Performance and serum parameters of calves (Bos taurus) subject to milk restriction associated with supplementation with 2-hydroxy-4-(methylthio)butanoic acid

Our aim with this study was to evaluate the consumption, performance, quantitative characteristics of carcasses, biochemical profile, plasma levels of ghrelin and leptin, expression of the receptor for ghrelin (GHS-R1a) in the hypothalamus and duodenum, and the number of goblet cells in the duodenum of calves subjected to milk volume restriction and supplemented with 2-hydroxy-4-(methylthio)butanoic acid (HMTBa). We used 21 Holstein mixed-breed calves, aged between 3 and 15 d with an average weight of 36.8 kg, and housed in pens with troughs for hay, concentrate, and water. The study included two consecutive experimental periods (first period [P1] and second period [P2]) of 21 d each, with 7 d of adaptation to the diet and facilities. The calves were distributed in a completely randomized design in three treatments with seven repetitions. 1) Control: 6 liters of milk/d during P1 and 6 liters of milk/day during P2; 2) RES (milk restriction): 3 liters of milk/day during P1 and 6 liters of milk/day during P2; and 3) RES + HMTBa: 3 liters of milk/day during P1 and 6 liters of milk/day during P2 + 3.3 g of HMTBa/day in both periods. HMTBa was supplied in milk, and the amount of concentrated ration and hay provided and leftovers were recorded daily to estimate dry matter (DM) and crude protein consumption. Mean daily weight gain (DWG), final weight (FW), and feed conversion (FC) were obtained at the beginning and at the end of each 21-d period. Plasma concentrations of ghrelin and leptin, triglycerides, total protein, urea, lactate, creatinine, alkaline phosphatase, and cholesterol were measured for P1 and P2 at the end of each 21-d period. At the end of P2, animals were slaughtered; sections of the duodenum were collected to evaluate the expression of GHS-R1a and quantity of goblet cells; hypothalamus was used to evaluate the expression of GHS-R1a; rumen was used to evaluate the thickness of epithelium and keratin and the density, height, and width of ruminal papillae. In P1, total DM consumption, FW, DWG, glucose, and triglycerides were lower in the RES and RES + HMTBa groups (P < 0.001). In P2, there was an improvement in the FC of the RES + HMTBa group (compared with Control and RES groups) and a lower urea concentration in the RES group (compared with Control and RES + HMTBa groups) (P < 0.001). No differences were observed among groups regarding hormonal concentrations, histological parameters, and GHS-R1a expression in the duodenum and hypothalamus. Therefore, milk restriction combined with HMTBa supplementation promoted greater compensatory gain by a mechanism independent of changes in GHS-R1a expression and hormone levels of ghrelin and leptin.     

旱地高产小麦光合速率与产量变化的研究

在旱地大田条件下对鲁麦 2 1与D2 7两品种生育后期旗叶与群体光合速率、籽粒灌浆速率及产量变化进行了研究 ,认为旱地小麦要获得高产必须保持开花后高的旗叶与群体光合速率 ,以有利于籽粒灌浆速率维持 ,形成高产     

施肥比例及施肥量对玉米吸肥的影响及增产机理

盆栽试验表明,无论单施氮还是单施磷,均可提高玉米植株的氮素吸收量,但植株氮含量仍以最适施肥比例条件下的最大施肥量为最高,此时玉米叶片的叶绿素含量和光合强度也达到最大值,说明合理的施肥比例和施肥量是影响玉米叶片叶绿素含量和光合强度高低的重要因素。     

Effects of Stem-Injected Sucrose on Photosynthesis and Productivity of Water Stressed Corn Plants

Water stress during silking or early kernel development decreases the number of kernels set by corn (Zea mays L.) plants. Previous work has suggested that lack of assimilate supply due to water stress at silking was a major factor in the resulting reproductive failure. A greenhouse experiment was conducted to test the hypothesis that sucrose supplementation of water stressed corn plants can prevent decreased kernel set. Sucrose was injected into corn stems at three concentrations [0 (distilled water), 150 and 300 g L^?1] for 30 days starting at silking. Water availability was controlled by either maintaining a water table at 50 cm from the soil surface (well watered) or by withholding water starting one week before silking (water stress) until the fifth day after silking. The photosynthesis rate of water stressed plants was 25% that of well-water plants on the first day of silking. On average, the daily injection rate for distilled water was 1 mL higher than that of the sucrose treatments over a 30 day injection period. No difference in daily uptake rate was observed between the 150 and 300 g sucrose L^?1 treatments. Over water availability treatments approximately 17 g sucrose were injected into corn plants during the 30 day injection period. Corn plants receiving sufficient water supply produced bigger ears, with more seeds and greater 100-seed weight values, leading to higher total plant dry matter accumulation than water stressed plants. Injection of 300 g sucrose L^?1 increased the weight of the injected internodes by 28%, compared with distilled water injection. The highest grain yield was for the plants injected with 150 g sucrose L^?1, but only under sufficient water supply. The plants injected with 300 g sucrose L^?1 produced the least grain regardless of moisture availability. Thus, the exogenous sucrose supplementation influenced kernel set only under conditions of sufficient soil water supply. These results indicate that plant reproductive development after silking was limited more by water availability than assimilate supply, suggesting that some overall plant response to water stress, perhaps mediated by hormonal signalling, was more important than carbohydrate supply. These results indicated that plant desiccation occurred during floral development or pollination; irreversible loss of florets on unsuccessful pollination could result, thus, grain yield would be limited more by sink size than by availability of photosynthate.     

氮肥运筹对冬小麦光合特性和产量的影响

本试验以济麦22和鲁麦21为材料,研究了氮肥运筹对小麦光合特性,群体透光率和产量及其构成因素的影响。结果表明,在本试验的施氮量范围内,小麦叶面积指数、旗叶光合速率随施氮量增加而增加,而群体透光率、气孔导度及胞间CO2浓度则随施氮量的增加而降低;追氮时期后移有利于减缓后期群体叶面积的下降速度,但对气孔导度、胞间CO2浓度及光合速率等的影响较小。两个品种的籽粒产量均随施氮量的增加而增加。施氮量为225kg/hm2的3个处理中,拔节期追氮处理的产量高于其它两个追氮处理。在本试验条件下,获得高产的适宜施氮量为300kg/hm2,高产主要是通过较多的单位面积穗数和穗粒数,且追氮时期后移对籽粒产量所带来的影响较小。     

油菜光合作用及CAT对UV-B与AR胁迫的响应(Ⅰ)

采用水培试验方法研究了紫外辐射(UV-B,280～320nm)与酸雨(AR)单一和复合胁迫对油菜幼苗保护酶(CAT)及光合作用的影响。结果表明,单一胁迫与复合胁迫对油菜幼苗CAT活性及光合作用有不同程度的作用效果。在单一UV-B辐射(0.45W·m-2),单一酸雨(pH3.5)胁迫及复合胁迫下,质膜透性、MDA含量及CAT活性的增幅为8%、18.1%、26.0%,11.5%、21.6%、66.7%和28.8%、85.0%、113.8%;叶绿素含量、净光合速率、蒸腾速率、水分利用效率及气孔导度降幅为16.5%、48.6%、57.2%,28.6%、42.9%、78.6%,3.9%、12.4%、14.8%,27.8%、31.0%、74.5%和35.6%、38.2%、44.7%;而胞间CO2浓度的增幅为9.3%、10.6%、26.4%。结果显示,复合胁迫的抑制效应强于单一胁迫,即UV-B+AR>UV-B>AR,且对不同指标的影响不尽一致。     

连栋塑料大棚内温湿度及番茄叶片净光合速率的垂直和水平分布特征

为探索连栋塑料大棚内气候因子的变化特征，对温室内垂直方向和水平方向的气温和相对湿度进行了连续的观测，结果表明，不同天气条件下温室内平均气温和平均相对湿度具有明显的变化特征。番茄叶片净光合速率的梯度分布特征是上部最大，中下部则迅速下降。     

中国北方主要针叶造林树种苗木质量的研究（Ⅴ）──苗木形态与苗木生理的关系

对油松、侧柏苗木形态与生理之间关系的研究表明：在正常生长情况下，苗木形态特征是苗木生理状况的外在表现。同一批苗木内，苗木形体越大，则针叶内Ｎ，Ｐ，Ｋ浓度越高，总含量越大，并且叶绿素含量和净光和速率也越高，因此苗木形态在一定程度上反映了苗木质量。     

不同光温背景下镧对辣根生态生理学效应(Ⅰ):对辣根光合作用影响

采用土培法培养试验,研究在不同光照（1.5、3.0、5.0、8.0、12.0、20.0klx）和温度（10、15、20、25、30、40℃）条件下稀土镧（La）对辣根光合作用的影响。结果表明,辣根适宜生长温度为15～25℃,适宜浓度稀土La（Ⅲ）能明显提高辣根的叶绿素（Chl）含量、净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）,其中以20mg·L^-1效果最佳;高、低温下喷施La（Ⅲ）不利于辣根的光合。在较低光照幅度下,La（Ⅲ）仍能有效促进辣根光合作用,呈“低促高抑”现象。且在较低的光照幅度范围内,对较低光照幅度下的促进作用优于较高光照幅度。