近年来,‘黄金梨’果实的果顶呈现细胞硬化,俗称‘铁头’‘硬头’‘黄头’‘绿头’,为生理病害。发病果实果肉失去应有的酥脆、多汁的口感。该研究分析了连续多年生长期易发生果顶“硬化症”的树与从未发生果顶“硬化症”的正常树的叶片和果实水势变化的差异,比较了2种类型果实中木质素含量、活性氧清除酶(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX))活性变化以及H_2O_2、丙二醛(MDA)含量等方面的差异。结果表明:与正常的‘黄金梨’树相比,易发病树的叶、果水势低,果实中的H_2O_2、MDA和木质素含量显著高于不发病树;易发病树的叶片水势与H_2O_2含量呈极显著负相关(r=-0.828 3,P<0.01),H_2O_2含量与MDA含量呈显著正相关(r=0.764 2,P<0.05);SOD活性显著低于不发病树;POD、CAT、APX的活性极显著高于不发病树。因此认为,发生果顶“硬化症”的树体或者结果部位可能由于存在一定程度的水分胁迫,导致了体内的活性氧产生与清除的动态平衡状态的变化,使H_2O_2、MDA过量生成和POD活性增加,从而促进了木质素的合成,这可能是导致近表皮薄壁细胞木质化的原因之一。 In recent years, the top of the fruit of ’Golden Pear’ presents cell harden, commonly known as ’hard head’, ’yellow head’ and ’green head’, which are physiological diseases. Fruiting fruit pulp should lose the crisp, juicy taste. This study analyzed the differences in water potential changes between leaves and fruits of normal trees that had been susceptible to fruit tops sclerosis in successive years of growth and that of normal trees that had never had fruit tops sclerosis. Lignin content, activities of active oxygen scavenging enzymes (SOD, POD, CAT, APX) and activities of H 2 O 2, Aldehyde (MDA) content and other aspects of the difference. The results showed that compared with the normal ’golden pear’ tree, the susceptible tree had low leaf and fruit water potential and H_2O_2, MDA and lignin contents in the fruit were significantly higher than those of the non-disease tree; leaf water potential and H_2O_2 content (R = -0.828 3, P <0.01). There was a significant positive correlation between H 2 O 2 content and MDA content (r = 0.764 2, P <0.05); SOD activity was significantly lower than that of non- APX activity was significantly higher than the non-diseased tree. Therefore, it is considered that the tree or fruit site with “top” scleroderma may be due to the existence of a certain degree of water stress, which leads to the change of the homeostasis state of active oxygen production and removal in vivo, POD activity increased, which promoted the synthesis of lignin, which may be one of the reasons leading to the near-epidermal parenchymal cells lignification.