Abstract Soil acidification is a worldwide problem and adoption of acid-tolerant rootstocks is an essential strategy to face this challenge in order to maintain the production of citrus. In the present study, seedlings of five genotypes of citrus rootstocks including KPJ-020 (Citrus depressa Hayata ‘Shiikuwasha’), KPJ-007 (C. reticulata Blanco), KPJ-010 (C. daoxinensis Blanco), Carrizo (C. sinensis × Poncirus trifoliata) and ZYXC (C. junos Siebold Tanaka) were used as testing materials and subjected to 10, 30 and 60 days treatment with nutrient solutions at pH2.5, 3.5, 4.5 and 6.0 (control), respectively, to evaluate their tolerance to acidic stress. Symptoms of leaf damage, relative electrical conductivity (REC), the content of chlorophyll, soluble sugar (SS), soluble protein, proline, malondialdehyde (MDA), and the activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaves were examined at different period time of treatment. Acidic stress caused symptoms of chlorosis on leaves due to reduced content of chlorophyll pigments. Analysis of physiological and biochemical parameters indicated that both physiological and biochemical processes of plants were significantly affected by acidic stress. Lower pH decreased the accumulation of N, P, K, Ca, Mg and B, but increased the accumulation of S, Fe, Zn, Mn and Cu. Principal component analysis based on the nine parameters was performed in order to comprehensively evaluate the acidic tolerance of rootstocks. The degree of acid tolerance significant varied within the rootstocks. ZYXC and KPJ-020 showed better tolerance than other rootstocks. Analysis of orthogonal experiment results revealed that the influence of the factors in the treatment to acidic tolerance varied among different rootstocks. In KPJ-020, the duration of treatment was the main factor affecting the tolerance, but the strength of acidic stress was the main factor determining the tolerance of ZYXC, as well as other three rootstocks. This suggested that the mechanisms of acidic tolerance were probably different between the two tolerant genotypes of rootstocks of ZYXC and KJP-020. The former possesses the tolerance by maintaining the capability to uptake mineral nutrients under acidic stress, while the latter has better ability to adapt to lower pH conditions.

中文翻译：

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5种柑橘砧木对酸胁迫的不同耐受性和不同响应的主成分分析和正交分析

摘要 土壤酸化是一个世界性问题，采用耐酸砧木是应对这一挑战以维持柑橘生产的重要策略。在本研究中，五种基因型柑橘砧木的幼苗包括 KPJ-020 (Citrus depressa Hayata 'Shiikuwasha')、KPJ-007 (C. reticulata Blanco)、KPJ-010 (C. daoxinensis Blanco)、Carrizo (C. sinensis) × Poncirus trifoliata) 和 ZYXC (C. junos Siebold Tanaka) 作为试验材料，分别用 pH2.5、3.5、4.5 和 6.0（对照）的营养液处理 10、30 和 60 天，以评估其对酸性胁迫的耐受性。叶片损伤症状、相对电导率（REC）、叶绿素含量、可溶性糖（SS）、可溶性蛋白、脯氨酸、丙二醛（MDA）、检测不同处理时间叶片中超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的活性。由于叶绿素色素含量减少，酸性胁迫导致叶片出现萎黄症状。生理生化参数分析表明，植物的生理生化过程都受到酸性胁迫的显着影响。较低的 pH 值降低了 N、P、K、Ca、Mg 和 B 的积累，但增加了 S、Fe、Zn、Mn 和 Cu 的积累。为了综合评价砧木的耐酸性，基于9个参数进行主成分分析。砧木内的耐酸程度存在显着差异。ZYXC 和 KPJ-020 表现出比其他砧木更好的耐受性。正交试验结果分析表明，不同砧木处理中各因素对耐酸性的影响存在差异。在KPJ-020中，处理时间是影响耐性的主要因素，但酸性胁迫强度是决定ZYXC以及其他三种砧木耐性的主要因素。这说明ZYXC和KJP-020这两种砧木耐酸基因型的耐酸机制可能不同。前者通过在酸性胁迫下保持吸收矿质养分的能力而具有耐受性，而后者具有更好的适应较低pH条件的能力。处理时间长短是影响耐性的主要因素，但酸性胁迫强度是决定ZYXC以及其他3种砧木耐性的主要因素。这说明ZYXC和KJP-020这两种砧木耐酸基因型的耐酸机制可能不同。前者通过在酸性胁迫下保持吸收矿质养分的能力而具有耐受性，而后者具有更好的适应较低pH条件的能力。处理时间长短是影响耐性的主要因素，但酸性胁迫强度是决定ZYXC以及其他3种砧木耐性的主要因素。这说明ZYXC和KJP-020这两种砧木耐酸基因型的耐酸机制可能不同。前者通过在酸性胁迫下保持吸收矿质养分的能力而具有耐受性，而后者具有更好的适应较低pH条件的能力。