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21.
水分胁迫对荔枝幼树根系与梢生长的影响 总被引:7,自引:0,他引:7
以盆栽沙培1年生荔枝空中压条苗为试材,研究了水分胁迫对荔枝幼树根系和梢生长的影响以及二者的相互关系。3个处理为:沙体积含水量为7.5%(严重缺水),15.0%(一般缺水),22.5%(充分供水)。结果表明:水分胁迫严重抑制荔枝幼树地上部分和各级侧根的生长,使地上部枝梢生长严重受阻,叶片数量、平均叶面积、叶片厚度均显著变小;根总干重、侧根长度、根表面积显著减少。水分胁迫下促进须根的生长,须根的长度、根表面积比水分充足时显著增加。水分胁迫时叶片淀粉含量下降,而根系积累更多的淀粉。比较不同处理的根梢比发现,干旱对根系生长的抑制作用比枝梢更显著。 相似文献
22.
中密度纤维板砂光机的改进及降耗 总被引:2,自引:0,他引:2
笔者分析了中密度纤维板砂光机消耗较高、质量较差的原因,提出了改进措施。实施结果表明,砂光机运行正常,砂光产量和质量同步提高,消耗和成本下降,污染减轻。 相似文献
23.
采用氮吸附法对4种生物质焦(稻壳、树叶、玉米秆、棉花秆)的孔隙结构进行测量,结果表明,不同种类焦样的比表面积和孔径分布有明显差别,树叶的比表面积最大,为242.21 m2·g-1,玉米秆的比表面积最小,为0.81 m2·g-1.850℃时,稻壳、树叶、玉米秆焦样的孔径分布曲线在微孔和中孔范围各有一个分布峰,而棉花秆焦样的孔径分布曲线只在中孔范围内出现一个分布峰.热解温度是影响孔隙结构的一个重要因素,在高温条件下,同步热解得到的焦样的比表面积较大,微孔较多.在本研究中,600℃、850℃的稻壳焦样和850℃的树叶焦样具有较大的比表面积,比较适合做吸附剂. 相似文献
24.
25.
猪肺炎支原体及其生物学研究进展 总被引:10,自引:0,他引:10
猪肺炎支原体是引起猪支气管肺炎的主要病原 ,严重危害着养猪事业的发展。虽然猪肺炎支原体的结构简单 ,但由于它对营养要求较高 ,故培养难度大 ,也是人们不能对其深入研究的一个主要原因。近年来利用克隆技术 ,对猪肺炎支原体从基因水平上进行了多种研究 ,已经取得了一些可喜成果。文章从它的生物学特性、荚膜结构、膜蛋白研究以及基因水平的研究等方面进行了综合性论述 ,并简明地指出了目前研究中存在的问题以及未来展望 相似文献
26.
J. W. Claussen 《Forest Ecology and Management》1996,80(1-3):245-255
Current practices in many nurseries involve the germination of tropical rainforest seedlings in shaded conditions and transferral, at a later date, to environments with greater light intensities. Determination of the ability of these seedlings to acclimate to increased light intensities will allow seedling stock to be processed with maximum efficiency within the nursery. The acclimation abilities of three species, Agyrodendron actinophyllum, Cardwellia sublimis, and Flindersia brayleyana, commonly found in north Queensland's rainforests were investigated in this study. These particular species are highly valued for their cabinet timber qualities and are being reared in nurseries for use in reforestation trials and programs in north Queensland. Seedlings were initially raised in greenhouse conditions under two layers of shade cloth (16% of full sunlight) and then transferred into full sunlight at three different ages (3 weeks, 10 weeks, 14 weeks). Upon transfer, organ ratios and the direction of dry matter distribution was determined for each species and age group. Approximately 3 months after the seedlings were transferred, the acclimation ability of each species and age group was then determined. Dry matter distribution was found to change with age, irrespective of light environment. Individuals within a species with larger root systems and thicker or more dense leaves had a greater acclimation ability than those with smaller root systems and thinner or less dense leaves. Furthermore, individuals within a species whose dry matter distribution upon transfer was directed towards developing a large root system, and a small photosynthetic area and mass, had a greater acclimation ability than those whose dry matter distribution was directed away from such morphologies. Awareness of these relationships allows a better understanding of seedling response to gap formation in natural forests, and also allows plant nursery operators to make a more informed decision about when to move seedlings to environments with a higher light intensity. 相似文献
27.
针对龟石灌区农业用水效率低下、浪费严重等问题,提出了节水措施,分析了节水改造的潜力与效益。灌区水资源优化配置与合理利用,提高灌溉水利用率和水分生产率,富余水量用于城市供水及发电,提高单位水量的价值不仅是必要的,而且是灌区发展的必由之路。 相似文献
28.
选用6只9周龄新西兰母兔,评定环境温度和饲粮营养浓度对生长期母兔代谢能利用率的影响。试验在密闭式的小动物呼吸测热柜中进行。分别对处于环境温度为20±2℃和30±2℃,采食两种不同营养浓度的试兔进行测试。饲粮营养水平实测值,分别为12.22kJ ME/g和13.49kJ ME/g;粗蛋白质(CP)分别为17.3%和21.6%;中性洗涤纤维(NDF)分别为23.7%和16.5%。结果表明:环境温度影响试兔的能量平衡,它与采食量间存在着显著的相关。20±2℃时,相关系数r=0.798;30±2℃时,相关系数r=0.875。在本试验设计范围内,饲粮营养浓度并不影响代谢能食入量(ME_I),热增耗(HP)和能量平衡(EB)。当环境温度为20±2℃和30±2℃时,表观代谢能转化率(NE/ME)分别为51%和71%;每天每兔每千克代谢体重代谢能维持需要分别为396 kJ和361 kJ。试验结果认为:环境温度影响营养物质消化率(P相似文献
29.
Root development of sugar beet plants on a sandy loess site with regard to nitrogen nutrition.
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm−3 .
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm−3 . Thus, the plants gain not only access to water reserves, but sometimes meet remarkable amounts of nitrate which under the relatively dry conditions of the region tends to accumulate in 60–120 cm depth and – when taken up by the beet plants in the late stage of growth – affects crop quality negatively. 相似文献
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm
30.