Influence of ripening and turgor on the tensile properties of pears: A microscopic study of cellular and tissue changes
Influence of ripening and turgor on the tensile properties of pears: A microscopic study of cellular and tissue changes
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DOI：
10.21273/jashs.125.3.350
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发表时间：
2000-05-01
影响因子：
1.9
通讯作者：
De Baerdemaeker, J
中科院分区：
文献类型：
--
作者：
De Belie, N;Hallett, IC;De Baerdemaeker, J
采用显微镜装置对欧洲梨（Pyrus communis L，'Beurre Bose'）和亚洲梨（Pyrus pyrifolia Nakai 'Choguro'）的拉伸性能进行了研究，该装置允许在测试期间直接观察和记录细胞和组织的变化。为了操纵膨压势，将来自不同硬度（成熟度）的果实的组织切片在不同材料势的蔗糖溶液中孵育。针对单个果实调节溶液水势，并且从压榨的汁液的水势在-2.5和IMPa之间变化。果实硬度下降，从100至20 N和60至25 N的欧洲和亚洲梨成熟过程中。欧洲和亚洲梨果实硬度与组织在等渗溶液中的抗拉强度之间的关系呈S形，组织破坏的主要机制是细胞壁的破坏和细胞破裂在高硬度和细胞间的脱粘在低硬度。在果实硬度和组织抗拉强度同时下降的中间区，可以观察到细胞壁破裂和细胞间脱粘的混合物。组织和细胞在最大力下的延伸都随着果实软化而下降。来自硬梨的组织的拉伸强度（>50 N硬度，>0.8 N拉伸强度）在比细胞汁液更浓缩的溶液（高渗溶液）中孵育期间降低多达0.6 N。当类似的组织切片在浓度低于细胞液的溶液中孵育时，（低渗溶液）时，抗张强度增加高达0.4N，这被解释为细胞壁响应于细胞膨压增加的应力硬化。来自软梨的组织的抗张强度不受渗透变化的影响，因为组织破坏的机制是细胞与细胞的脱粘而不是细胞壁破坏。
The tensile properties of european pear (Pyrus communis L, 'Beurre Bose') and asian pear (Pyrus pyrifolia Nakai 'Choguro') were examined using a microscope-mounted apparatus that allowed direct observation and recording of cell and tissue changes during testing. To manipulate turgor potential, tissue slices from fruit of different firmness (ripeness) were incubated in sucrose solutions of differing mater potential. Solution water potentials were adjusted for individual fruit, and varied between -2.5 and 1 MPa from the water potential of the expressed juice. Fruit firmness declined from 100 to 20 N and from 60 to 25 N during ripening of european and asian pears, respectively. For both european and asian pears the relationship between fruit firmness and tensile strength of tissue soaked in isotonic solutions was sigmoidal, with the major mechanism of tissue failure being cell wall failure and cell fracture at high firmness and intercellular debonding at low firmness. In the intermediate zone, where fruit firmness and tissue tensile strength decreased simultaneously, a mixture of cell wall rupture and intercellular debonding could be observed. Tissue and cell extension at maximum force both declined similarly as fruit softened. Tensile strength of tissue from firm pears (>50 N firmness, >0.8 N tensile strength) decreased by as much as 0.6 N during incubation in solutions that were more concentrated than the cell sap (hypertonic solutions). When similar tissue slices were incubated in solutions that were less concentrated than the cell sap (hypotonic solutions), the tensile strength increased by up to 0.4 N, This is interpreted as stress-hardening of the cell wall in response to an increase in cell turgor, Tensile strength of tissue from soft pears was not affected by osmotic changes, as the mechanism of tissue failure is cell-to-cell debonding rather than cell wall failure.