Thomas Tyler R, Matthews Mark A, Shackel Ken A
Department of Viticulture and Enology, University of California, Davis, CA 95616-8683, USA.
Plant Cell Environ. 2006 May;29(5):993-1001. doi: 10.1111/j.1365-3040.2006.01496.x.
Vitis vinifera L. berries are non-climacteric fruits that exhibit a double-sigmoid growth pattern, and at the point known as 'veraison', which is just before the beginning of the second period of rapid fruit growth, these berries undergo several abrupt physiological changes. Cell pressure probe was used to examine the in situ turgor (P) of cells in the mesocarp during berry development and in response to plant water deficits. Initial tests comparing attached and detached berries demonstrated that cell P was stable for up to 48 h after detachment from the vine, provided that water loss from the berry was prevented. Cell P at pre-dawn was on the order of 0.25 MPa pre-veraison (PreV) and was reduced by an order of magnitude to 0.02 MPa post veraison (PostV). Cell P declined slightly but significantly with depth from the berry surface PreV, but not PostV. When water was withheld from potted vines, cell P declined about 0.2 Mpa, as pre-dawn vine water potential declined about 0.6 MPa over 12 d, whereas cell P was completely insensitive to a 1.10 MPa decrease in pre-dawn vine water potential after veraison. Rewatering of stressed plants also resulted in a 24 h recovery of cell P before, but not after veraison. The substantial decline in cell P around veraison is consistent with the decline in berry firmness that is known to occur at this time, and the PostV insensitivity of P to changes in vine water status is consistent with current hypotheses that the PostV berry is hydraulically isolated from the vine. The fact that a measurable P of about 0.02 MPa and typical cell hydraulic/osmotic behaviour were exhibited in PostV berries, however, indicates that cell membranes remain intact after veraison, contrary to many current hypotheses that veraison is associated with a general loss of membrane function and cellular compartmentation in the grape berry. We hypothesize that cell P is low in the PostV berry, and possibly other fleshy fruits, because of the presence of regulated quantities of apoplastic solutes.
欧亚葡萄浆果属于非跃变型果实，呈现双S型生长模式，在被称为“转色期”（即果实快速生长的第二个阶段开始之前）时，这些浆果会经历若干突然的生理变化。利用细胞压力探针检测了浆果发育过程中以及应对植物水分亏缺时中果皮细胞的原位膨压（P）。最初比较附着和分离浆果的试验表明，只要防止浆果失水，从藤蔓上分离后长达48小时内细胞膨压是稳定的。黎明前转色期前（PreV）的细胞膨压约为0.25兆帕，转色期后（PostV）降低了一个数量级至0.02兆帕。转色期前，细胞膨压从浆果表面开始随深度略有但显著下降，转色期后则不然。当盆栽藤蔓停止供水时，细胞膨压下降约0.2兆帕，黎明前藤蔓水势在12天内下降约0.6兆帕，而转色期后细胞膨压对黎明前藤蔓水势降低1.10兆帕完全不敏感。对受胁迫植物重新浇水，转色期前细胞膨压也会在24小时内恢复，但转色期后则不会。转色期前后细胞膨压的大幅下降与此时已知的浆果硬度下降相一致，转色期后膨压对藤蔓水分状况变化不敏感与当前的假说一致，即转色期后的浆果在水力上与藤蔓隔离。然而，转色期后果实中仍表现出约0.02兆帕的可测量膨压以及典型的细胞水力/渗透行为，这一事实表明转色期后果细胞膜仍保持完整，这与目前许多认为转色期与葡萄浆果中膜功能和细胞区室化普遍丧失有关的假说相反。我们推测，转色期后果实以及可能其他肉质果实中的细胞膨压低，是因为存在适量调控的质外体溶质。
