Proper management of irrigation and nitrogen-application increases crop N-uptake efficiency and reduces nitrate leaching

Irrigation is, on one hand, expected to increase the risk of nitrate leaching through increased rates of percolation, but, on the other hand, enhances plant nutrient uptake and growth, thereby limiting the risk of leaching. To investigate this dichotomy, we analysed the effects of irrigation at three nitrogen (N)-application rates in spring barley (Hordeum distichum L., two experiments with 50, 100, and 150 kg N ha(-1)) and winter oilseed rape (Brassica napus L., one experiment with 50, 150, and 250 kg N ha(-1)) on a coarse sandy soil in Denmark in a humid climate, which facilitates nitrate leaching. Analyses comprised grain/seed dry matter yield, N-uptake, nitrogen use efficiency (partial nitrogen budget, PNB, and partial-factor productivity, PFP) and nitrate leaching. For both crops, increasing N-application without consideration of the crops' drought-stress responses lead to a relatively lower N-uptake in grain, lower yield, lower PNB and PFP and higher nitrate leaching, although responses were not proportionally to increasing N-application. The effect of irrigation at the lowest N-rates was limited. The non-irrigated treatments with the highest N-rates had a grain/seed yield of 3.2, 2.3 and 0.7 t ha(-1) and nitrate leaching rates of 64, 72 and 127 kg N ha(-1) compared to a grain/seed yield of 5.3, 5.0 and 2.6 kg N ha(-1) and nitrate leaching rates of 61, 42 and 85 kg N ha(-1) (for spring barley, spring barley and winter oilseed rape, respectively). These results show that synchronised management of both irrigation and N-application are essential for reducing the risk of nitrate leaching and to promote efficient crop N-uptake in periods of droughts

Seed Production of Red Clover (Trifolium pratense L.) under Danish Field Conditions

High and stable seed yield is critical for red clover (Trifolium pratense L.) seed production and the commercial exploitation of the crop. A three-year experiment was conducted from 2013 to 2015 under Danish field conditions to explore the influence of precipitation during peak flowering on the seed yield of three red clover cultivars. We investigated the flowering duration and intensity based on a visual scale assessment, seed yield, and thousand seed weight in all three experimental years. In 2014 and 2015 we measured the seed yield components of floret number per flower head, seed number per flower head, and seed set. During the experimental period, high seed yields of more than 1000 kg ha−1 were obtained for the diploid cultivars ‘Rajah’ and ‘Suez’. Although a relatively high seed yield of 500 kg ha−1 was obtained in the tetraploid cultivar ‘Amos’, this was only around half of the seed yield and seed set of the diploid cultivars. Precipitation during peak flowering positively influenced the seed yield and thousand seed weight for the three cultivars. We conclude that observations of flowering phenology are required to determine the impact of environmental conditions on seed yield in red clover cultivars. Further, adequate water supply during peak flowering is important to obtain the high seed yield of red clover

Pollination and Plant Reproductive Success of Two Ploidy Levels in Red Clover (<i>Trifolium pratense</i> L.)

Plant reproduction in red clover requires cross-fertilization via insect pollination. However, the influences of visitation rate and timing on maximizing ovule utilization are yet to be determined. We aimed to study the influences of visitation rate, flowering stage, and self-incompatibility on reproductive success. We applied hand and honey bee pollination in the study of eight red clover cultivars with two ploidy levels released between 1964 and 2001. In hand pollination, increasing the visitation rates (from 10 to 80 pollinated florets per flower head) increased the seed number per flower head but reduced the seed number per pollinated floret. Different flowering stages (early, middle, and full flowering) did not influence the seed number per pollinated floret significantly. There was a marked difference in reproductive success depending on the ploidy level, with 0.52 seeds per pollinated floret in diploid and 0.16 in tetraploid cultivars. During the cultivar release history, seed number per pollinated floret seemed to decrease in diploid cultivars, whereas it increased in tetraploids. In honey bee pollination, diploid cultivars had more two-seeded florets than tetraploids. Different visitation rates and the stochastic nature of pollen transfer resulted in difficulties when the plant reproductive success between hand and bee pollination was compared. A maximum of 0.27 seeds per pollinated floret were produced in hand pollination compared to the 0.34 in honey bee pollination. In spite of this, hand pollination provided a valuable method for studying the pollination biology and reproduction of red clover. Future studies may employ hand pollination to unravel further aspects of the low reproductive success with the future perspective of improving seed number per pollinated floret in tetraploid red clover

Proper management of irrigation and nitrogen-application increases crop N-uptake efficiency and reduces nitrate leaching

Irrigation is, on one hand, expected to increase the risk of nitrate leaching through increased rates of percolation, but, on the other hand, enhances plant nutrient uptake and growth, thereby limiting the risk of leaching. To investigate this dichotomy, we analysed the effects of irrigation at three nitrogen (N)-application rates in spring barley (Hordeum distichum L., two experiments with 50, 100, and 150 kg N ha−1) and winter oilseed rape (Brassica napus L., one experiment with 50, 150, and 250 kg N ha−1) on a coarse sandy soil in Denmark in a humid climate, which facilitates nitrate leaching. Analyses comprised grain/seed dry matter yield, N-uptake, nitrogen use efficiency (partial nitrogen budget, PNB, and partial-factor productivity, PFP) and nitrate leaching. For both crops, increasing N-application without consideration of the crops’ drought-stress responses lead to a relatively lower N-uptake in grain, lower yield, lower PNB and PFP and higher nitrate leaching, although responses were not proportionally to increasing N-application. The effect of irrigation at the lowest N-rates was limited. The non-irrigated treatments with the highest N-rates had a grain/seed yield of 3.2, 2.3 and 0.7 t ha−1 and nitrate leaching rates of 64, 72 and 127 kg N ha−1 compared to a grain/seed yield of 5.3, 5.0 and 2.6 kg N ha−1 and nitrate leaching rates of 61, 42 and 85 kg N ha−1 (for spring barley, spring barley and winter oilseed rape, respectively). These results show that synchronised management of both irrigation and N-application are essential for reducing the risk of nitrate leaching and to promote efficient crop N-uptake in periods of droughts.</p

Atorvastatin improves plaque stability in ApoE-knockout mice by regulating chemokines and chemokine receptors.

It is well documented that statins protect atherosclerotic patients from inflammatory changes and plaque instability in coronary arteries. However, the underlying mechanisms are not fully understood. Using a previously established mouse model for vulnerable atherosclerotic plaque, we investigated the effect of atorvastatin (10 mg/kg/day) on plaque morphology. Atorvastatin did not lower plasma total cholesterol levels or affect plaque progression at this dosage; however, vulnerable plaque numbers were significantly reduced in the atorvastatin-treated group compared to control. Detailed examinations revealed that atorvastatin significantly decreased macrophage infiltration and subendothelial lipid deposition, reduced intimal collagen content, and elevated collagenase activity and expression of matrix metalloproteinases (MMPs). Because vascular inflammation is largely driven by changes in monocyte/macrophage numbers in the vessel wall, we speculated that the anti-inflammatory effect of atorvastatin may partially result from decreased monocyte recruitment to the endothelium. Further experiments showed that atorvastatin downregulated expression of the chemokines monocyte chemoattractant protein (MCP)-1, chemokine (C-X3-C motif) ligand 1 (CX3CL1) and their receptors CCR2 and, CX3CR1, which are mainly responsible for monocyte recruitment. In addition, levels of the plasma inflammatory markers C-reactive protein (CRP) and tumor necrosis factor (TNF)-α were also significantly decrease in atorvastatin-treated mice. Collectively, our results demonstrate that atorvastatin can improve plaque stability in mice independent of plasma cholesterol levels. Given the profound inhibition of macrophage infiltration into atherosclerotic plaques, we propose that statins may partly exert protective effects by modulating levels of chemokines and their receptors. These findings elucidate yet another atheroprotective mechanism of statins

Lesion features.

<p>* <i>p</i><0.05 <i>vs</i> group control.</p

Effect of atorvastatin (10 mg/kg/d) on atherosclerotic plaque morphology in ApoE-/- mice.

<p>(A) Representative images of H&E staining (scale bar = 100 µm) and intimal surface/media ratio quantification in the control and atorvastatin-treated groups (<i>p</i>>0.05, n = 10). (B) Representative images of immunostaining for α-SMC actin (scale bar  = 100 µm) and quantification (<i>p</i>>0.05, n = 6). (C) Representative immunostaining for macrophages (scale bar  = 100 µm) and quantification (*<i>p</i><0.05, n = 6). (D) Representative images of Oil Red O staining (scale bar  = 100 µm) and quantification (*<i>p</i><0.05, n = 6). (E) Representative images of Sirius red staining (scale bar  = 100 µm) and quantification (*<i>p</i><0.05, n = 6). Values are the mean ± SEM.</p

Effect of atorvastatin (10 mg/kg/d ) on collagenase activity and MMP-8 and MMP-13 expression in the neointima.

<p>(A) Representative images of in situ collagenase activity (scale bar  = 100 µm) and quantification in the control and atorvastatin-treated groups (*<i>p</i><0.05, n = 6). (B) Representative images of MMP-8 immunohistochemical labeling (scale bar  = 100 µm) and quantification in the control and atorvastatin-treated groups (*<i>p</i><0.05, n = 6). (C) Representative images of MMP-13 immunohistochemical staining (scale bar  = 100 µm) and quantification in the control and atorvastatin-treated groups (*<i>p</i><0.05, n = 6). Values are the mean ± SEM.</p

Effect of atorvastatin (10 mg/kg/d)on expression levels of intimal chemokines and their receptors e on peripheral blood monocytes in ApoE-/- mice.

<p>(A) Representative images of immunostaining for MCP-1 and CX3CL1 (scale bar  = 100 µm) and quantification in the control and atorvastatin-treated groups (*<i>p</i><0.05, n = 6). (B) Representative FACS analysis for monocytes with double-immunofluorescent labeling for CCR2 and CX3CR1. Data represent the mean ± SEM of the percentage of marker-positive cells from six experiments. *<i>p</i><0.05 compared with control.</p

Effect of atorvastatin (10 mg/kg/d ) on plasma inflammatory markers TNF-α and CRP in ApoE-/- mice.

<p>Blood was collected 8 weeks after isosmotic saline or atorvastatin administration. Data represent the mean ± SEM of six ELISA experiments. *p<0.05 compared with control.</p