No abstract

Lindera, a core genus of the Lauraceae family, has important economic uses in eastern Asia and North America. However, its historical diversification has not been clarified. In this study, we report nine newly sequenced Lindera plastomes. The plastomes of these nine Lindera species range from 152,211 (L. nacusua) to 152,968 bp (L. metcalfiana) in length, similar to that of another Lauraceae species, Litsea glutinosa (152,618 bp). The length variation of these plastomes derived from the length variation in the loci ycf1, ycf2, ψycf1, and ndhF-ψycf1. Comparing our sequences with other available plastomes in the Lauraceae indicated that eight hypervariable loci, ihbA-trnG, ndhA, ndhF-rpl32, petA-psbJ, psbK-psbI, rps16, trnS-trnG, and ycf1, could serve as DNA barcodes for species delineation, and that the inverted repeats (IRs) showed contraction/expansion. Further phylogenetic analyses were performed using 32 complete plastomes of Lauraceae and seven barcodes from 14 additional species of Lindera and related species in the core Lauraceae. The results showed that these Lindera species grouped into two or four sub-clades, and that two Litsea species and Laurus nobilis were located in the same sub-clade as five Lindera species. These data support a close relationship between the genera Laurus, Lindera, and Litsea, and suggest that Lindera is polyphyletic.

Accurate forecasting of N required for plant growth can help optimize grain yields, farm profits, and N use efficiency and reduce the risk of environmental pollution. The objectives of this study were to: (i) establish a critical N (Nc) dilution curve for winter wheat (Triticum aestivum L.) based on the leaf area index (LAI), (ii) compare this curve with Nc dilution curves for winter wheat that are based on plant dry matter, and (iii) assess the plausibility of using this new curve to estimate the N status of winter wheat. Four field experiments were conducted with different N application rates. Twenty plants from each plot were sampled from the Feekes 3 to the Feekes 10.5 stage for growth analysis. The relationship between Nc and LAI could be described by a negative power equation, Nc = 4.06LAI −0.4, when the LAI values were in the range of 1.4 to 7.5. For LAI values <1.4, however, the constant value Nc = 3.58% was used. The N nutrition index (NNI) ranged from 0.34 to 1.31 during the vegetative stage under different N application rates from 2009 to 2011. There was a significant positive relationship between differences in NNI and differences in N application rates across four wheat development stages. Validation of the models with independent data produced a root mean squared error of 28 kg ha−1. The Nc dilution curve identified limiting and nonlimiting wheat N status and could be used as a reliable indicator of in‐season N stress of wheat grown in eastern China.

Various sensors have been used to obtain the canopy spectral reflectance for monitoring above-ground plant nitrogen (N) uptake in winter wheat. Comparison and intercalibration of spectral reflectance and vegetation indices derived from different sensors are important for multi-sensor data fusion and utilization. In this study, the spectral reflectance and its derived vegetation indices from three ground-based sensors (ASD Field Spec Pro spectrometer, CropScan MSR 16 and GreenSeeker RT 100) in six winter wheat field experiments were compared. Then, the best sensor (ASD) and its normalized difference vegetation index (NDVI (807, 736)) for estimating above-ground plant N uptake were determined (R2 of 0.885 and RMSE of 1.440 g·N·m−2 for model calibration). In order to better utilize the spectral reflectance from the three sensors, intercalibration models for vegetation indices based on different sensors were developed. The results indicated that the vegetation indices from different sensors could be intercalibrated, which should promote application of data fusion and make monitoring of above-ground plant N uptake more precise and accurate.