Effect of soil acidification on the growth and nitrogen use efficiency of maize in Ultisols

Purpose

To examine the effect of soil acidification on growth and nitrogen (N) uptake by maize in Ultisols.

Materials and methods

A clay Ultisol derived from Quaternary red earth and a sandy Ultisol derived from tertiary red sandstone were used in this study. A pot experiment was conducted with maize growing in the two Ultisols acidified to different pH values. Urea with ¹⁵N abundance of 10.11% was used to investigate the distribution of N fertilizer between soil and plant. Total N content and ¹⁵N abundance in plant and soil samples were determined by elemental analysis-isotope mass spectrometry.

Results and discussion

Critical soil pHs of 4.8 and 5.0 were observed for maize growing in the clay and sandy Ultisols, respectively. Below the critical soil pH, increasing soil pH significantly increased maize height and the yield of maize shoots and roots (both P < 0.05), but changes in soil pH showed no significant effect on maize growth above the critical soil pH in both Ultisols. Maize growing in the sandy Ultisol was more sensitive to changes in soil pH than in the clay Ultisol. Increase in the pH in both Ultisols also increased N accumulation in maize, the N derived from fertilizer in maize, physiological N use efficiency, and N use efficiency (NUE) by maize. Changes in soil pH had a greater effect on these parameters below the critical soil pH, compared to above. The change in soil pH had a greater effect on N accumulation in maize, the N derived from fertilizer in maize, and NUE in the sandy Ultisol than in the clay Ultisol. The NUE increased by 24.4% at pH 6.0, compared with pH 4.0 in the clay Ultisol, while the NUE at pH 5.0 was 4.8 times that at pH 4.0 in the sandy Ultisol. The increase in soil pH increased the ratio of N accumulation in maize/soil residue N and decreased the potential loss of fertilizer N from both Ultisols.

Conclusions

Soil acidification inhibited maize growth, reduced N uptake by maize, and thus, decreased NUE. To maintain soil pH of acidic soils above the critical values for crops is of practical importance for sustainable food production in acidic soils.

     

Expression and functional characterization of glutamine synthetase from giant freshwater prawn (Macrobrachium rosenbergii) under osmotic stress

The freshwater prawn, Macrobrachium rosenbergii naturally lives in the freshwater, though it migrates to the brackish water environment during spawning that claimed to be resistant on a broad range of saline fluxes. However, little is known about the osmoregulatory patterns and the effect of an enzyme glutamine synthetase (GS) in M. rosenbergii under stress. Here, we described the identification and functional characterization of GS from M. rosenbergii (Mr‐GS) at molecular and protein levels. The identified Mr‐GS was comprised of 361 amino acids that phylogenetically shared the highest identity with other crustaceans and predicted to contain Gln‐synt_C and Gln‐synt_N domains at the respective terminal regions. Tissue distribution analysis in M. rosenbergii revealed that the Mr‐GS was highly expressed in muscle, and commonly existed in other examined tissues in the following order gills > heart > stomach > brain > haemolymph. Whereas, the mRNA of Mr‐GS was significantly up‐regulated in the muscle and gill tissues following challenges with either hyper (0 → 13‰), or hypo (13 → 0‰) osmotic stress at 3, 6 and 12 hr. Furthermore, the level of Glutamine concentration was positively correlated with the GS mRNA and protein expression patterns in hyper‐osmotic stress, whereas in hypo‐osmotic stress a slight decrease in the gills and maintained a level in the muscle tissues at 3, 6 and 12 hr post‐treatments. Our findings suggest that Mr‐GS potentially exhibited the osmoregulation responses in the gill and muscle tissues of M. rosenbergii throughout the time of osmotic stress, which will benefit for future study on osmoregulation.     

小麦TaCYP78A5基因的克隆及生物信息学分析

细胞色素P450(Cytochromes P450)蛋白家族含有硫羟基和血红素结构域,参与多种生物合成,CYP78A家族成员对籽粒大小形成有重要的功能。利用同源克隆的方法,分别从小麦大粒品系‘P271’和小粒材料‘中国春’中扩增到位于2AS、2BS、2DS上的TaCYP78A5-2A、TaCYP78A5-2B和TaCYP78A5-2D基因,编码534、544、549个氨基酸。通过分析发现在‘P271’和‘中国春’克隆到的TaCYP78A5序列一致,说明TaCYP78A5基因在这2个粒型的小麦中是保守的。CYP78A家族在水稻和拟南芥中具有非自主性细胞表达模式,结合对CYP78A家族的生物进化关系研究发现,CYP78A家族的各个基因在单子叶植物中是保守的。‘P271’和‘中国春’籽粒大小的差异,可能是TaCYP78A5基因在‘P271’中的基因表达量高于‘中国春’,引起种子发育过程中内表皮细胞的增殖,从而促进种子表皮增大,使得‘P271’种子大小和质量增加。     

京津冀地区植被NDVI动态变化及其与气候因子的关系

[目的] 探究气候变化对植被覆盖变化的驱动机制，可为揭示区域乃至全球植被覆盖动态变化及其与气候变化之间的响应机制提供依据。[方法] 以MODIS NDVI，SRTM DEM，降水和气温为数据源，运用Theil-Sen Median趋势分析法、Mann-Kendall显著性检验法、R/S分析法和Pearson相关分析法等数学分析方法，结合ANUSPLIN气象插值模型，研究2001—2019年京津冀地区植被NDVI时空演变特征及预测未来变化趋势，并探究植被NDVI与降水和气温最大相关关系及时滞效应。[结果] ①2001—2019年京津冀地区植被NDVI整体呈波动上升趋势，上升速率为0.002 2/a，且未来植被NDVI呈改善趋势的面积略小于呈退化趋势的面积；②降水和气温对京津冀地区植被生长以正向促进作用为主，且降水对植被生长的作用强度高于气温；③植被NDVI对降水变化的滞后期略长于气温，京津冀地区植被生长受前3月的降水和前1月的气温影响最大。[结论] 在林业生态工程实施背景下，2001—2019年京津冀地区植被覆盖整体呈改善态势，尤以西北部为著；植被NDVI与降水和气温相关关系呈现出明显的地域差异，且植被生长相对降水和气温变化存在一定的滞后效应。     

夏季高温环境下苦瓜种质资源农艺性状的综合评价

[目的]调查统计31份苦瓜种质资源在夏季高温环境下的农艺性状表现并进行耐热性分析评价,旨在建立田间苦瓜种质资源耐热性分析评价的方法和体系及筛选鉴定指标和优良耐热的苦瓜种质资源.[方法]连续两年在福建夏季高温环境下对31份苦瓜种质资源进行大田栽培比较试验,通过调查统计苦瓜的22个主要农艺性状指标,运用相关性分析、主成分分析和逐步回归分析对供试苦瓜种质资源进行综合分析评价.[结果]在高温环境下不同苦瓜供试材料产量差异较大,变异系数为35.48%,第一雌花节位、瓜长、瓜形和瓜瘤形状等果实性状变异系数在9.05%~41.27%,表现出丰富多样性,有利于耐热苦瓜种质资源的筛选.苦瓜产量与单瓜重、叶长呈极显著正相关(P<0.01,下同);单瓜重与瓜肉厚、瓜宽呈极显著正相关;第一雌花节位与植株分枝性呈显著正相关(P<0.05,下同),与主蔓节长呈显著负相关,各农艺性状指标之间反映的存在信息重叠,需要综合分析评价苦瓜种质资源的耐热性.主成分分析将22个农艺性状指标归纳为7个独立的综合指标(累计贡献率达76.654%),前5个主成分可概括为产量因子、瓜形因子、瓜瘤因子、早熟性因子和叶形因子,第六和第七主成分载荷最高的性状指标为种子性状,可概括为种子因子.主成分综合评价和聚类分析表明,表现优于CK的有7份苦瓜种质资源,具有植株分枝性强、主蔓粗壮、叶片大、单瓜重、瓜肉厚等特性.进一步利用逐步回归分析法建立了苦瓜种质资源耐热性评价数学模型F=-5.802+0.004X14+0.113X7+0.169X18+0.095X1+0.039X4+0.025X3+0.059X5+0.073X10-0.115X20+0.103X21+0.045X15,筛选出单瓜重、叶柄长、瓜瘤密度、植株分枝性、叶长、主蔓直径、叶宽、瓜色、种子颜色、种子花纹和瓜肉厚等11个耐热性鉴定指标.[结论]供试的K9、K10、K11、K20、K26、K28和K29等7份苦瓜材料可作为优异的耐热种质资源进行耐热苦瓜品种的选育.建立的数学模型和筛选出的11个鉴定指标可用于田间苦瓜种质资源耐热性的快速鉴定筛选,提高耐热育种效率.     

干制羊肉基因组DNA不同提取方法的比较

为了研究干制加工羊肉基因组DNA的最佳提取方法,本试验采用传统酚-氯仿法、磁珠法、改良CTAB法、离心柱法分别提取干制处理后的羊肉基因组DNA,并对4种方法提取的羊肉基因组DNA浓度、纯度、完整性以及提取所需时间、PCR扩增效果等进行比较。结果表明,采用磁珠法提取DNA的效果更好,DNA浓度为118.87 ng·μL^-1,A₂₆₀/A₂₈₀值为1.89,而且此方法具有提取时间短、效率高、污染小等特点。本研究结果为干制加工羊肉基因组DNA的大批量提取和检测提供了参考依据。     

低温贮藏对猕猴桃果实成熟软化相关基因表达影响

为探究低温对果实采后成熟软化与淀粉降解的影响,以红阳猕猴桃果实为试验材料,研究在低温贮藏期间,猕猴桃果实硬度,可溶性固形物、乙烯、淀粉含量以及淀粉酶相关基因的变化。结果表明,低温贮藏能显著抑制猕猴桃果实采后成熟软化,延缓果实淀粉的降解和可溶性固形物含量的增加,维持贮藏期间果实较高的硬度。低温贮藏抑制乙烯合成关键基因AcACO1和AcACS1的表达,抑制乙烯合成。同时,低温贮藏显著抑制淀粉降解相关基因AcAMY1、AcBAM1/3、AcISA3、AcLDA1和AcDPE1的表达。在低温贮藏后期,淀粉酶相关基因AcAMY1、AcBAM1/3、AcLDA1和AcDPE1的表达与乙烯释放速率有关。综上,低温贮藏延缓猕猴桃采后成熟软化进程与淀粉降解密切相关,可能主要通过抑制乙烯合成,从而影响贮藏后期淀粉降解速率,最终延缓果实软化进程。本研究结果为猕猴桃采后低温贮藏提供了理论依据。     

政策认知、执行力度与资源化利用满意度——基于河北省380家生猪养殖主体调研数据(上)

参与主体对于政策的评价是衡量政策实施效果的重要指标，探明政策参与主体满意度影响因素有助于了解主体自身需求，从而提高政策实施水平。文章基于对河北省380家生猪养殖主体调研数据，运用多元有序Logistic回归方法，分析生猪养殖主体自身政策认知以及相关政策执行力度对畜禽养殖主体废弃物资源化利用满意度的影响。结果表明：养殖主体资源化利用政策了解程度能够显著提升其资源化利用政策满意度；仅考虑养殖主体政策参与力度，随着参与力度增加，满意度亦会显著提升。但综合考虑其他因素，参与力度对于满意度提升效果则不再显著；养殖主体感知政策执行力度增加不利于政策满意度提升。此外，生猪养殖主体废弃物资源化利用政策了解程度增加，可以显著提升其报告资源化利用政策“满意”可能性。而单纯提高资源化利用政策执行力度并不能显著提高养殖主体资源化利用政策满意度。因此，要提高养殖主体政策满意度，应多渠道提升宣传力度，鼓励养殖主体积极参与，提高其参与意识，不断改善现有政策执行方式。     

Effects of ferulic acid on growth performance,immunity and antioxidant status in genetically improved farmed tilapia (Oreochromis niloticus) fed oxidized fish oil

A study was conducted to characterize the effects of dietary oxidized fish oil on the growth performance, immunity and antioxidant status of genetically improved farmed tilapia (Oreochromis niloticus) and to determine the role of ferulic acid on the oxidative damage induced by the oxidized fish oil. The tilapia (13.73 ± 0.31 g) were fed four experimental diets containing untreated (peroxide value, POV: 2.2 meq/kg) and highly oxidized (POV: 120.6 meq/kg) fish oil either with or without ferulic acid (0 or 400 mg/kg) supplementation for 12 weeks. From the results, the oxidized fish oil treatments increased antioxidant enzyme activities and MDA values but decreased the weight gain and the immunological parameters in tilapia. Meanwhile, the serum biochemical indices were significantly affected by the oxidized fish oil. Besides, the addition of ferulic acid partially counteracted the free radical‐induced damage and improved the health status of tilapia. In conclusion, the oxidized fish oil may induce oxidative stress, destroy liver, dysregulate lipid metabolism as well as reduce non‐specific immunity, and eventually result in growth inhibition of tilapia. The ferulic acid supplementation partially offset the negative effects of the oxidized fish oil on tilapia.     

池塘循环流水养殖模式配套草鱼鱼种养殖试验

为完善池塘循环流水养殖模式,满足大规格鱼种的需求,选择草鱼为研究对象,开展了配套草鱼鱼种的池塘养殖试验。试验分设7000和10000尾/亩(15亩=1 hm^2,下同)两个放养密度,每个密度设3个平行组。经过190多天的养殖,高、低密度试验组水质变化趋势一致。低密度组鱼种平均体质量为239.67g/尾,成活率75.48%,净产量18 856 kg。以200 g/尾的规格挑选,共选留59 300尾,选留率74.83%;高密度组鱼种平均体质量为179.33 g/尾,成活率93.97%,净产量23 471 kg。以200 g/尾的规格挑选,共选留55260尾,选留率42.00%。结果表明,虽然高密度组平均成活率和净产量均高于低密度组,但低密度组的平均规格和选留率均远高于高密度组,最后的选留量也高于高密度组,因此,7 000尾/亩的放养密度更加适合于池塘循环流水养殖模式配套草鱼鱼种养殖。