It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha?1(N1), 52.5 kg ha?1 (N2), 105 kg ha?1 (N3), 157.5 kg ha?1 (N4), and 210 kg ha?1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha?1), 1000 grain weight (39.7 g), grain yield (2.64 t ha?1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO2 content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields.
Compared with the standard method of manual fertilizer broadcasting (MFB), mechanized hill-drilling direct-seeding with deep application of slow-release nitrogen fertilizer (MHDDF) is an efficient method to integrate both fertilization and seeding. However, there are few studies that combine the use of slow-release fertilizer with MHDDF. We sought to explore the combined effect of MHDDF with slow-release fertilizer on rice yield and nitrogen, phosphorus, and potassium utilization, compared to MFB. We compared three different MHDDF methods (D30: 450 kg ha?1, D40: 600 kg ha?1, D50: 750 kg ha?1), with one MFB method (B50: 750 kg ha?1), and one control (CK: 0 kg ha?1). We found that the yield of all MHDDF method was higher than that of both the MFB method. Yield was the highest in the D50 treatment and was 14.14–46.03% higher than that in B50 treatment. Biomass accumulation, nutrient accumulation, and nutrient use efficiency were similarly higher in MHDDF method than both MFB and CK. Compared to B50, the D50 treatment increased nitrogen recovery efficiency by 170.53–231.50%, phosphorus recovery efficiency by 480.00–724.25%, and potassium recovery efficiency by 201.55–169.59%. Overall, we found that combining MHDDF with slow-release fertilizer was an effective method to increase rice yield and nutrient use efficiency compared with MFB.
Cymbidium is an orchid genus that has undergone rapid radiation and has high ornamental, economic, ecological and cultural importance, but its classification based on morphology is controversial. The plastid genome (plastome), as an extension of plant standard DNA barcodes, has been widely used as a potential molecular marker for identifying recently diverged species or complicated plant groups. In this study, we newly generated 237 plastomes of 50 species (at least two individuals per species) by genome skimming, covering 71.4% of members of the genus Cymbidium. Sequence-based analyses (barcoding gaps and automatic barcode gap discovery) and tree-based analyses (maximum likelihood, Bayesian inference and multirate Poisson tree processes model) were conducted for species identification of Cymbidium. Our work provides a comprehensive DNA barcode reference library for Cymbidium species identification. The results show that compared with standard DNA barcodes (rbcL + matK) as well as the plastid trnH-psbA, the species identification rate of the plastome increased moderately from 58% to 68%. At the same time, we propose an optimized identification strategy for Cymbidium species. The plastome cannot completely resolve the species identification of Cymbidium, the main reasons being incomplete lineage sorting, artificial cultivation, natural hybridization and chloroplast capture. To further explore the potential use of nuclear data in identifying species, the Skmer method was adopted and the identification rate increased to 72%. It appears that nuclear genome data have a vital role in species identification and are expected to be used as next-generation nuclear barcodes. 相似文献
Reproductive traits that function in pollinator attraction may be reduced or lost during evolutionary transitions from outcrossing to selfing. Although floral scent plays an important role in attracting pollinators in outcrossing species, few studies have investigated associations between floral scent variation and intraspecific mating system transitions. The breakdown of distyly to homostyly represents a classic example of a shift from outcrossing to selfing and provides an opportunity to test whether floral fragrances have become reduced and/or changed in composition with increased selfing. Here, we evaluate this hypothesis by quantifying floral volatiles using gas chromatography-mass spectrometry in two distylous and four homostylous populations of Primula oreodoxa Franchet, a perennial herb from SW China. Our analysis revealed significant variation of volatile organic compounds (VOCs) among populations of P. oreodoxa. Although there was no difference in VOCs between floral morphs in distylous populations as predicted, we detected a substantial reduction in VOC emissions and the average number of scent compounds in homostylous compared with distylous populations. A total of 12 compounds, mainly monoterpenoids and sesquiterpenoids, distinguished homostylous and distylous morphs; of these, (E)-β-ocimene was the most important in contributing to the difference in volatiles, with significantly lower emissions in homostyles. Our findings support the hypothesis that the transition from outcrossing to selfing is accompanied by the loss of floral volatiles. The modification to floral fragrances in P. oreodoxa associated with mating system change might occur because high selfing rates in homostylous populations result in relaxed selection for floral attractiveness. 相似文献
A series of plasmids were constructed to examine the effects of p19 and orf1‐orf2 genes from Bacillus thuringiensis on Cyt1Aa synthesis and inclusion formation. The plasmids expressed the cyt1Aa gene along with either p19 or orf1‐orf2, or each of them coordinatively with p20 in the acrystalliferous strain of B. thuringiensis subsp. israelensis 4Q7. No effect on the expression of Cyt1Aa protein was found when P19 or Orf1‐Orf2 co‐expressed with Cyt1Aa. However, when including p20 gene, the constructs with p19 or orf1‐orf2 gene produced lower yield of Cyt1Aa proteins than without p19 or orf1‐orf2 gene. Electron microscopy observation and bioassay showed that P19 and Orf1‐Orf2 have no influence on the crystal size and toxicity of Cyt1Aa protein. It is presumed that P19 and Orf1‐Orf2 might have negative effects on Cyt1Aa synthesis in B. thuringiensis.相似文献
The Weibull model is a flexible growth model that describes both general population growth and plant disease progress. However, lack of an asymptotic parameter has limited its wider application. In the present study, an asymptotic parameter K was introduced into the original Weibull model, written as; y = K {1 − exp [− ( t − a ) c ]}, in which a , b , c and K are location, scale, shape, and asymptotic parameters, respectively, y is the proportion of disease and t is time. A wide range of simulated disease progress data sets were generated using logistic, Gompertz and monomolecular models by specifying different parameter values, and fitted to both original and modified Weibull models. The modified model provided statistically better fits for all data than the original model. The modified model can thus improve the curve-fitting ability of the original model which often failed to converge, especially when the asymptote is less than 1.0. Actual disease progress data on wheat leaf rust and tomato root rot with different asymptotic values were also used to compare the original and modified Weibull models. The modified model provided a statistically better fit than the original model, and model estimates of asymptotic parameter K were nearly identical to the actual disease maxima reflecting the characteristics of the host-pathosystem. Comparison of logistic, Gompertz, and Weibull models including parameter K by fitting to the observed data on wheat leaf rust and tomato root rot revealed the applicability of the modified Weibull model, which in a majority of cases provided a statistically superior fit. 相似文献