不同梨砧木对缺铁胁迫的生理响应差异研究

Difference in physiological response of different pear rootstocks under iron deficiency stress

【目的】旨在通过探究缺铁胁迫下不同梨砧木幼苗体内铁分配规律及有机酸种类和含量的差异,为培育铁高效利用梨砧木提供理论依据。【方法】以三种不同梨砧木,杜梨Ⅰ(湖北杜梨HB-Pyrus betulaefolia)、杜梨Ⅱ(郑州杜梨ZZ-Pyrus betulaefolia)、山梨(黑龙江山梨HS-Pyrus ussuriensis)幼苗为试材,进行水培试验。以Hogland营养液为基础,在其他养分含量不变的情况下,设两个Fe水平1和40μmol/L,分别代表缺铁胁迫和正常供铁。在砧木幼苗培养21天后,测定了幼苗活性铁和全铁元素含量、根系构型及各部位不同种类有机酸的含量。【结果】缺铁胁迫下,杜梨Ⅰ茎叶中活性铁/全铁比例是杜梨Ⅱ的2.80倍和2.94倍,是山梨的3.29倍和2.05倍,其叶中的活性铁和全铁积累量分别达到15.71 mg/plant和78.82 mg/plant。缺铁胁迫下,杜梨Ⅱ和山梨的倒一叶叶绿素含量下降幅度显著高于杜梨Ⅰ。三种梨砧木幼苗体内柠檬酸含量最高,其次是苹果酸,这两种酸占有机酸总量的74.8%以上。与正常供铁相比,缺铁胁迫下山梨根和叶中苹果酸含量提高了4.70和1.69倍,分别达到0.96 mg/g和4.80 mg/g,显著高于杜梨Ⅰ和杜梨Ⅱ,而杜梨根和叶中的柠檬酸含量较高,尤其是杜梨Ⅰ品种,达到4.02 mg/g和11.98 mg/g。【结论】三种梨砧木对铁的吸收和运输存在较大差异。杜梨Ⅰ根系吸收能力较强,根和叶中活性铁含量及积累量均较高,因而耐缺铁。缺铁胁迫下,两种杜梨根系中主要合成柠檬酸而山梨主要合成苹果酸,可能是山梨对缺铁敏感的机制之一。

【Objectives】The study was aimed to provide theoretical bases for breeding high Fe use efficiency cultivar by comparing the difference in Fe distribution and content of organic acid in pear rootstocks under Fe deficiency.【Methods】A hydroponic experiment was carried out with three cultivars, which were HB-Pyrus betulaefolia（HB-Ⅰ）, ZZ-Pyrus betulaefolia（ZZ-Ⅱ） and HS-Pyrus ussuriensis（HS） supplied by 1 μmol/L Fe NaEDTA and 40 μmol/L Fe Na-EDTA. After 21 days, the characteristic of root architecture and the content of active Fe, total Fe and organic acids in each part of pear rootstocks were determined.【Results】Under iron deficiency stress, the active iron and total iron accumulation in the leaves of HB-Ⅰ were 15.71 and 78.82 mg/plant, the distribution ratios of active and total Fe in stems and leaves were 2.80 and 2.94 times of those in ZZ-Ⅱ and 3.29 and 2.05 times of those in HS, respectively. The chlorophyⅡcontents in the first leaf from the top of both ZZ-Ⅱand HS were all significantly higher than that of HB-I. The content of citric acid was the highest in three kinds of pear rootstocks, followed by malic acid, and they accounted for 74.8% of total organic acid content in the three pear stocks. The malic acid contents in roots and leaves of HS under iron deficiency were 0.96 and 4.80 mg/g,respectively, which were 4.70 and 1.69 times of those under normal iron treatment and were significantly higher than those in both HB-Ⅰ and ZZ-Ⅱ. In the roots and leaves of HB-Ⅰ and ZZ-Ⅱ, the citric acid contents were relatively higher than other organic acids, especially in HB-I, reaching 4.02 and 11.98 mg/g.【Conclusions】The absorption and transportation of iron in the three cultivars of pear rootstocks were physiologically different. The root absorption capacity of Pyrus betulaefoliaⅠ was relatively better, and content and accumulation of active iron in root and leaves were relatively higher. As compared with other varieties, Pyrus betulaefoliaⅠ was nonsusceptible to iron deficiency. Under iron deficiency stress, the root of Pyrus ussuriensis mainly synthesized malic acid, while the root of Pyrus betulaefolia mainly synthesized citric acid, which suggested one of the mechanisms for their different responses to iron deficiency.