Casagrande Biasuz Erica, Kalcsits Lee A
Department of Horticulture, Washington State University, 1100 North Western Avenue, Wenatchee, WA 98801, USA.
AoB Plants. 2022 May 5;14(4):plac020. doi: 10.1093/aobpla/plac020. eCollection 2022 Aug.
Composite trees combine optimal traits from both the rootstock and the scion. Dwarfing rootstocks are commonly used to reduce shoot vigour and improve fruit quality and productivity. Although growth habits of different rootstocks have been clearly described, the underlying physiological traits affecting scion vigour are not well understood. Plant water status and stem water potential are strongly influenced by water supply and demand through the soil-plant-atmosphere continuum. In the scion, stomata regulate water loss and are essential to prevent hydraulic failure. Stomatal conductance influences leaf carbon isotope composition. Combined, the effects of reduced stomatal conductance and, consequently, carbon fixation may affect tree growth. These differences could also correspond to differences in scion vigour controlled by rootstock genotype. Here, vegetative growth, gas exchange, stem water potential and leaf δC were compared to determine how rootstocks affect scion water relations and whether these differences correspond to shoot vigour. There was a range in vigour among rootstocks by almost 2-fold. Net leaf carbon assimilation rates were lower in rootstocks with lower vigour. Rootstock vigour was closely associated with leaf gas exchange and stem water potential in the scion and was reflected in leaf δC signatures. Dwarfing was strongly affected by changes to plant water status induced by rootstock genotype and these changes are distinguishable when measuring leaf and stem δC composition. These observations indicate that scion water relations and leaf carbon isotope discrimination were affected by rootstock genotype. These results have implications for better understanding dwarfing mechanisms in apple rootstocks and the relationship with water-use traits.
复合树结合了砧木和接穗的最佳特性。矮化砧木通常用于降低枝条活力，提高果实品质和产量。尽管不同砧木的生长习性已有明确描述，但影响接穗活力的潜在生理特性仍未得到充分了解。植物水分状况和茎水势通过土壤-植物-大气连续体受到水分供应和需求的强烈影响。在接穗中，气孔调节水分流失，对于防止水力故障至关重要。气孔导度影响叶片碳同位素组成。综合起来，气孔导度降低以及由此导致的碳固定效应可能会影响树木生长。这些差异也可能对应于由砧木基因型控制的接穗活力差异。在此，比较了营养生长、气体交换、茎水势和叶片δC，以确定砧木如何影响接穗水分关系，以及这些差异是否与枝条活力相对应。砧木之间的活力范围相差近2倍。活力较低的砧木中净叶片碳同化率较低。砧木活力与接穗中的叶片气体交换和茎水势密切相关，并反映在叶片δC特征中。矮化受到砧木基因型引起的植物水分状况变化的强烈影响，在测量叶片和茎的δC组成时，这些变化是可区分的。这些观察结果表明，接穗水分关系和叶片碳同位素歧视受砧木基因型影响。这些结果对于更好地理解苹果砧木的矮化机制以及与水分利用特性的关系具有重要意义。
