钙对不同成熟期番茄果实的PG活性及其合成的影响

本文研究了钙处理不同成熟期番茄果实对果壁组织中钙含量与转化、多聚半乳糖醛酸酶(PG)活性与 PG 合成的影响。结果表明,钙处理绿熟期的番茄果实可使总钙和可溶性钙含量明显增加,并较多转化为结合钙;后期处理,进入和转化的钙都减少。同样,钙处理愈早,对果实 PG 活性的抑制愈强,绿熟期处理可完全抑制 PG 活性。凝胶电泳结合钌红染色,证明绿熟期果实无 PG,PG 是在果实成熟过程中新合成的。钙处理愈早,对 PG 合成的抑制愈强,绿熟期钙处理可完全抑制 PG 合成。

EFFECT OF THE CALCIUM ON POLYGALACTURONASE(PG)ACTIVITY AND SYNTHESIS AT DIFFERENT RIPENING STAGES OF TOMATO FRUITS

It has been reported that PG is a key enzyme related to the tomato fruit ripening and that the application of calcium can dramatically decrease the PG activity and delay the ripening of fruits.In this paper the effects of calcium treament at various ripening stages on the trans- formation of absorbed calcium,PG activity and PG synthesis in tomato fruits were studied. According to the analysis of calcium by atomic absorption spectroscopy,it was shown that the soluble and total calcium contents in pericarp of fruits treated with calcium at mature-green stage were increased significantly,and that more soluble calcium was transformed into bound calcium.Both the absorption and transformation of calcium decreased in fruits treated with calcium at later stage of ripening.The inhibition of calcium on PG activity was most effec- tive by treatment at mature-green stage,but less effective at later stage of ripening.One reason for the decrease of calcium inhibition was probably due to the decline of calcium absorption as fruit ripening.The polyacrylamide gel electrophoresis of PG showed that PG with a mole- cular weight of 46.7 kD was absent in mature-green fruits,and PG synthesis occurred only at the later stage of ripening.It seems that the earlier the treatment was done the more ef- fective of the calcium inhibition of PG synthesis. Based on the above results,it was concluded that the PG plays a major role in ripening and senescence of tomato fruits,and both PG synthesis and its activity were inhibited by calcium.In order to delay the ripening and senescence of tomato fruits,the treatment with calcium should be done at mature-green stage.