采前钙处理对水蜜桃(Prunnus persica L.)果实软化过程中蛋白质代谢的影响

采前喷钙处理,采收后12天的贮藏过程中,水蜜桃果实的果皮和果肉的钙含量均提高,呼吸高峰推迟出现,呼吸强度明显降低;且果肉中总蛋白质和可溶性蛋白质的SDS—PAGE组分亦发生变化;采后的前6天,钙处理的果实中未出现对照组果实中所出现的某些蛋白质组分(约113.9KD,43.66KD.53.1KD,58.3KD,和66.2KD),同时,经钙处理后,果实蛋白质水解酶活性提高,游离态氨基酸含量则比对照低,且稍上升后即保持稳定.进一步的超离心技术分离测定表明,钙处理的果实中,无论是游离态还是膜结合态的核糖体,其含量高峰的出现均晚于对照组,且峰值下降约3.5倍.

Effect of preharvest calcium treatment on the metabolism of protein in peach fruits (Prunnua persica L. )during softening.

Preharvest calcium treatment caused changes on the concentration of calcium,the respiration rate and the metabolism of proteins in peach fruits during subsequent storage for 12 days. The amount of calcium within peel and flesh was increased, which greatly reduced the level of respiration and delayed its peak for four days. While the soluble proteins of untreated fruits increased gradually during softening, that of the calcium treated fruits maintained at a lower level. SDS-PAGE profiles of soluble proteins were also different. Five polype-tides with molecular weights of approximatly 13. 9KD,43. 6KD,53.1KD and 66. 2KD appearing in untreated fruits were not seen in calcium treated fruits,until the sixth day after harvest-In addition,proteinase activity in calcium treated fruits was greater than in untreated ones, while free amino acids concentrtion was still lower from the sixth to the twelveth day of storage. Furthermore,the total ribosome, including the free and membrane -bound ribosome contents in the treated fruits,reach its peak four days latter than that of the untreated fruits did, with much lower quantity. These results suggested that preharvest calcium treatment could alter significantly the protein status in peach, by controling the synthesis of senecence - related proteins, or by promoting the prote-olytic activity to protect the cellular structure.