柑橘果实囊衣发育与化渣性的形成

The Relationship Between Mastication and Development of Segment Membranes in Citrus Fruits

【目的】揭示柑橘果实囊衣发育和化渣性形成的规律,为改良柑橘果实化渣性品质提供理论依据。【方法】以‘爱媛30’杂柑、‘诺瓦’杂柑、‘兴津’温州蜜柑、‘园丰’脐橙、‘纽荷尔’脐橙、‘安江’香柚和‘江永’香柚等不同类型柑橘果实为材料,在细胞及生理生化水平通过比较不同类型柑橘果实囊衣的超微结构、发育过程中囊衣的发育规律,分析囊衣细胞壁主要生理生化指标。【结果】不同类型柑橘果实囊衣均表现出外侧面粗糙而内侧面光滑的特征;囊衣内侧面表面蜡质层明显,其下1-2层细胞排列整齐、细胞壁增厚,囊衣细胞排列致密度由内侧面向外侧面逐渐降低。内侧面蜡质层及其下1-2层细胞形态变化、排列特征的显现是囊衣发育成熟的标志。柚类果实囊衣最厚、化渣性最差,主要原因是其囊衣细胞层数多、细胞体积大、果胶含量高。果实发育过程中,不同柑橘类型果实在花蕾至落花期,其子房内部已分化出心室,未来形成囊衣的心室间隔细胞大小一致且排列紧密,尚无明显的囊衣细胞排列特征。随着果实的膨大及成熟,‘沙田柚’(Citrus grandis Osbeck cv. Shatianyou)果实囊衣发育成熟后细胞壁增厚期最长,厚度最厚且细胞层数多,果胶含量显著高于‘园丰’脐橙(Citrus sinensis Osbeck cv. Yuanfeng)和‘橘湘早’温州蜜柑(Citrus unshiu Marc. cv. Juxiangzao);‘园丰’脐橙囊衣成熟后细胞壁增厚期较长、细胞层数中等,原果胶含量高于‘橘湘早’温州蜜柑;‘橘湘早’温州蜜柑囊衣成熟后细胞壁增厚期最短,厚度最薄、细胞层数最少。10月,温州蜜柑成熟时,‘沙田柚’‘园丰’脐橙和‘橘湘早’温州蜜柑的原果胶含量分别为364.22、208.48和165.39 mg·g-1,‘沙田柚’分别较其他两个品种高74.7%和120.2%。【结论】柑橘果实囊衣厚度、细胞层数和细胞壁增厚程度影响果实化渣性,果胶含量可以反映果实囊衣化渣性程度。

【Objective】 This study aimed to reveal the development of segment membrane, which contributed to citrus fruit mastication, so as to provide the theoretical basis for fruit mastication trait improvement. 【Method】 Using different citrus types(hybrid citruses including Ehime No. 30 and Nova, Okitsu Wase satsuma mandarin, navel oranges including Yuanfeng and Newhall,and pumeloes including Anjiang and Jiangyong) as reseach materials, the main physiological and biochemical properties of segment membrane were analyzed by comparisons in tissue development and cell ultrastructure. 【Result】 The rough outside but smooth inside of segment membrane occurred in all citrus types. Obviously waxy layer grew on the inside of segment membrane under which one or two cell layers with thickened cell wall arranged neatly. Cell density decreased gradually from inside to outside in segment membrane. Occurrence of wax layer in the inside and morphological changes of cells under the wax layer emblematized the maturation of citrus segment membrane. For pomelo, the thickest segment membrane linked with the worst mastication was caused from a large number of cell layers, enlarged cell size and more pectin in segment membrane. At early fruit development from squaring stage to flower withering stage, the ventricles differentiated already in the ovary, and the intervals between ventricles would develop into segment membranes. In the period, parenchyma cells in the intervals exhibited equal cell size and arranged neatly,having no segment membrane characteristics. With fruit enlargement and maturation, the segment membranes of Shatian pomelo had the most cell layers and the longest cell wall thickening period. Segment membranes of Shatian pomelo showed significantly higher pectin content than that of Yuanfeng navel orange and Juxiangzao Satsuma mandarin. Segment membranes of Yuanfeng navel orange had medium cell layers and moderate cell wall thickening period, in which protopectin was higher than that of Juxiangzao Satsuma mandarin. The segment membranes of Juxiangzao exposed the least cell layers and the shortest cell wall thickening period. In October when Juxiangzao matured, segment membrane protopectins in Shatian pomelo, Yuanfeng navel orange and Juxiangzao Satsuma mandarin were 364.22, 208.48 and 165.39 mg·g-1, respectively, with Shatian pomelo reaching 74.7% and 120.2% higher than another two varieties. 【Conclusion】 Segment membrane thickness, cell layers in segment membrane and degree of cell wall thickening associated with citrus fruit mastication. Pectin content could reflect the mastication of citrus segment membranes.