紫茉莉花衰败过程中的生理、生化及细胞学变化

PHYSIOLOGICAL, BIOCHEMICAL AND CYTOLOGICAL CHANGES IN SENESCING COROLLA OF FOUR O′CLOCK FLOWER

紫茉莉花（Ｍｉｒａｂｉｌｉｓ ｊａｌａｐａ Ｌ．）衰败过程中发生着大分子物质的降解，水解酶活性的增强及乙烯合成的迅速增加。ＲＮＡ、蛋白质含量迅速减少，游离核苷酸及氨基酸含量增加，ＲＮａｓｅ活性明显增强，ＤＮＡ 含量及ＤＮａｓｅ 活性无明显变化。乙烯合成在花衰败前有明显增强现象。放线菌酮有抑制ＲＮａｓｅ活性增强及乙烯合成的能力，在适当的浓度下有延长紫茉莉花开花时间的作用。花衰败过程伴随着细胞结构的解体。

Senescing corolla of Four O′clock flower (Mirabilis jalapa L.) was accompanied by a decline in the contents of RNA and protein as well as an increase of free nucleotides and amino acid but with no change in DNA content. SDS PAGE of proteins showed a gradual reduction in the molecular weight of protein. RNase activity increased obviously but there was no change of DNase activity. Prior to flower wilting the peroxidase activity increased and the rate of ethylene production reached it′s the highest level. When isolated corolla lobes were floated on distilled water, RNase activity and ethylene production increased dramatically in a few hours. But if they were floated on cycloheximide solution, the increase of RNase activity and ethylene production were completely inhibited. Cycloheximide (0 5—1 0 ppm) could extend the longevity of Four O′clock flower outtings. Electron micrographs showed that starch grain disappeared after flowering. However, no significant disintegration is observed in cell nucleus and mitochondria during senescence of corolla.