Institute for Horticultural Production Systems, Leibniz-Universität Hannover, Hannover, Germany.
PLoS One. 2021 May 13;16(5):e0251351. doi: 10.1371/journal.pone.0251351. eCollection 2021.
Water movements through the fruit skin play critical roles in many disorders of strawberry (Fragaria × ananassa Duch.) such as water soaking, cracking and shriveling. The objective was to identify the mechanisms of fruit water loss (dry skin, transpiration) and water uptake (wet skin, osmosis). Fruits were held above dried silica gel or incubated in deionized water. Water movements were quantified gravimetrically. Transpiration and osmotic uptake increased linearly with time. Abrading the thin cuticle (0.62 g m-2) increased rates of transpiration 2.6-fold, the rates of osmotic uptake 7.9-fold. The osmotic potential of the expressed juice was nearly the same for green and for white fruit but decreased in red fruit stages. Fruit turgor was low throughout development, except for green fruit. There was no relationship between the rates of water movement and fruit osmotic potential. The skin permeance for transpiration and for osmotic uptake were both high (relative to other fruit species) but were two orders of magnitude greater for osmotic uptake than for transpiration. Incubating fruit in isotonic solutions of osmolytes of different sizes resulted in increases in fruit mass that depended on the osmolyte. The rate of osmotic uptake decreased asymptotically as molecular size of the osmolyte increased. When transpiration and osmotic uptake experiments were conducted sequentially on the same fruit, the rates of transpiration were higher for fruit previously incubated in water. Fluorescence microscopy revealed considerable microcracking in a fruit previously incubated in water. Our findings indicate that the high permeance for osmotic uptake is accounted for by an extremely thin cuticle and by viscous water flow through microcracks and along polar pathways.
水分通过果皮的运动在许多草莓（Fragaria × ananassa Duch.）紊乱中起着关键作用，例如水浸、开裂和皱缩。本研究旨在确定果实水分损失（干皮、蒸腾）和水分吸收（湿皮、渗透）的机制。将果实置于干燥硅胶上方或在去离子水中孵育。通过重量法定量水分运动。蒸腾和渗透吸收随时间呈线性增加。磨损薄的表皮（0.62 g m-2）使蒸腾速率增加 2.6 倍，渗透吸收速率增加 7.9 倍。绿果和白果的渗出液渗透压几乎相同，但红果阶段下降。除了绿果外，果实膨压在整个发育过程中都很低。水分运动速率与果实渗透压之间没有关系。蒸腾和渗透吸收的果皮渗透率都很高（相对于其他水果），但渗透吸收的渗透率比蒸腾高两个数量级。将果实在不同大小渗透溶质的等渗溶液中孵育会导致果实质量增加，这取决于渗透溶质。渗透吸收速率随渗透溶质分子量的增加而渐近下降。当在同一果实上依次进行蒸腾和渗透吸收实验时，先前在水中孵育的果实蒸腾速率更高。荧光显微镜显示，先前在水中孵育的果实存在大量微裂纹。我们的研究结果表明，高渗透吸收渗透率是由极薄的表皮和通过微裂纹和沿极性途径的粘性水流引起的。
