黄河三角洲地区鲈鱼越冬技术研究

根据海水盐度不同，其结冰点就不同的原理，进行了自然环境下鲈鱼大面积越冬试验，发现盐度越低，鲈鱼越冬成活率越高，最好将池水盐度控制在10以下，并指出越冬鱼种规格100－200g／尾为宜。     

Factors that limit maintenance of recombinant rumen bacterium in sheep rumen

Factors limiting the maintenance of recombinant ruminal bacterium in the rumen were evaluated in vitro , using batch culture prepared from rumen fluid of sheep. Butyrivibrio fibrisolvens expressing a foreign xylanase gene ( B. fibrisolvens NO4) was used as a tested recombinant that was selectable on an erythromycin-containing agar medium. The recombinant tended to reduce its level slowly in the rumen fluid of sheep on a high hay diet, while its initial decrease was more apparent in the rumen fluid of sheep on a high concentrate diet. Incubation with cell-free ruminal fluid revealed a significant decrease of inoculated recombinant, suggesting the presence of antibacterial factors limiting maintenance of the recombinant. In particular, during the first 12 h of incubation this inhibition was more notable in culture prepared from rumen fluid of sheep given the high concentrate diet. Autoclaving the cell-free rumen fluid inactivated the inhibition. Numbers of the recombinant for inoculation did not influence the final level of survived recombinant, that is, the initial depression was larger as more recombinant was inoculated. Subculturing with xylan before inoculation and/or direct addition of xylan to the batch culture did not improve survival of the recombinant. From these results it is suggested that the level of survived recombinant is limited to 10^2–4/mL of in vitro batch culture with restricted energy supply and that initial depression of the recombinant is mainly caused by the heat-sensitive antibacterial factors not associating with microbial cells in the rumen.     

Genetical studies of embryo survival and embryo breakdown in Pelargonium × hortorum Bailey

Summary The 6×6×4 analysis of variance of the mean percentage embryo survival for six variegated cultivars of Pelargonium × hortorum Bailey, with mutant plastids in their germ layers, and for their isogenic green (G) clones, shows highly significant differences between females (81 to 91 per cent) and between plastid crosses (83 to 91 per cent). Between cultivar differences are attributed largely to additive effects corresponding to additive gene action, and between plastid differences to a lower survival after crosses with white (W) males than with green males. The relationship between overall fertility (% fertilization × survival) and plastid crosses is a stepwise decline in the order G×G>G×W>W×G>W×W (28 to 19 per cent) in which the white embryos growing in a white mother are approximately 30 per cent less fertile than the green embryos in a green mother. The non-surviving embryos are classified into empty, undeveloped and dwarf embryos and submitted to a 6×4 analysis of variance after summing through males. The significant heterogeneity between females is attributed largely to a difference between one cultivar-with a high frequency of dwarf and a low frequency of undeveloped embryos-and the other five cultivars. The absence of a significant plastid effect upon any stage of embryo breakdown indicates that the depressive effect of white plastids is spread evenly throughout development.     

飞播造林苗木存活率影响因素分析

从气候、土壤、人畜活动、病虫害等方面综合分析了飞播造林存活率影响因素,并提出了相应对策。     

降水和气温因子与造林成活率关系的调查与分析

对东丰县大阳林场2006～2010年连续5 a的造林成活率进行调查,分析其与降水和气温两个因子的关系,结果表明：在造林树种、密度、立地条件和苗木质量基本相同的前提下,年平均温度是影响造林成活率的最关键因子,此外,3～5份的温度对成活率亦有显著影响,低温常导致造林成活率降低。降水量在满足苗木成活的基本要求后,其作用不甚明...     

香樟试管苗移植技术研究

运用正交试验的方法研究炼苗时间、不同遮阳网遮光率以及不同基质对香樟试管苗移植效果的影响,结果表明:炼苗时间7 d,遮阳网遮光率60%,基质为木屑∶泥炭土(1∶1)对于香樟试管苗移植效果最佳。     

水土保持行政处罚决定执行中存在的问题及对策

水土保持行政处罚决定执行中存在的问题及对策何建华（山西省水利厅水保监督处,太原市０３０００２）李茂华（山西省寿阳县水利水保局）水土保持监督管理部门是代表国家行使水土保持管理职权的行政机关,它对造成水土流失行为的个人或单位作出的行政处罚决定,采取的一定...     

龙须草栽植成活率的研究

采用育苗成分蔸移栽龙须草，共成活率一般教低度于５０％，制约了这一优良保土经济草种的发展。对影响龙须单栽植成活率的研究表明：冬前整地来年移栽较边整地边移栽、在气温高的６～８月较早春或晚狄移栽、雨天移栽效晴天移我、免耕并深栽较翻耕浅植均可显著提高龙须草的成活率；在相同栽培条件下．就近育苗、随起随栽，尽可能缩短种苗放置时间是保证龙须草成话的关键，人工保墒措施也不失为提高龙须草成活率的有效手段。