Grimm Eckhard, Hahn Jan, Pflugfelder Daniel, Schmidt Moritz Jonathan, van Dusschoten Dagmar, Knoche Moritz
1Abteilung Obstbau, Institut für Gartenbauliche Produktionssysteme, Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419 Hannover, Germany.
2Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany.
Hortic Res. 2019 Jun 22;6:79. doi: 10.1038/s41438-019-0161-3. eCollection 2019.
The so-called rain-cracking of sweet cherry fruit severely threatens commercial production. Simple observation tells us that cuticular microcracking (invisible) always precedes skin macrocracking (visible). The objective here was to investigate how a macrocrack develops. Incubating detached sweet cherry fruit in deionized water induces microcracking. Incubating fruit in DO and concurrent magnetic resonance imaging demonstrates that water penetration occurs only (principally) through the microcracks, with nondetectable amounts penetrating the intact cuticle. Optical coherence tomography of detached, whole fruit incubated in deionized water, allowed generation of virtual cross-sections through the zone of a developing macrocrack. Outer mesocarp cell volume increased before macrocracks developed but increased at a markedly higher rate thereafter. Little change in mesocarp cell volume occurred in a control zone distant from the crack. As water incubation continued, the cell volume in the crack zone decreased, indicating leaking/bursting of individual mesocarp cells. As incubation continued still longer, the crack propagated between cells both to form a long, deep macrocrack. Outer mesocarp cell turgor did not differ significantly before and after incubation between fruit with or without macrocracks; nor between cells within the crack zone and those in a control zone distant from the macrocrack. The cumulative frequency distribution of the log-transformed turgor pressure of a population of outer mesocarp cells reveals all cell turgor data followed a normal distribution. The results demonstrate that microcracks develop into macrocracks following the volume increase of a few outer mesocarp cells and is soon accompanied by cell bursting.
甜樱桃果实所谓的裂果现象严重威胁着商业生产。简单观察可知，表皮微裂纹（不可见）总是先于果皮大裂纹（可见）出现。此处的目的是研究大裂纹是如何形成的。将离体甜樱桃果实置于去离子水中孵育会引发微裂纹。在去氧水中孵育果实并同时进行磁共振成像表明，水分仅（主要）通过微裂纹渗透，完整表皮的渗透量检测不到。对置于去离子水中的离体完整果实进行光学相干断层扫描，能够生成通过正在形成的大裂纹区域的虚拟横截面。在大裂纹形成之前，外中果皮细胞体积增加，但此后以明显更高的速率增加。在远离裂纹的对照区域，中果皮细胞体积变化不大。随着水孵育持续进行，裂纹区域的细胞体积减小，表明单个中果皮细胞发生渗漏/破裂。随着孵育时间进一步延长，裂纹在细胞间扩展，形成一条长而深的大裂纹。有或没有大裂纹的果实孵育前后，外中果皮细胞膨压没有显著差异；裂纹区域内的细胞与远离大裂纹的对照区域内的细胞之间也没有差异。外中果皮细胞群体的对数转换膨压的累积频率分布表明，所有细胞膨压数据均呈正态分布。结果表明，微裂纹在少数外中果皮细胞体积增加后发展为大裂纹，且很快伴随着细胞破裂。
