| Summary: | 碩士 === 國立臺灣大學 === 農藝學研究所 === 65 === The purpose of this study was to find out the effects of plant hormones on the activity of aryl acylamidase during rice germination and seedling growth. Rice seeds, leaf segments and seedlings were treated or incubated with GA3, ABA, IAA, 2,4-D, and Kinetin respectively for several days or weeks at controlled temperature. They were then assayed for the aryl acylamidase activity. The results were summarized as follows:
1.Incubation of the hormones in the assay mixtures with partially purified aryl acylamdiase indicated that hormones did not affect enzyme activity in vitro.
2.A decrease in the activity of aryl acylamidase In both incubated half seeds and germinating intact seeds was observed. The decrease was more rapidly in embryoless half seeds than embryo half seeds or intact seeds during incubation.
3.GA3 treatment could effectively promote the decreasing rate of enzyme activity in embryoless half seeds. The effect was increased with increasing concentration and reached a maximum at 10(-5)M. ABA alone was no effect, but it could overcome the effect of GA3. IAA, 2,4-D and kinetin had no significant effects on enzyme activity.
4.The effects of hormone treatment on intact seeds was the same as in embryoless half seed except of IAA which could slightly increase enzyme activity, but the effects were smaller than the embryoless half seeds.
5.CaSO4 could increase the decreasing rate of enzyme activity in embryoless half seeds especially when treated with GA3.
6.When cycloheximide was added into the incubation medium, the activity of aryl acylamidase in the seeds and leaf segments could be conserved. The antibiotic also completely eliminated the effects of hormone treatment.
7.A process sensitive to inhibit the decrease of enzyme activity by cyclohexmide occurred between 0 and 2 days after incubation when the embryoless half seeds were incubated in water, but the time of sensitivity to cycloheximide always existed when the seeds were incubated in GA3.
8.Leaf segments incubated with hormones for 3 days showed that GA3 still increased the decreasing rate of enzyme activity; kinetin and IAA slightly Increased the enzyme activity; ABA and 2,4-D were no effects.
9.Treatment of hormones in the nutrient solution showed that GA3 and IAA could not influence enzyme activity; after 2 weeks of treatment, kinetin could largely increase enzyme activity; after 1 week of treatments, 2,4-D could slightly increase enzyme activity, but was disappeared after 2 weeks of treatment.
10.Results of the present study suggested that de novo synthesis of aryl acylamidase appeared to be not occurred in rice embryoless half seeds during incubation. The enzyme probably was synthesized before seed maturation and gradually degraded by proteolytic enzymes during germination.
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