Comparison of growth,survivorship, seed production and shedding of eight weed species in a wheat crop in Western Australia

Development of integrated weed management strategies is dependent on a thorough knowledge of the demography of individual species. The current research established eight winter or summer weed species in a winter annual wheat cropping system at Wongan Hills, Western Australia, and investigated emergence of the first cohort of each species, survivorship, plant size, seed production and seed shedding over three years (2016–2019). The winter weeds Bromus diandrus and Lolium rigidum emerged at the same time as the wheat crop, and the initial cohort of marked plants had 100% survival to seed production in each year. By comparison, other winter weed species like Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus and Polygonum aviculare frequently emerged later than the crop and had a lower percentage of plants surviving to seed production. However, individual S. oleraceus and P. aviculare plants had the greatest seed production compared to other species. All winter weeds had variable patterns of seed shedding between years, with the exception of L. rigidum. Summer weed species emerged at the same time, but plants in the initial cohort of each species did not always survive to produce seed. The early emergence and high survivorship of B. diandrus indicates high competitive ability, but shedding commenced at a similar time to L. rigidum and harvest weed seed control may be a viable control method for this species.     

浙江红花油茶高接换冠成活率影响因素研究

为研究浙江红花油茶高接换冠成活率影响因素,解决嫁接成活率低的问题,2013年6月从中国林业科学研究院亚热带林业研究所引进浙江红花油茶优树穗条,在青田县大垟山林场开展浙江红花油茶高接换冠试验,分析砧木林郁闭度、坡位、砧木生长势及接穗保存时间等因素对嫁接成活率的影响。结果表明,林分郁闭度在0.3~0.7之间,随着郁闭度增加嫁接平均成活率提高;郁闭度在0.7~0.9之间,随着郁闭度增加,嫁接成活率降低;当郁闭度为0.7时,嫁接成活率最高为88.8%。山腰的嫁接成活率高达86%,显著高于山顶和山脚。浙江红花油茶砧木生长势越强嫁接成活率越高。接穗于采集当天嫁接效果最好成活率达89.1%,接穗保存1、2、3、4、5、6天嫁接,成活率分别为85.2%、75.2%、51.6%、28.1%、12.2%、9.3%。偏相关分析表明,各因素对嫁接成活率影响由大到小依次为接穗保存时间(-0.97)、郁闭度(0.85)、生长势(0.81)、坡位(-0.65)。     

沙生灌木沙漠葳引种栽培试验

通过对沙漠葳的引种驯化途径及不同基质对引种成活率和苗木生长的试验研究,结果表明:沙壤土既利于保苗,也对苗木生长有利,沙漠葳在当地具有较好的适应性,但受低温影响不能正常开花结实。     

抗蒸腾剂对枣苗失水率与移栽成活率的影响

研究了1年生灰枣嫁接苗在晾晒失水过程中,喷施不同体积分数的薄膜型抗蒸腾剂对其失水率和移栽成活率的影响.结果表明,苗木移植前喷洒50,100 mL.L-1的抗蒸腾剂,能有效地降低枣苗的失水率;抗蒸腾剂50mL.L-1时,枣苗的移栽成活率达到最大.作者提出了枣苗成活的根系和茎干失水率阈值分别为30%和8%.     

杨树生长量与滩地高程关系的研究

根据同一滩地、不同高程杨树林一个轮伐期的定位观测,杨树造林保存率和材积生长量均随滩地高程降低、淹水时间增加而减小。东南湖滩地根据其杨树宜林性分为3类:①高位滩地,适于建速生丰产林基地;②中位滩地,可作一般用材林、防浪林、抑螺林的造林;③低位滩地,一般不宜直接用于杨树造林。     

海水鱼类室内育苗与室外育苗对比试验

为建立一套海水鱼类人工育苗技术,分别采用室内水泥池、室外对虾高位池以及室内水泥池与室外对虾高位池相结合的育苗方法进行美国红鱼、花尾胡椒鲷等鱼类人工育苗试验。结果表明:室内水泥池育苗成活率为11%～98 8%,室外对虾高位池育苗成活率最高为6%,室内外相结合育苗的成活率为37 5%～73%。采用前期室内人工培育,幼苗体长约10mm移到室外对虾高位池培育,既可提高育苗成活率,又可降低育苗成本,是目前值得推广的育苗方法。     

河流弧菌在天然海水与人工海水中的饥饿效应

对数生长期河流弧菌分别悬浮于天然海水和人工海水后于28℃进行饥饿试验.在饥饿初期,两种海水中河流弧菌的总菌数、活菌数、菌落形成单位数都明显上升,但天然海水中的河流弧菌生长时间持续更久、增长幅度也更大;饥饿中、后期,总菌数都保持稳定,而可培养菌数与活菌数逐渐下降,其中可培养菌数下降幅度高于活菌数,人工海水中的河流弧菌下降幅度高于天然海水.河流弧菌对青石斑鱼表皮粘液的粘附量随着饥饿时间延长先上升后下降.与对数生长期相比,饥饿60 d的可培养细胞对热和紫外线的耐受性提高.饥饿细胞的间接ELISA最低检测限高于对数生长期细胞.通过SDS-PAGE分析菌体蛋白发现饥饿细胞的蛋白质条带减少.腹腔注射饥饿60 d的河流弧菌不会引起小鼠死亡,而对数生长期细胞能够引起小鼠死亡.研究结果表明,河流弧菌能够在温暖的人工海水和天然海水中长时间饥饿存活,但是饥饿细胞的毒力较低.     

Assessment of dietary lecithin and cholesterol requirements of mud crab, Scylla serrata, megalopa using semi-purified microbound diets

The effects of varying dietary lecithin and cholesterol levels on growth, development and survival of mud crab, Scylla serrata, megalopa were evaluated using six semi‐purified, microbound diets formulated to be iso‐energetic and containing three levels of supplemental lecithin (0, 20 and 40 g kg⁻¹ diet dry weight) and two levels of supplemental cholesterol (0 and 7 g kg⁻¹ diet dry weight). Fifteen megalopa were reared individually in each treatment and the nutritional value of diets was assessed on basis of mean dry weight and mean carapace width of newly settled first crab stage, as well as development time to the first crab stage and overall survival. A significant interaction between supplemental dietary lecithin and supplemental dietary cholesterol was found for final mean dry weight of newly settled crabs, and highest survival (60%) was recorded for megalopa fed diets containing the highest levels of dietary lecithin (39.7–44.1 g kg⁻¹) (diet 5 and 6) regardless of whether diets were supplemented with cholesterol; this rate of survival was identical to that of megalopa fed live Artemia nauplii. The results indicate that supplemental dietary cholesterol may not be essential for mud crab megalopa when fed diets containing sufficient levels of supplemental dietary phospholipids.     

Inhibitory effect of 2,4-dibromophenol and 2,4,6-tribromophenol on larval survival and metamorphosis of the sea urchin <Emphasis Type="Italic">Strongylocentrotus nudus</Emphasis>

ABSTRACT:   As a possible factor leading to the low recruitment level of sea urchins in kelp forests, the inhibitory effect of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP) released from the large perennial brown algae Ecklonia kurome and Eisenia bicyclis on survival and metamorphosis of eight-armed larvae of the sea urchin Strongylocentrotus nudus was examined. The percentage of larvae that underwent metamorphosis in filtered sea water after 1 h exposure to one-half dilution of saturated dibromomethane solution (∼60 ppm) as a chemical inducer reached approximately 100% after 1 h, while that in filtered sea water containing 1 ppm TBP was reduced to 73%. This was further reduced to less than 40% in the presence of 10 and 20 ppm TBP after 2 h. In filtered sea water containing 1 and 10 ppm DBP, the proportion of metamorphosed larvae was reduced markedly to 43 and 5% after 2 h, respectively. All larvae exposed to 50 ppm TBP and to 20 and 50 ppm DBP died after 1 h. These findings suggest that DBP is more toxic than TBP for sea urchin larvae, strongly inhibiting their metamorphosis.