Examination of the usability of leaf chlorophyll content and gene expression analyses as nitrogen status biomarkers in <i>Sorghum bicolor</i>

Sorghum [<i>Sorghum bicolor</i> (L.) Moench] has been receiving attention as a feedstock for biomass energy. Since nitrogen (N) significantly affects the plant biomass production, diagnosing the N status of sorghum during its growth would be significant. Therefore, in this study, we analyzed the changes in several physiological parameters of sorghum in response to N limitation, with the aim of identifying candidates of N status biomarkers in this species. Parameters responding early and sensitively to N deficiency were searched in hydroponically cultured seedlings, and their applicability to field conditions was examined. We found that the leaf chlorophyll content measured as a soil-plant analysis development (SPAD) value was promising as a candidate N status biomarker, as it showed responses consistent with N regimes in field conditions in multiple genotypes. A gene expression analysis was capable of detecting N deficiency sensitively at an early stage, although its application to practical situations requires further investigation to identify a suitable sets of marker genes.高粱[Sorghum bicolor (L.) Moench]作为生物质能源原料受到广泛关注。由于氮（N）对植物生物质产量具有显著调控作用，在高粱生长周期内诊断其氮素营养状况具备重要研究价值。本研究针对氮素限制条件下高粱的多项生理参数变化展开分析，旨在筛选该物种的氮素营养状况生物标志物候选对象。研究团队在水培培养的幼苗中筛选出对氮缺乏响应迅速且灵敏的参数，并验证其在田间条件下的适用性。结果发现，以土壤-植物分析发展（SPAD）值表征的叶片叶绿素含量有望成为候选氮素营养生物标志物，其在多个基因型的田间试验中均表现出与氮素处理方案一致的响应特征。此外，基因表达分析可在生长早期灵敏检测氮缺乏状况，但将其应用于实际生产场景仍需进一步筛选适配的标记基因集。