Analysis of apoplast pH as a factor for regulating fruit development and maturation of persimmon.

在柿子生长第三期，果实外质体酸性转化酶将进口蔗糖降解为己糖（葡萄糖和果糖）是影响果实发育成熟的重要因素。果实外质体酸性转化酶的活性受多种因素的调控，尤其是外质体的pH和糖浓度。在本项目中，我们试图明确果实中外质体的糖组成和pH，并表征外质体中酸转化酶作为调节果实发育和成熟的因素的特性。第一次获得的40多毫升样品似乎被韧皮部液污染，通过压力脱水技术可以得到外质体液。外质体的糖主要由己糖（葡萄糖和果糖）占据，而不是蔗糖，尽管果实的糖积累类型。蔗糖积累型和己糖积累型品种的胞体中均含有己糖。在第三生长阶段，去花萼显著抑制了果实的发育和成熟。与这种抑制作用一致的是，果实中己糖浓度和外质体酸性转化酶活性均未增加。这些结果表明，外质体糖代谢在果实发育和成熟过程中起着重要作用。外质体的pH约为6.5，不是酸转化酶活性的最适pH。转化酶活性的最适pH值在4.5左右。虽然这一结果似乎表明，外质体的pH值并不是外质体转化酶活性的调节因子，但也有可能外质体的pH值并不均匀。我们应该更详细地调查这一点。

The degradation of imported sucrose to hexoses(glucose and fructose)by acid invertase at apoplast of the fruit is an important factor for development and maturation of the fruit during growth stage III of persimmon. The activity of acid invertase at apoplast of the fruit seems to be regulated by several factors, especially pH and sugar concentration in the apoplast. We attempted in this project to make clear the sugar composition and pH of apoplast in the fruit and to characterise the properties of acid invertase at the apoplast as a factor for regulating fruit development and maturation.1. The apoplast fluid could obtain by pressure dehydration techniques by removing the first obtained 40mul sample, which seemed to be contaminated by phloem fluid.2. Sugar of apoplast was occupied mainly by hexoses(glucose and fructose), not by sucrose, despite sugar-accumulating types of the fruit. Both sucrose-and hexose-accumulating cultivars showed to have only hexoses in their apoplast.3. Calyx lobe removal of the fruit remarkably inhibited development and maturation of the fruit during growth stage III.Coincident with this inhibition, the fruit did not show the increase of hexose concentration and activities of acid invertase in apoplast. These results showed an important role of sugar metabolism in apoplast on fruit development and maturation.4. The pH of apoplast showed around 6.5 which was not the optimum pH for acid invertase activity. The optimum pH of invertase activity were around 4.5. Although this result seems to indicate that pH of apoplast is not a regulating factor of invertase activity at apoplast, there is a possibility that the pH is not uniform in apoplast. We should investigate this point in more detail.