Wada Hiroshi, Matthews Mark A, Shackel Ken A
Department of Viticulture and Enology, University of California, Davis, CA 95616-8683, USA.
J Exp Bot. 2009;60(6):1773-81. doi: 10.1093/jxb/erp050.
Using a novel pressure membrane (PM) apparatus for the extraction of apoplastic fluid from field-grown grape (Vitis vinifera L.) berries, our hypothesis that significant apoplast solutes accumulate at the beginning of the ripening process (i.e. veraison), and that this accumulation might contribute to progressive berry softening due to a progressive loss of mesocarp cell turgor pressure (P) was tested. It was necessary to correct the solute potential (Psi(s)) of fluid collected with the PM for dilution due to the presence of a dead volume in the apparatus, but after correction, the Psi(s) obtained with the PM agreed with that obtained by low speed centrifugation. A clear decline in fruit apoplastic solute potential (psi(S)(A)) began approximately 10 d prior to fruit coloration, and it was found to be coincident with a decline in mesocarp cell P and fruit elasticity (E). By late in fruit development when berry growth ceased (90 d after anthesis), both apoplast and fruit Psi(s) reached almost -4 MPa. These results support the hypothesis that a decrease in psi(S)(A) is responsible for the observed loss in mesocarp cell P, and is the mechanistic cause of berry softening.
我们使用一种新型压力膜(PM)装置从田间种植的葡萄(Vitis vinifera L.)浆果中提取质外体汁液,对我们的假设进行了验证,即质外体溶质在成熟过程开始时(即转色期)大量积累,并且这种积累可能由于中果皮细胞膨压(P)的逐渐丧失而导致浆果逐渐软化。由于该装置中存在死体积,有必要对用PM收集的汁液的溶质势(Ψs)进行稀释校正,但校正后,用PM获得的Ψs与通过低速离心获得的结果一致。果实质外体溶质势(ψS(A))在果实着色前约10天开始明显下降,并且发现它与中果皮细胞P和果实弹性(E)的下降同时发生。在果实发育后期,当浆果生长停止时(开花后90天),质外体和果实的Ψs几乎都达到-4 MPa。这些结果支持了以下假设:ψS(A)的降低是观察到的中果皮细胞P丧失的原因,并且是浆果软化的机制原因。