Jupa Radek, Mészáros Martin, Hoch Günter, Plavcová Lenka
Department of Biology, Faculty of Science, University of Hradec Králové, Rokitanského 62, Hradec Králové CZ-500 03, Czech Republic.
Department of Technology, Research and Breeding Institute of Pomology, Research and Breeding Institute of Pomology, Holovousy 129, Hořice CZ-508 01, Czech Republic.
Tree Physiol. 2022 Feb 9;42(2):289-303. doi: 10.1093/treephys/tpab111.
The use of size-controlling rootstocks is central to modern high-density fruit production systems. While biological mechanisms responsible for vigor control are not fully understood, differences in water relations and carbohydrate storage ability have been suggested as two potential factors. To better understand the processes that control growth vigor, we analyzed the trunk radial variation at seasonal and diurnal timescales and measured the midday leaf water potential (ΨMD), leaf gas exchange and concentrations of non-structural carbohydrates (NSC) in apple trees of variety 'Jonagold' grafted on two rootstocks of contrasting growth vigor (dwarfing J-TE-G vs invigorating J-TE-H). The measurements were conducted during an exceptionally hot and dry summer. We found that smaller annual trunk radial increments in dwarfed trees were primarily due to an earlier cessation of trunk secondary growth. The interdiurnal trunk circumference changes (ΔC) were slightly lower in dwarfed trees, and these trees also had fewer days with positive ΔC values, particularly during the driest summer months. The trunks of dwarfed trees shrank gradually during the drought, showed less pronounced diurnal variation of trunk circumference and the maximum trunk daily shrinkage was only weakly responsive to the vapor pressure deficit. These results indicated that lower turgidity in the cambial region may have limited the trunk radial expansion in dwarfed trees during the hot and dry days. Dwarfed trees also maintained lower ΨMD and leaf gas exchange rates during the summer drought. These parameters decreased in parallel for both rootstock combinations, suggesting their similar drought sensitivity. Similar concentrations and seasonal dynamics of NSC in both rootstock combinations, together with their similar spring growth rates, suggest that NSC reserves were not directly limiting for growth. Our results support the prominent role of water relations in rootstock-induced size-controlling mechanisms and highlight the complexity of this topic.
使用控冠砧木是现代高密度水果生产系统的核心。虽然负责控制树势的生物学机制尚未完全了解，但水分关系和碳水化合物储存能力的差异被认为是两个潜在因素。为了更好地理解控制生长势的过程，我们分析了“乔纳金”品种苹果树在季节和昼夜时间尺度上的树干径向变化，并测量了嫁接在两种生长势差异较大（矮化砧木J-TE-G与乔化砧木J-TE-H）砧木上的苹果树的午间叶片水势（ΨMD）、叶片气体交换和非结构性碳水化合物（NSC）浓度。这些测量是在一个异常炎热干燥的夏季进行的。我们发现，矮化树较小的年树干径向增量主要是由于树干次生生长较早停止。矮化树的日间树干周长变化（ΔC）略低，并且这些树具有正ΔC值的天数也较少，特别是在最干燥的夏季月份。在干旱期间，矮化树的树干逐渐收缩，树干周长的昼夜变化不太明显，并且树干每日最大收缩对蒸汽压亏缺的响应较弱。这些结果表明，在炎热干燥的日子里，形成层区域较低的膨压可能限制了矮化树的树干径向扩展。在夏季干旱期间，矮化树还保持较低的ΨMD和叶片气体交换率。两种砧木组合的这些参数平行下降，表明它们具有相似的干旱敏感性。两种砧木组合中NSC的浓度和季节动态相似，以及它们相似的春季生长速率，表明NSC储备并非直接限制生长。我们的结果支持了水分关系在砧木诱导的控冠机制中的重要作用，并突出了该主题的复杂性。
