitted from ceramic powder using a gas chromatography. Both IAA-and 1-aminocyclopropane-l-carboxylic acid (ACC)-induced ethylene production was inhibited by 20-30% of the control by indirect application of the ceramic powder. These data suggested that far infrared rays emitted from ceramic powder might act on the conversion step of ACC to ethylene. Furthermore, the activity of ACC oxidase, acting on the conversion of ACC to ethylene, was also inhibited by 20% of the control by indirect treatment of the ceramic powder. These results suggested the possibility that inhibition of ethylene production by far infrared rays emitted from ceramic powder could be used for increasing the period of storage and freshness of crops, fruits, and vegetables.