Abstract
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.
Highlights
Wheat is one of the three major cereal crops providing over 700 million tons of grain worldwide per annual (FAO, 2019)
Chemical analysis in the laboratory showed that N concentration (Nmass) varied within and among different organs across all sampling time points (Figure 1B)
Nmass was observed with significant difference between leaf organs, while within internodes only TIN1 was significantly higher than the other internodes
Summary
Wheat is one of the three major cereal crops providing over 700 million tons of grain worldwide per annual (FAO, 2019). The high yield potential and grain quality in wheat are dependent on the uptake and utilization of nutrients, from which nitrogen (N) is a key composition of chlorophyll maintaining photosynthesis assimilates that determines the grain yield . Previous studies have demonstrated that around 60–90% of N in grains at maturity (Barbottin et al, 2005; White et al, 2016) is remobilized from vegetative organs in cereal crops. In wheat, this proportion could be as high as 95% (Kichey et al, 2007).
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