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影响，在高粱生长过程中诊断其氮素状况具有重要研究价值。为此，本研究分析了高粱在氮限制条件下多项生理参数的变化，旨在鉴定该物种氮素状况生物标志物的候选靶标。研究团队在水培培养的幼苗中筛选出对氮缺乏呈现早期且灵敏响应的参数，并考察了这些参数在田间条件下的适用性。结果发现，以土壤-植物分析发展（soil-plant analysis development，SPAD）值表征的叶片叶绿素含量，具备成为氮素状况生物标志物候选的潜力，因其在多个基因型的田间条件下均表现出与氮素处理模式一致的响应特征。基因表达分析能够在早期阶段灵敏检测氮缺乏状况，尽管其实际应用仍需进一步研究以确定一套合适的标记基因集。