Fruit apoplast tension draws xylem water into mature sweet cherries
Fruit apoplast tension draws xylem water into mature sweet cherries
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DOI：
10.1016/j.scienta.2016.06.041
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发表时间：
2016-09-19
影响因子：
4.3
通讯作者：
Knoche, Moritz
中科院分区：
文献类型：
--
作者：
Winkler, Andreas;Brueggenwirth, Martin;Knoche, Moritz
甜樱桃果实雨裂可能与果实水分平衡有关。大多数关于水果水分平衡的研究都集中在通过果皮的水分转移（例如渗透流入，蒸腾流出）上，很少研究通过木质部和韧皮部维管系统的水流动。这里的目的是使用potometer和压力探针，研究木质部液流的果梗分离的树切在近端的水果+pedicel.Xylem水流入速率是恒定的，长达8小时，但随后放缓。压力探针确定了在花梗木质部中存在张力（负压）。木质部液流速率和木质部张力立即，完全和永久地消除，如果水果从花梗脱离。逐步去除切片的果肉开始在远端（花柱疤痕）和工作向近端（花梗）逐渐降低液流速率和紧张局势。花梗的长度只有一个边际流量的影响。果实质量和渗透压的果肉S形增加，在第二阶段（坑发展）和第三阶段（最终膨胀）的果实发育。流速和张力都增加到最大值，在早期阶段III，并在此后下降。流速和张力在类似于0%相对湿度（RH）下比在类似于100%RH下更高。在类似于0%和类似于100%RH的流速差在开发期间减小。果实在接近100%RH时的流量与浸水时的流量无差异。在早期发育过程中，木质部流量在花梗呈负相关的RH。随着发育的进行，木质部流动逐渐减少对RH的依赖。磨损角质层或削减皮肤没有影响木质部汁液流入。果肉压出液的渗透压与木质部的张力无相关性（r（2）= 0.13）。用增加渗透压的蔗糖溶液喂养花梗木质部的切割端，木质部流入量和张力降低到约2.5 MPa的渗透压。超过2.5 MPa时，仍可检测到一些流入和张力。结果表明，木质部流很可能是通过果实质外体的张力从树体进入果实的，这是由质外体到共质体的渗透水吸收和蒸腾作用引起的。少量的贡献可能是由于肉内的细胞壁肿胀。间接证据表明，木质部的电导率下降占第三阶段流量减少。这些发现使得木质部运输在果实开裂中起重要作用的可能性不太可能。(C)2016爱思唯尔B.V.保留所有权利。
Rain cracking of sweet cherry fruit (Prunus avium L) is likely related to fruit water balance. Most research on fruit water balance has focused on water transfers through the fruit skin (e.g. osmotic inflows, transpiration outflows)with little work on the water flows through the xylem and phloem vascular, systems of the pedicel. The objectives here were to use a potometer and a pressure probe to study xylem sap flows in the pedicels of fruit isolated from the tree by a cut at the proximal end of the fruit+pedicel.Xylem water inflow rates were constant for up to 8 h but then slowed. The pressure probe established the presence of a tension (a negative pressure) in the pedicel xylem. Xylem sap flow rates and xylem tensions were instantly, totally and permanently eliminated if the fruit was detached from the pedicel. Progressive removal of slices of the fruit flesh beginning at the distal end (stylar scar) and work towards the proximal end (pedicel) gradually decreased sap flow rates and tensions. The length of the pedicel had only a marginal effect on flows. Fruit mass and osmotic pressure of the flesh increased sigmoidally during stage II (pit development) and stage III (final swell) of fruit development. Flow rates and tensions both increased to maxima at early stage III, and both decreased thereafter. Flow rates and tensions were higher at similar to 0% relative humidity (RH) than at similar to 100% RH. The flow rate difference at similar to 0% and at similar to 100% RH decreased during development. There was no difference in flow rate of fruit at similar to 100% RH and fruit submerged in water. During early development, xylem flow in the pedicel was inversely related to RH. As development proceeded, xylem flow became progressively less dependent on RH. Abrading the cuticle or slashing the skin had no effect on xylem sap inflow. There was no relationship between the tension in the xylem and the osmotic pressure of the expressed juice of the flesh (r(2) = 0.13). Feeding the cut end of the pedicel xylem with sucrose solutions of increasing osmotic pressure decreased xylem inflow and tension up to osmoticpressures of about 2.5 MPa. Beyond 2.5 MPa, some inflow and tension remained detectable. The results establish that xylem flow is likely drawn into the fruit from the tree by apoplastic tension in the fruit, resulting from osmotic water uptake from apoplast to symplast and from transpiration. Minor contributions may result from cell wall swelling within the flesh. Indirect evidence suggests that decreased conductance of the xylem accounts for the decrease in flow during stage III. These findings render the possibility of a significant,role for xylem transport in fruit cracking unlikely. (C) 2016 Elsevier B.V. All rights reserved.