天府黑兔新品系与新西兰兔生长发育规律及饲料转率的比较研究

随机选择天府黑兔和新西兰兔各60只作为试验动物,对两个品种的家兔早期生长性能和饲料转化率进行比较研究。结果表明:天府黑兔和新西兰兔在30～75日龄阶段,其生长速度呈上升趋势,75日龄后生长速度呈下降趋势;天府黑兔生长强度比新西兰兔大,30～90日龄平均日增重天府黑兔35 5g,新西兰兔27 5g,差异极显著(P<0 01);饲料报酬和成活率天府黑兔高于新西兰兔,但差异不显著(P>0 05)。     

农用稀土对农作物光合、呼吸强度影响的研究

本文通过田间、盆栽试验研究和分析了水稻、小麦、玉米等农作物喷施农用稀土后,植物叶片内叶绿素的含量,光合叶面积的大小,叶片的光合强度、呼吸强度的强弱。结果表明,农作物在营养生长阶段和生殖生长阶段。喷施稀土后,其叶片内叶绿素的含量大大提审尤其是叶绿素a增加特别明显,叶片的面积也增大,同时增强了叶片的光合作用和呼吸作用。     

兴津温州、脐橙果实发育研究初报 Ⅱ、果实成熟过程中的生理生化变化

兴津温州和华盛顿脐橙单果的呼吸强度从幼果至膨大期是急剧上升,而单位重量的呼吸强度则是幼果期最高,以后迅速下降。游离酸总量在果实膨大前期达最大值。果汁中可溶性固形物与总糖含量变化动态一致,到成熟前仍在持续上升。结果表明,在低温地区提高果实品质的途径,以增加果汁含糖量较降酸更为有效。     

Regional vegetation management standards for commercial Eucalyptus plantations in South Africa

During the 1990s a number of trials were implemented in the summer-rainfall region of South Africa to determine both the short- and long-term impacts of competing vegetation on eucalypt growth. Trial sites were selected across different physiographic regions such that a range of altitudinal, climatic and environmental gradients were represented. Although the understanding gained from these trials allowed for the development of vegetation management standards, their operational and economic viability needed to be tested on a commercial basis. Five eucalypt trials were thus initiated to test the applicability of these standards when utilised on a commercial scale. One of the trials was situated at a lower-altitude site (65 m above sea level [asl]), two at mid-altitude sites (878 and 1 262 m asl), and two at higher-altitude sites (1 469 and 1 590 m asl). Several vegetation management treatments developed to suit the predicted vegetation load at each site were implemented and varied according to either weeding intensity (high, moderate and low), or the area around the tree that was kept free of vegetation (no vegetation control, a row weeding and complete vegetation control). Following tree crown closure at each trial, tree growth was linked to the level of vegetation management in each treatment and its associated total cost up to canopy closure, allowing for the development of different cost-benefit comparisons. The intensity of vegetation management required to produce significant growth benefits decreased with increasing altitude, as did the area that needed to be kept free from competing vegetation. In contrast to the two higher-altitude sites, where tree growth did not benefit from vegetation management, a significant increase in tree growth occurred for the high- and moderate-intensity vegetation management operations at the three mid- and lower-altitude sites. Besides demonstrating the commercial applicability of research results, this series of trials has shown that site-dependent vegetation management is viable on a commercial scale and will allow the South African forest industry to adjust their weed control budgets on a regional basis (linked to altitude).     

The effect of defoliation on the persistence of elionurus muticus (spreng.) kunth in the highland sourveld of natal

A small plot trial with different heights of defoliation of unpalatable Elionurus muticus and other grass species was conducted over a six year period in the drier phase of the Highland Sourveld of Natal. Results indicate that moderate defoliation of the “palatable” species and little or no utilization of the E. muticus will cause the plant to decrease in size. Heavy, selective defoliation of the “palatable” species will result in an increase or thickening up of the E. muticus in the sward. No utilization of both components resulted in a marked decrease in E. muticus tuft size and heavy, uniform utilization of all herbage had little effect on the size of the E. muticus tuft.     

月季组培快繁技术研究

通过对５个切花月季品种组培快繁技术的研究,探讨了品种、植物生长调节剂、温度和光照强度等对外植体腋芽萌发、嫩茎增殖和生根的影响。茎段腋芽诱导适宜的条件是：ＭＳ＋ＢＡ３０ｍｇ／Ｌ＋ＮＡＡ０１５ｍｇ／Ｌ,温度２６℃左右。在ＭＳ＋ＢＡ３０ｍｇ／Ｌ＋ＩＡＡ０１５ｍｇ／Ｌ培养基上,嫩茎增殖达４倍以上。３０００ｌｕｘ左右的自然散射光对增殖阶段形成健壮嫩芽有利。小苗移植到沙子与椰糠混合的基质上,成活率达８０％以上。