Brassinolide is a plant-growth regulator.In this study,the toxicity and cocooning effects of 14-hydroxybrassinosteroid,24-epibrassinolide and 28-epihomobrassinolide on silkworm were studied.The result showed that the 14-hydroxybrassinosteroid and 24-epibrassinolide solution di-luted 1 000～16 000 times did not produce toxicity to the 2nd to 5th instar silkworm.The 2nd instar silkworm showed poisoning symptoms 48 h after feeding with 28-epibrassinolide diluted 16 000 times.24 h after feeding 28-epihomobrassinolide solution diluted 4 000-fold,the 2nd and 3rd instar silkworms exhibited poisoning symptoms,and the 4th instar silkworms showed poisoning symptoms at 48 h.After feeding with 28-epihomobrassinolide diluted by 1 000,2 000 and 3 000 times at 24 h,the 5th instar silkworm displayed poisoning symptoms.However,the symptoms of poisoning gradu-ally eased and disappeared when silkworms were fed normal mulberry leaves.Only 28-epibrassinol-ide had a certain effect on the cocooning of silkworm when the three kinds of brassinolide solutions were diluted 4 000～16 000 times.It is therefore recommended to use 14-hydroxy brassinosteroid and 24-epibrassinolide in the diseases control and protection of crops.
维普
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