Australian Research Council Centre of Excellence in Plant Energy Biology, Research School of Biology, Building 134, The Australian National University, Canberra, ACT 2601, Australia; and Corresponding author. Email:
Australian Research Council Centre of Excellence for Translational Photosynthesis, Building 134, The Australian National University, Canberra, ACT 2601, Australia.
Funct Plant Biol. 2020 Mar;47(4):368-381. doi: 10.1071/FP19025.
Nitrogen availability and ontogeny both affect the relative growth rate (RGR) of plants. In this study of barley (Hordeum vulgare L.) we determined which growth parameters are affected by nitrate (N) availability, and whether these were confounded by differences in plant size, reflecting differences in growth. Plants were hydroponically grown on six different nitrate (N) concentrations for 28 days, and nine harvests were performed to assess the effect of N on growth parameters. Most growth parameters showed similar patterns of responses to N supply whether compared at common time points or common plant sizes. N had a significant effect on the biomass allocation: increasing N increased leaf mass ratio (LMR) and decreased root mass ratio (RMR). Specific leaf area (SLA) was not significantly affected by N. RGR increased with increasing N supply up to 1 mM, associated with increases in both LMR and net assimilation rate (NAR). Increases in N supply above 1 mM did not increase RGR as increases in LMR were offset by decreases in NAR. The high RGR at suboptimal N supply suggest a higher nitrogen use efficiency (biomass/N supply). The reasons for the homeostasis of growth under suboptimal N levels are discussed.
氮素供应和个体发育都会影响植物的相对生长率（RGR）。本研究以大麦（Hordeum vulgare L.）为材料，确定了哪些生长参数受硝酸盐（N）供应的影响，以及这些参数是否因植物大小的差异而混淆，反映了生长的差异。将植物在六种不同的硝酸盐（N）浓度下水培 28 天，并进行了九次收获，以评估 N 对生长参数的影响。无论在相同的时间点还是相同的植物大小进行比较，大多数生长参数对 N 供应的反应模式都相似。N 对生物量分配有显著影响：增加 N 会增加叶质量比（LMR），降低根质量比（RMR）。N 对比叶面积（SLA）没有显著影响。随着 N 供应的增加，RGR 增加，这与 LMR 和净同化率（NAR）的增加有关。在 1 mM 以上增加 N 供应不会增加 RGR，因为 LMR 的增加被 NAR 的降低所抵消。在亚最优 N 供应下高 RGR 表明更高的氮利用效率（生物量/N 供应）。讨论了在亚最优 N 水平下生长的自稳态的原因。
