Selecting appropriate scion-rootstock combinations, which are determined by the rootstock’s root system, is vital for successful orchard management. There are usually two types of rootstocks available for pear orchards, clonal as well as seedling rootstocks. This research aimed to examine how seedlings and clonal rootstocks respond and withstand soil moisture limitations and drought stress conditions. Two pear rootstocks including ‘Dargazi’ seedlings and ‘Pyrodwarf’ clones were used. The irrigation treatments were well-watered (100% FC), moderate (60% FC), and severe drought (30% FC). The physiological and gas exchange responses were measured at 30 and 60 days after stress treatment (DAT). Results indicated that stomatal restrictions were one of the main causes of photosynthetic limitations under drought stress in the studied pear rootstocks. Photosynthesis (A_n) in ‘Pyrodwarf’ was more affected by the leaf ABA concentration than in ‘Dargazi’ rootstock. In 60 DAT, ‘Dargazi’ seedlings improved gas exchange parameters, and root dry weight (RDW). The increase in proline and glycine betaine and decrease in leaf water content per unit leaf area (LWCA) under drought stress showed signs of osmotic adjustment in both studied rootstocks. Although at 30 DAT, the photosynthetic restriction of ‘Pyrodwarf’ was affected by the stomatal closure, in 60 DAT the limitation to photosynthesis is maybe non-stomatal. In conclusion, these findings showed that ‘Pyrodwarf’ adapts better to moderate and shorter duration of drought stress, and ‘Dargazi’ was more adapted to severe and long periods of drought stress. This is due to the direct interaction of the rootstock and scion in resistance to drought stress. Besides it can help to select suitable rootstock for orchards faced with moderate to severe drought conditions.

Graphical Abstract

中文翻译：

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“Pyrodwarf”克隆和“Dargazi”幼苗梨 (Pyrus communis L.) 砧木对干旱胁迫的气体交换和生理反应不同

选择适当的接穗-砧木组合（由砧木的根系决定）对于成功的果园管理至关重要。梨园通常有两种类型的砧木，即无性系砧木和实生砧木。这项研究旨在研究幼苗和克隆砧木如何应对和承受土壤水分限制和干旱胁迫条件。使用了两种梨砧木，包括“Dargazi”幼苗和“Pyrodwarf”克隆。灌溉处理分为充分浇水（100% FC）、中度干旱（60% FC）和严重干旱（30% FC）。在应激治疗 (DAT) 后 30 天和 60 天测量生理和气体交换反应。结果表明，气孔限制是所研究的梨砧木在干旱胁迫下光合作用受限的主要原因之一。'Pyrodwarf' 中的光合作用 (A _n ) 比'Dargazi' 砧木更受叶片 ABA 浓度的影响。在 60 DAT 中，“Dargazi”幼苗改善了气体交换参数和根干重 ( RDW )。干旱胁迫下脯氨酸和甘氨酸甜菜碱的增加以及单位叶面积叶片含水量（LWCA ）的减少在两种研究的砧木中都显示出渗透调节的迹象。虽然在 30 DAT 时，'Pyrodwarf' 的光合作用限制受到气孔关闭的影响，但在 60 DAT 时，光合作用的限制可能是非气孔关闭的。总之，这些发现表明“Pyrodwarf”更好地适应中度和较短持续时间的干旱胁迫，而“Dargazi”更适应严重和长期的干旱胁迫。这是由于砧木和接穗在抵抗干旱胁迫方面的直接相互作用。此外，它还有助于为面临中度至重度干旱条件的果园选择合适的砧木。

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