【作者】 李雪梅；

【导师】 彭抒昂；

【作者基本信息】 华中农业大学 ， 果树学， 2008， 硕士

【摘要】 果实中有机酸,是影响果实品质的重要因素之一。前人研究表明,砂梨成熟果实中的有机酸主要为苹果酸和柠檬酸,并且有些品种以苹果酸含量高,有些品种以柠檬酸高,但对出现这种差异的原因并未作出解释。本试验通过对六个典型砂梨品种在生长过程中的苹果酸、柠檬酸含量和有机酸代谢相关酶活性的测定,对代谢相关酶与两种酸的关系进行分析,探讨酶对砂梨有机酸影响以及不同品种有机酸差异的原因。试验结果如下:1.不同砂梨品种苹果酸的动态变化苹果酸含量变化呈现先上升后下降的抛物线变化趋势。品种间的差异主要在于上升和下降的快慢,高苹果酸品种二宫白和梗头青含量在达到最大值后的下降过程都比较缓和,而低酸品种真渝和雁荡雪梨下降相对较快。2.不同砂梨品种柠檬酸的动态变化柠檬酸含量的变化趋势在品种间差异较大,也是先再下降的过程,但上升和下降的速度不同。低柠檬酸含量的湘菊升高和降低都较快。高柠檬酸的雁荡雪梨从第八周开始升高,升速很大,到花后第十八周时升高了13倍,低柠檬酸的梗头青同比仅升高了1.8倍。3.砂梨苹果酸代谢相关酶活性变化NAD-MDH活性变化与苹果酸含量变化基本一致。成熟时,苹果酸含量高的品种,其NAD-MDH活性也高。在砂梨果实的整个生长过程中,与苹果酸含量的相关性很大,相关系数最高可达0.8964^**。NADP-ME在果实生长前期活性较低,几乎是在苹果酸含量开始下降时,NADP-ME活性开始快速升高,果实接近成熟时降低。但果实成熟时,低苹果酸含量品种NADP-ME活性较高。果实生长后期,与苹果酸的相关系数介于-0.9314^*—-0.8284间。PEPC活性与苹果酸含量的变化不太一致,与苹果酸含量没有相关性显著相关性。4.砂梨柠檬酸代谢相关酶活性变化CS活性与柠檬酸含量的变化趋势一致。果实成熟时,柠檬酸含量越高,该品种的CS活性也越高。在整个生长过程中都与柠檬酸含量呈显著相关性,相关系数在0.8284^**以上。PEPC活性与柠檬酸含量变化的一致性相对较大,果实成熟时,柠檬酸含量越高,该品种的PEPC活性也越高,果实生长后期与柠檬酸含量的相关系数在0.7056-0.9484^*间。Cyt-ACO、Mit-ACO活性的变化趋势在各品种中基本相同,但与柠檬酸含量的变化不一致,与柠檬酸含量的相关性不大。NAD-IDH活性变化趋势在各品种中差异较大,与柠檬酸含量相关性也不大。更多还原

【Abstract】 Organic acids are the major facters in fruit affecting the quality of fruit.The studies previously showed that malate acid and citrate acid were the main organic acids in mature sand pear.Some breeds had more malate acid than citrate acid,and others had more citrate acid than malate acid.But no explanation has done to declare the difference.In this study,the contents of malate acid and citrate acid and their relative enzyme activities in six typical breeds of sand pear were assayed,the relationship between the two organic acids and their correlated enzyme activities were analysed to discuss the reason for the difference of composition and content in different sand pears and the impacts which correlated enzyme activities have on organic acids.The results are as followed:1.Dynamic change of malate acid in different sand pearsThe change of malate acid content shows a parabola-like rise-and-fall motif. The significant difference among different varieties lie in different speed when it rises and falls.Er Gongbai and Geng Touqing which have more malate acid fall quite slowly after they arrived their highest value,but Zhen Yu and Yan Dang Snow Pear fall much more quickly.2.Dynamic change of citrate acid in different sand pearsThere are many differences in the change of citrate acid content among different sand pears which also have different speed when it rises and falls.Zhen Yu has low citrate acid content,and the citrate acid content rises and falls slowly.Citrate acid content begins to rise quickly from eight weeks after anthesis,and rises at 13 times to eighteen weeks inYan Dang Snow Pear which has high citrate acid content.At the same stage,Geng Touqing rises at 1.8 times.3.Dynamic change of correlated enzyme activities of malate acidThe change of NAD-MDH activity has the same trend as the change of malate acid.The breed which has more malate acid has higher NAD-MDH activity.It has a big correlation with malate acid content during the development of sand pears.The biggest correlation cofficient 0.8964^**.At early stage of fruit growth,the activity of NADP-ME is low.Hardly when malate acid content start to fall,the activity of NADP-ME begun to rise quickly.It falls just before the mature.The breed which has lower malate acid content has higher NADP-ME activity.At late stage the correlation between them was from -0.9314^* to-0.8284.There is almost no consistence between PEPC activity and malate acid content, and the correlation is not notable.4.Dynamic change of correlated enzyme activities of citrate acidThe change of CS activity has the same trend as the change of citrate acid. When the fruit are mature,the breeds which have more citrate acid have higher CS activity.The correlation coefficient higher than 0.8284^** show a notable correlation between citrate acid and CS activity during fruit deveopments.The change of PEPC activity has simillar trend to the change of citrate acid.When the fruit are mature,the breeds which have more citrate acid have higher PEPC activity.The correlation coefficient is at the late stage is from 0.7056 to 0.9484^*.Cyt-ACO and Mit-ACO activity have no correlation with the change of citrate acid content,but same in different breeds.The change of NAD-IDH activity is different in breeds.There is no significant count between NAD-IDH activity and citrate acid content.更多还原