Table_2_Spectroscopic Estimation of N Concentration in Wheat Organs for Assessing N Remobilization Under Different Irrigation Regimes.docx

Nitrogen (N) remobilization is a critical process that provides substantial N to winter wheat grains for improving yield productivity. Here, the remobilization of N from anthesis to maturity in two wheat cultivars under three irrigation regimes was measured and its relationship to organ N concentration was examined. Based on spectral data of organ powder samples, partial least squares regression (PLSR) models were calibrated to estimate N concentration (Nmass) and validated against laboratory-based measurements. Although spectral reflectance could accurately estimate Nmass, the PLSR-based Nmass-spectra predictive model was found to be organ-specific, organs at the top canopy (chaff and top three leaves) received the best predictions (R2 > 0.88). In addition, N remobilization efficiency (NRE) in the top two leaves and top third internode was highly correlated with its corresponding N concentration change (ΔNmass) with an R2 of 0.90. ΔNmass of the top first internode (TIN1) explained 78% variation of the whole-plant NRE. This study provides a proof of concept for estimating N concentration and assessing N remobilization using hyperspectral data of individual organs, which offers a non-chemical and low-cost approach to screen germplasms for an optimal NRE in drought-resistance breeding.

氮素再转运（N remobilization）是为冬小麦籽粒提供大量氮素以提升产量的关键生理过程。本研究测定了3种灌溉制度下2个小麦品种从扬花期至成熟期的氮素再转运过程，并探究了其与器官氮浓度的关联。基于器官粉末样品的光谱数据，本研究构建了偏最小二乘回归（PLSR）模型以估算氮质量浓度（Nmass），并以实验室实测数据对模型进行验证。尽管光谱反射率可较为精准地估算Nmass，但基于PLSR的Nmass-光谱预测模型存在器官特异性：冠层上部器官（颖壳及上部3片叶）的预测效果最优，决定系数（R²）大于0.88。此外，上部2片叶及上部第三节间的氮素转运效率（NRE）与其对应的氮质量浓度变化量（ΔNmass）呈高度相关，决定系数（R²）达0.90。上部第一节间（TIN1）的ΔNmass可解释全株NRE 78%的变异。本研究验证了利用单器官高光谱数据估算氮浓度、评估氮素再转运的可行性，为抗旱育种中筛选最优NRE的种质资源提供了一种无化学试剂、低成本的技术途径。