Since the early 2000s, Persian oak forests in the Zagros in Iran have shown signs of decline. This study was designed to determine the relationships between crown dieback of Persian oak (Quercus brantii) with morphological and physiological leaf traits in two forest sites: Sheshdar (SH) and Gatchan (GA) in Ilam, Western Iran. Trees with increasing severity of crown dieback were selected from healthy to severely defoliated. Foliage samples were taken randomly from the crown on the slope‐aspect of the site. The results suggested that Q. brantii was not sensitive to drought effects during normal growth processes. There were variations in leaf physiological traits, however, in the different dieback classes at both sites. Foliage from declining trees at both sites had higher dry weights in contrast to the decreasing water contents associated with lower leaf areas in trees with severe defoliation from site GH. Chlorophyll pigments (Chl a and b) and carotene (Car.) were significantly lower decreased significantly in trees with moderate to severe defoliations from site GH, while in leakage from the foliage increased. A contrasting pattern occurred at site SH as accumulations of osmotic solutes (soluble sugars, total soluble protein and proline) increased significantly in foliage of severely defoliated trees, while at site GH, the total soluble protein and proline contents showed an upward trend until moderate defoliation. It was concluded that the physiological responses of Persian oak trees with dieback varied under extreme drought. Based on principal component analysis, leaf water status contributed most to the differences between dieback groups. It is concluded that physiological variations in oak foliage contribute to defence mechanisms enabling drought to be tolerated, maintaining essential life processes.

中文翻译：

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响应于波斯栎（Quercus brantii Lindl。）冠层枯萎的叶片形态和生理变化

自2000年代初以来，伊朗扎格罗斯的波斯橡树林已显示出衰退的迹象。这项研究旨在确定伊朗西部伊兰（Shelam）的Sheshdar（SH）和Gatchan（GA）这两个林区的波斯栎（Quercus brantii）冠冠枯萎与形态和生理叶片性状之间的关系。从健康到严重落叶的树冠严重度增加的树木都被选出。从该地点的坡度上从树冠上随机采集叶子样本。结果表明，Q。brantii对正常生长过程中的干旱影响不敏感。但是，在两个部位的不同的枯萎病类别中，叶片的生理特性均存在差异。与位置GH严重脱叶的树木中，较低的水分含量与较低的叶面积相关联的水分形成鲜明对比，这两个位置的树木均从下降的叶片中获得较高的干重。叶绿素色素（Chl a和b）和胡萝卜素（Car。）显着降低，从中点GH到中度至重度脱叶的树木显着降低，而从叶面渗漏的叶绿素增加。在严重脱叶的树木叶片中，渗透性溶质（可溶性糖，总可溶性蛋白和脯氨酸）的积累显着增加，在SH部位出现了相反的模式，而在GH部位，总可溶性蛋白和脯氨酸含量呈上升趋势，直至中度脱叶。得出的结论是，在极度干旱条件下，波斯栎树的凋零生理反应有所不同。基于主成分分析，叶片水分状况是导致枯萎病群体之间差异的最大原因。结论是橡树叶中的生理变化有助于防御机制，使干旱得以忍受，并维持生命的基本过程。