玉米磷酸烯醇式丙酮酸羧化酶基因的研究进展

高等植物按照CO₂不同的同化途径,分为C₃、C₄和CAM植物。由于C₄植物具有高光效基因,使其在高温、高光照、高氧分压条件下具有比C₃植物更高的光合作用效率。目前,很多学者致力于研究玉米中的高光效基因-磷酸烯醇式丙酮酸羧化酶基因（PEPC）,并试图将此基因转入到C₃植物中,使C₃植物的光合特性得到一定改善,进而使其产量提高。本文综述将C₄高光效基因转入到C₃植物后,C₃植物的生理生化变化和对其光合作用的影响,对向C₃植物中导入pepc基因能否提高其光合作用效率和产量的潜在可能性进行探讨。     

温度与土壤水分对玉米种子萌发及幼苗生长特性的影响

以沈单16、豫玉22为试验材料,研究不同温度、土壤水分对玉米种子萌发及幼苗生长特性的影响.结果表明,随温度与土壤水分的下降种子发芽势、发芽率均呈降低趋势.温度与土壤水分对幼苗生长各指标的影响不同,玉米芽鞘长、幼苗长、贮藏物质转运率和叶绿素含量均随温度与土壤含水量的降低而减小;过氧化物酶活性、脯氨酸含量呈先增加后降低的趋势.在环境温度低于15℃恒温条件下,玉米种子发芽率迅速降低,土壤含水量低于10％时种子不能正常萌发;在15℃及以下低温,土壤含水量低于10％时玉米幼苗生长受到抑制.持续性低温、干旱胁迫不利于玉米种子的正常萌发与幼苗的生长.     

秸秆还田与覆膜对土壤理化特性及玉米生长发育的影响

试验研究秸秆还田对不同覆膜时期的全膜双垄沟播玉米生长发育与土壤理化特性的影响。结果表明,经秸秆还田后全膜双垄沟播耕层土壤养分含量变化依次表现为整株还田>秸秆粉碎>免耕留茬,不同覆膜时间对土壤养分变化影响不明显;秸秆还田土壤容重明显降低但免耕留茬一膜两年用处理土壤容重增大。在玉米生育前期经秸秆还田后的土壤温度与水分均显著低于对照,其株高、茎粗与叶面积均小于对照;在玉米生育后期秸秆腐解后对土壤水分起到一个补偿效应。玉米产量表现为秋覆膜整株秸秆还田>顶凌覆膜整株秸秆还田>秋覆膜秸秆粉碎还田>顶凌覆膜秸秆粉碎还田>免耕留茬一膜两年用,秸秆还田后玉米产量较对照有增产趋势,而免耕留茬一膜两年用有减产倾向,但处理间差异不显著。     

DOES MEASUREMENT OF SMALL INTESTINAL DIAMETER INCREASE DIAGNOSTIC ACCURACY OF RADIOGRAPHY IN DOGS WITH SUSPECTED INTESTINAL OBSTRUCTION?

The ratio between maximal small intestinal (SI) diameter and the height of the body of the fifth lumbar vertebra (L5) in radiographs has been reported as a diagnostic test in dogs with suspected intestinal obstruction. In order to assess the effect of the SI/L5 ratio on the accuracy of radiographic diagnosis of intestinal obstruction, lateral abdominal radiographs of 37 dogs with small intestinal obstruction and 48 nonobstructed dogs were mixed and examined independently by six observers who were unaware of the final diagnosis and who represented a range of experience. Observers first examined radiographs subjectively and stated the likelihood of obstruction (definitely not, probably not, equivocal, probably, definitely). Observers subsequently reexamined the radiographs, determined the SI/L5 ratio, and again stated the likelihood of obstruction. The most frequent cause of obstruction was foreign body (29/37, 78%). Dogs with SI obstruction had a significantly larger median SI/L5 ratio than nonobstructed dogs (P = 0.0002). Using an SI/L5 ratio of 1.7 for diagnosis of intestinal obstruction, sensitivity and specificity were 66%. Use of the SI/L5 ratio was not associated with increased accuracy of diagnosis for any observer, regardless of experience, hence this test may have no diagnostic impact.     

4个核桃品种光合特性的日变化

采用LI 6400便携式光合测定仪,分析鲁光、扎343、强特勒、中林5号4个核桃（Juglans regia）品种光合特性的日变化,以期为核桃的优质高产和规范化生产提供理论依据。结果表明,4个不同的核桃品种净光合速率（Pn）日变化均呈现双峰曲线,且在14:00均出现显著的“午休”现象;强特勒、中林5号较鲁光和扎343更早地受到了光抑制。4个核桃品种Pn与光合有效辐射（PAR）均存在显著正相关,相关系数由大到小依次为扎343>强特勒>鲁光>中林5号。     

青藏高原几种高山植物的光合生理特性

以14种高寒草甸植物为材料,研究分析植物叶片的光合色素含量和叶绿素荧光参数,以探究高寒草甸植物适应青藏高原极端环境的光合生理机制。结果表明,黄花鸢尾(Iris pseudoacorus)、美丽风毛菊(Saussurea pulchra)、鹅绒委陵菜(Potentilla anserina)和天蓝苜蓿(Medicago lupulina)叶片的单位面积叶绿素含量分别比黄帚橐吾(Ligularia virgaurea)高284.83%、200.56%、171.35%和148.31%,叶片PSⅡ有效光化学量子产量分别高79.99%、73.94%、68.37%和63.90%,叶片PSⅡ实际光化学效率也具有相同的变化趋势;而黄花鸢尾、美丽风毛菊、兰石草(Lancea tibetica)和麻花艽(Gentiana straminea)叶片的单位叶面积类胡萝卜素含量分别比天蓝苜蓿高393.93%、348.48%、260.61%和233.33%,其叶片的非光化学猝灭也显著高于天蓝苜蓿;黄帚橐吾、珠芽蓼（Polygonum viviparnm）和柔软紫苑(Aster flaccidus)叶片的叶绿素a/b值高于2.91,能适应较强光照,而天蓝苜蓿叶片的叶绿素a/b值小于2.5,常生长于植被下层,说明植物能够通过调整光合色素含量和构成而合理有效地利用光能以适应特殊的环境条件。     

贵州省古银杏资源的分布及生长特征研究

2011年8月通过访谈、查阅文献资料与实地调查,对贵州省古银杏资源的分布及生长特征进行分析。结果表明,贵州省100～4000年生古银杏共有1969株,主要分布于遵义市和六盘水市;垂直分布海拔为300～1700m,集中分布800—1100m。其中75．96％为雌株,24．04％为雄株,雌雄比为3．16：1;树高最高为50．0m,最矮为2．0m;树龄最大为4000年,最小为100年;胸径最大为479cm,最小为26cm;其平均冠幅最大为40．0m,最小为1．0m。垂乳银杏有88株,复干银杏有35株,雌雄同株仅1株。     

Prediction of enteric methane production from dairy cows

Abstract

The main objective of this study was to elucidate the potential for prediction of enteric methane (CH₄) emissions from dairy cows by using predicted rumen plus hindgut digested (fermented nutrients) and total tract digested nutrients (by using NorFor) as input variables. Twenty-one experiments (78 dietary treatments) were collected. The data-set was used to develop prediction models and to test their and extant models ability to predict enteric CH₄ emissions. Models were compared based on mean squared prediction error and concordance correlation coefficient (CCC) analysis. Fermented nutrients did not predict enteric CH₄ emissions adequately (CCC < 0.420). Including total digested (td) nutrients in the model [CH₄ (MJ/d) = ?2.13 + 1.64 tdOM (kg/d) ?9.74 tdFat (kg/d) + 1.64 tdNDF (kg/d)] predicted enteric CH₄ emissions more precisely (CCC = 0.733), and showed an improvement in the prediction of enteric CH₄ emissions over the extant models tested.     

红安县花生土壤的特征及改良利用

红安县花生土壤多为片麻岩发育而成的黄棕壤,耕层浅薄,质地偏砂,剖面发育不完整,水、肥、气、热资源有限,土壤养分缺乏.应充分利用坡改梯、深翻改土、发展灌溉、增施有机肥、配方施肥、合理轮作、地膜覆盖等技术措施提高地力水平,达到花生增产增效的目的.     

四种樟属树种幼树的光合生理特性比较

采用Li-6400光合测定仪系统研究了樟属树种香樟、岩桂、天竺桂、猴樟的幼树在不同生长季节的田间光合生理特性.结果表明,4种樟属树种幼树在春季、夏季的净光合速率日变化都呈“双峰”型曲线变化,出现典型的“光合午休”现象,并且第一峰值高于第二峰值;而在秋季各树种幼树的净光合速率日变化则都呈“单峰”型曲线变化.4种树幼树的光合作用生理指标各不相同,但光适应能力均较强;其中,净光合速率高低排序为香樟、猴樟、天竺桂、岩桂,光饱和点高低排序为香樟、猴樟、天竺桂、岩桂,光补偿点高低排序为天竺桂、猴樟、岩桂、香樟,表观量子效率高低排序为香樟、猴樟、天竺桂、岩桂,CO2补偿点高低排序为猴樟、天竺桂、岩桂、香樟.多元逐步回归分析结果表明,影响净光合速率的关键环境因子随树种不同而变化,对香樟的净光合速率有显著影响的因子是光合有效辐射、气孔导度和胞间CO2浓度,对岩桂和天竺桂的净光合速率有显著影响的因子是气温、气孔导度和胞间CO2浓度,对猴樟的光合速率有显著影响的因子是光合有效辐射和气温.