供锌水平和方式对山定子幼苗碳氮吸收及利用的影响

Effects of Zinc Supply Levels and Application Patterns on Carbon and Nitrogen Uptake and Utilization in Malus baccata. Seedlings

    摘要
  • 摘要:
    目的 通过评价不同供锌水平及方式对山定子幼苗光合作用、13C 同化与分配和 15N 吸收与利用的影响，探究锌对氮素吸收利用的影响机制，为苹果生产中氮肥利用率的提高和锌肥稳定供应奠定理论基础。
    方法 以苹果砧木山定子（Malus baccata.）幼苗为试材，研究沙培条件下处理周期为30天的5种供锌（Zn）处理方式（LZ: 处理期间持续供低Zn 0.015 mg L−1；LHZ: 先供低Zn 0.015 mg L−1 15 天，再供高Zn 5 mg L−1 15 天；AZ: 处理期间持续供适量Zn 0.3 mg L−1；HLZ: 先供高Zn 5 mg L−1 15 天，再供低Zn 0.015 mg L−1 15 天；HZ: 处理期间持续供高Zn 5 mg L−1）对幼苗根系形态结构、光合荧光参数、碳氮代谢相关酶活性、碳氮吸收和利用率的影响。
    结果 AZ处理幼苗生物量最高，根系形态结构最优，而LZ处理最弱。此外，该处理下叶片净光合速率、气孔导度、最大光化学效率（Fv/Fm）、二磷酸核酮糖羧化酶、硝酸还原酶及蔗糖磷酸合成酶活性均显著高于其他处理。同位素示踪结果表明13C积累量AZ处理最高，HLZ处理次之，LZ处理最低；15N吸收量和利用率均为AZ处理最高，HZ处理次之，LZ处理最低。供锌水平及方式对幼苗各器官13C与15N的分配率也有不同的影响。
    结论 不适宜的供锌水平和不稳定的供锌方式均阻碍了山定子幼苗生长、降低了氮素的吸收和利用，而适宜且稳定的供锌数量（0.3 mg L−1）增加了叶片光合作用，提高了叶片碳循环关键酶活性，促进植株对光合碳的固定，产生更多同化产物向根系运输，引起根系活力的提高和形态结构的改善，利于幼苗对氮素的吸收。

     

    Abstract:
    Objectives  The photosynthetic characteristics, 13C assimilation, 15N uptake and utilization of Malus baccata seedlings were evaluated under different zinc levels and application methods, aiming to provide a theoretical foundation for improving nitrogen nutrition and ensure a stable zinc supply in apple production.
    Methods Using seedlings of apple rootstock Malus baccata as experimental materials, this study investigated the effects of five zinc (Zn) supply treatments under sand culture conditions over a 30-day period. The treatments included: LZ, continuous supply of low Zn (0.015 mg L−1); LHZ, initial low Zn (0.015 mg L−1, 15 days) followed by high Zn (5 mg L−1, 15 days); AZ, continuous appropriate Zn (0.3 mg L−1); HLZ, initial high Zn (5 mg L−1, 15 days) followed by low Zn (0.015 mg L−1, 15 days); HZ, continuous high Zn (5 mg L−1). Parameters of root morphology, photosynthetic fluorescence parameters (Pn, gs, Fv/Fm), activities of carbon-nitrogen metabolism enzymes (Rubisco, NR, SPS), and isotopic tracing of 13C/15N allocation were analyzed.
    Results The AZ treatment yielded the highest seedling biomass and optimal root morphology, whereas LZ showed the lowest value. Under AZ, net photosynthetic rate (Pn), stomatal conductance (gs), PSII photochemical efficiency (Fv/Fm), and enzyme activities (Rubisco, NR, SPS) were significantly elevated. Isotopic tracing revealed that 13C accumulation peaked under AZ (HLZ > LZ), and 15N utilization efficiency was highest under AZ (HZ > LZ). Both Zn supply levels and application patterns differentially regulated 13C/15N allocation in seedling organs.
    Conclusions Both inappropriate zinc (Zn) supply levels and unstable Zn application patterns impaired seedling growth and nitrogen uptake. In contrast, appropriate and stable Zn supply levels enhanced net photosynthetic rate (Pn), increased the activity of key carbon metabolism enzymes, promoted carbon fixation in leaves, and enhanced the translocation of photosynthetic products. These improvements facilitated photo-assimilate transport to roots, improved root vitality, optimized root architecture, and enhanced seedling nitrogen uptake.

     

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