牧压和肥力对亚热带山地牧草净生产的影响

在亚热带山地湿润环境条件下,研究牧压和土壤肥力对人工草地净生产的影响.三年试验结果表明,绵羊在轮牧下,产草量和磷肥对全年及各月牧草净生产具有显著影响.禁牧时,夏季地上生物量积累到一定程度后,只有很少量的净生产.放牧时,产草量在1000 kg DM/hm2左右时,净生产最大,当产草量低于300 kg DM/hm2以下时,净生产量则降低.每年施一次P2O5 36～60 kg/hm2,可以显著增加牧草净生产,尤以春末夏初时施肥更为显著.最低产草量出现在不施肥处理.     

A BOOST TECHNIQUE FOR IRRADIATION OF MALIGNANT CANINE NASAL TUMORS

Eighteen dogs with malignant nasal cavity tumors were treated with radiation therapy, including a boost technique. Three 3:0 Gy boost doses were added to a treatment protocol consisting of sixteen 3.0 Gy daily fractions, bringing the total dose to 57 Gy. This boost technique was implemented without an associated increase in overall treatment time by giving the boost doses on a twice-a-day basis. Boost doses were given during the first half of the radiation therapy period. The treatment was completed as planned in 16 of the 18 dogs; two dogs received lower doses (51 and 54 Gy). Median survival was 177 days, poorer than in some other reported studies of nasal tumor irradiation. Acute effects were unacceptable, with 11 of the 18 dogs developing severe mucositis, desquamation, edema, swelling, and pruritus. The extensive nature of the acute reactions compromised assessment of the effect of the increased radiation dose on the tumor. Although there is justification for assessing more aggressive radiation protocols in canine nasal tumor patients, total doses approximating 60 Gy can not be given as described because of the inability of acutely responding normal tissues to compensate.     

^60Co—γ射线对玉米当代（Mo）染色体断裂规律的分析

~(60)Co-γ射线辐射玉米干种子对影响当代(Mo)染色体断裂的研究表明,断裂频率以1号和具随体的6号染色体最高,7、9和10号染色体很低,且基本不受辐射剂量大小的影响。染色体断裂数量与染色体长度无显著相关。断裂常发生在异染色质与常染色质的结合处.     

茭白主茎地上部养分积累和转运规律

以两个有代表性的茭白品种为试材,测定了植株主茎生育过程中地上各部位干、鲜质量的积累及叶片净光合速率的变化。结果表明在田间封行前,植株主茎叶和短缩茎的干、鲜质量持续缓慢增加;封行后至肉质茎快速膨大前,短缩茎的物质积累超过叶片和叶鞘;肉质茎快速膨大期间,干物质积累主要在其前期,同时短缩茎等其余部位干、鲜质量明显下降;之后肉质茎干、鲜质量增加趋缓,叶片、叶鞘质量仍持续下降,而短缩茎质量回升,进入新一轮物质积累期;主茎的总干物质量在封行后迅速提高,在肉质茎充分膨大后下降。功能叶片净光合速率在生育进程中总体呈持续缓慢下降的趋势,肉质茎快速膨大期间迅速大幅上升,紧接着又快速回落。     

樱桃不同节位叶片光合特性与解剖特征比较研究

以3个甜樱桃栽培品种佐藤锦、斯坦勒和那翁为试材,研究了新梢不同节位叶片光合速率(Pn)变化及叶绿素(Chl.)和比叶重(SLW)对其的影响。分析了不同品种叶片解剖结构与Pn的关系。结果表明:樱桃枝条不同叶位叶片的Pn呈单峰曲线变化,枝条中上部的叶片Pn较大,且有较高的稳定性,叶片发育和生理成熟度以及环境因素的影响是Pn出现单峰变化的重要因素;Chl.含量随着叶片的发育而增加,叶片成熟后,叶片Chl.含量与Pn之间不存在相关关系;不同叶位叶片SLW与Pn表现显著正相关;樱桃不同品种间叶片气孔密度、栅栏组织与海绵组织厚度比值与Pn存在极显著正相关。     

多花黑麦草品种比较试验

通过对现行生产中常用的4个多花黑麦草品种在昆明地区的物候期、株高、草产量、生长率、净同化率等指标的规定表明,在生长初期,特高的生产性能比其余3个品种都好,但生长一段时间后,邦德的生产性能明显超过特高(P<0.05),抗锈王略高于特高(P>0.05),旺饲的生产性能最差(P<0.05)。因此,邦德是一个在生产中值得推广应用的品种。     

营养液浓度及pH值对山葵生长及光合速率的影响

 探讨了0.5、1.0、1.5 倍日本园试营养液3 种浓度(以清水为对照) 和5.4、6.0、6.6、7.2 等4 种pH 值对山葵生长和光合速率的影响。结果表明, 在营养液1.0 倍和pH 6.0 条件下, 山葵平均根茎鲜质量为42.75 g , 且叶绿素含量和净光合速率显著高于其它处理。     

Preliminary study of plasma vascular endothelial growth factor (VEGF) during low- and high-dose radiation therapy of dogs with spontaneous tumors

High plasma vascular endothelial growth factor (VEGF) concentrations are associated with radiation resistance and poor prognosis. After an exposure to ionizing radiation in cell culture an early phase and a late phase of increased VEGF have been documented. The activation was dependent on the radiation dose. Therefore, the purpose of this study was to measure baseline plasma VEGF and changes in VEGF over the course of fractionated radiation therapy in dogs with spontaneous tumors. Dogs with tumors had a significantly higher pretreatment plasma VEGF than did dogs without tumors. Immediately after irradiation no increased plasma VEGF was observed. Over the course of radiation therapy there was an increased plasma VEGF in dogs treated with low doses per fraction/high total dose, whereas plasma VEGF remained stable in dogs irradiated with high doses per fraction/low total dose. The regulatory mechanisms are very complex, and therefore the value of plasma VEGF measurements as an indirect marker of angiogenesis induced by radiotherapy is limited.     

UV-absorbing compounds and susceptibility of weedy species to UV-B radiation

Stratospheric ozone (O₃) depletion has led to increased terrestrial ultraviolet‐B (UV‐B) radiation (290–320 nm). Leaves exposed to this radiation produce UV‐absorbing compounds in the epidermal cells, which protect plants from UV‐B damage. To determine the role of UV‐absorbing compounds in the UV‐B sensitivity of weeds (common chickweed (Stellaria media), downy brome (Bromus tectorum), green smartweed (Polygonum scabrum), redroot pigweed (Amaranthus retroflexus), spotted cat’s‐ear (Hypochoeris radicata), and stork’s‐bill (Erodium cicutarium)) seedlings were exposed to 0, 4 (field ambient), 7 (18% O₃ depletion) and 11 (37% O₃ depletion) kJ m^?2 d^?1 of biologically effective UV‐B radiation in a greenhouse. Ultraviolet‐absorbing compounds were extracted from the second true‐leaf (0.5 cm² samples) with methanol : distilled water : HCl (79 : 20 : 1) in an 85°C water bath for 15 min, and the absorbance of the extracts measured at 300 nm. The shoot dry biomass was recorded to determine the susceptibility to UV‐B radiation. Common chickweed was the most sensitive and green smartweed the least sensitive weed to UV‐B radiation. The latter accumulated more UV‐absorbing compounds and this accumulation occurred earlier compared with common chickweed. As UV‐B_BE radiation levels increased from 0 to 11 kJ m^?2 d^?1, the green smartweed shoot biomass did not decline. However, the biomass of all five susceptible species declined despite an increase in the UV‐absorbing compounds in response to increased UV‐B radiation. Therefore, formation of a ‘UV‐screen’ in these species is not sufficient to fully prevent UV‐B damage. When the concentration of UV‐absorbing compounds in the six species was plotted against their susceptibility to UV‐B radiation, no relationship was observed. Thus, while the accumulation of UV‐absorbing compounds may be a major factor in the protection of certain species against UV‐B radiation and may offer some degree of defence in other species, it does not explain UV‐B susceptibility differences in weedy species in general.     

狗牙根辐射诱变后代外部性状变异分析

对1997-2002年经过辐射诱变得到的狗牙根诱变后代的6个坪用性状指标的统计分析结果表明,1)不同的辐射诱变剂量处理的后代间坪用性状有显著差异,尤其在节间直径和密度上,6 800 rads处理的后代节间都比9 000 rads处理的后代粗,而密度是前者低于后者,2种剂量处理都可以显著降低草层高度;2)不同辐射诱变代数的后代间存在着差异,原始种源进行多代的辐射诱变,可以使得叶片显著变窄,草层高度显著降低,节间变细变长; 3)同一材料在相同辐射剂量诱变处理后匍匐茎不同节之间也存在显著的差异.