被动耐低磷杉木基因型P素内循环与根系皮层组织磷溶解的关系

Aimed at that Chinese fir genotype with low phosphorus toleration which was screened out in the early stage could save phosphorus consumption in root proliferation through enhancing internal recycle of phosphorus, applicants presented the hypothesis that phosphorus release in cortical tissue of root was the main P element resources in Chinese fir genotype with low phosphorus toleration. To test this hypothesis, based on the principle and method of Nutrition Genetics, Root Biology and Stress Botany, used Chinese fir genotype with low phosphorus toleration and Chinese fir genotype initiative to forage phosphorus as test materials, used devices with homogeneous phosphorus and heterogeneous supply, used isotope tracer technique with 32P, phosphorus supply in root, leaf and no phosphorus supply were set up. Through analysis technology of physiological processes in plant, space-time change rule of phosphorus flow, recycle and endogenous hormones in the tissues and organs were determined and analysed in Chinese fir genotype under different phosphorus supply. Change of root morphological and physiological indicators and phosphorus release law in cortex cells were researched in Chinese fir with different P useful efficiency. Relationship between phosphorus flow and recycle and phosphorus release in cortical tissue of root was discussed in Chinese fir genotype with low phosphorus toleration, which was expected to provide scientific basis for clarifying internal mechanism that Chinese fir genotype with low phosphorus toleration adapted to adversity, which may become a new disciplinary growing point. The research was of great significance for fully digging genetic potential of P useful efficiency and easing a fall in production of Chinese fir plantations.

针对课题组前期筛选出的被动耐低磷杉木基因型通过加快体内P素内循环来适应环境磷胁迫，以节约根系增生的磷消耗，申请者提出根系皮层组织的磷溶解是被动耐低磷杉木体内P素循环主要来源的假设。为验证这一假设，本项目根据营养遗传学、根系生物学和胁迫植物学的原理和方法，以被动耐低磷和主动觅磷杉木基因型为试验材料，利用均一性和异质性供磷装置，采用 32P同位素示踪技术，设置根系供磷、叶面供磷和不供磷处理，通过杉木生理过程分析技术，测定不同供磷处理杉木基因型组织器官中P素运转再利用、内源激素的时空变化规律，分析不同P高效利用杉木根系形态学和生理学指标变化及皮层细胞解体释磷规律，探讨被动耐低磷杉木基因型P素运转循环与根皮层组织解体磷溶解的关系，为阐明被动耐低磷杉木基因型适应磷胁迫逆境的内在机制提供科学依据，有望成为新学科生长点。这对于充分挖掘磷高效利用杉木体内P的潜能，缓解杉木人工林连栽生产力下降具有重要意义。

杉木（Cunninghamia lanceolata）为我国南方最重要的用材造林树种之一，但随着杉木人工林栽培面积不断增大及多代连栽现象的出现，加之南方林地因有效磷匮乏已严重制约了杉木人工林长期生产力的维持。鉴于筛选并利用高效利用土壤磷杉木基因型是缓解这一困境重要途径之一，项目组前期筛选出了2个P高效利用杉木基因型（主动觅磷杉木基因型主要通过在贫磷斑块中根系向四周拓展增生来适应环境磷胁迫；而被动耐低磷杉木基因型在贫磷斑块中的根系拓展不明显，主要通过加快体内P的内循环来抵抗磷胁迫逆境）。为进一步揭示杉木在低磷胁迫环境中如何平衡有效磷养分的吸收与消耗，以及被动耐低磷杉木基因型体内P利用分配特征与根系皮层组织溶解磷的关系，本项目选择被动耐低磷（36号/32号）和主动觅磷杉木基因型（25号）为研究对象，利用均一性和异质性供磷装置，研究发现：严重缺磷可导致杉木根系皮层通气组织（RCA）的形成，但36号杉木形成RCA明显多于25号，而且36号杉木苗高生长、叶生物量积累、以及茎和根的磷含量均明显高于25号，表现出根系成熟区RCA形成程度与根系P含量、平均直径和表面积增量呈显著负相关，而根系形态指标及地上部生物量、磷分配量呈显著正相关的规律。这是由于低磷胁迫下，被动耐低磷型杉木（32号）根系内积累大量脱落酸明显抑制了幼苗根系生长，且随着低磷胁迫时间的延长，杉木根系挥发物种类及含量逐渐减少，根系代谢消耗降低。可见，被动耐低磷杉木可通过诱导RCA形成、降低根系P含量和降低土壤探索的代谢成本，提高了体内P利用效率以抵抗低磷胁迫环境，为确证本项目提出的猜想提供可靠的科学依据。这对于充分挖掘杉木高效利用体内P 的潜能，缓解杉木人工林连栽生产力下降具有重要理论和实践意义。目前已发表了7篇标注国家自然科学基金资助的研究论文，其中SCI收录论文2篇；已获授权的相关专利7项；培养研究生6名。