PEG高渗预处理对番茄种子活力的影响

利用－１．０ＭＰａ聚乙二醇（ＰＥＧ）─６０００水溶液预浸已干燥的番茄种子，再度干燥后立即播种发芽，可以提高种子发芽速度和整齐度，增加正常苗数，减少休眠种子数，明显地提高种子活力水平．但是，上述处理的种子经５个月短期贮藏后，原来所获得的处理正向效应基本上丧失．与未处理对照相比，甚至还表现出某种程度加速劣变的作用．相反使用同样浓度ＰＥＧ处理未经干燥的新鲜湿种子，无论是经贮藏或不经贮藏，均可明显地提高处理种子活力．     

In vitro pollen germination in avocado (Persea americana Mill.): Optimization of the method and effect of temperature

An improved in vitro pollen germination method was developed for avocado (Persea americana Mill.). The effect of different concentrations of sucrose, polyethylene glycol (PEG), Mg and Ca on pollen germination was evaluated in order to determine the optimal pollen germination medium, i.e. that maximizing the percentage of pollen germination and minimizing the percentage of bursted pollen grains. Once the germination medium was optimized we used it to study the effect of temperature on in vitro pollen germination and tube growth in different cultivars from the three botanical varieties of avocado, that differ in their adaptation to environmental conditions. Significant differences in percentage of pollen germination and in pollen tube growth were observed among cultivars. These results could have implications not only for optimizing pollen management in avocado but also to select the best pollinizers for a particular cultivar.     

Effect of hot air,UV-C,white light and modified atmosphere treatments on expression of chlorophyll degrading genes in postharvest broccoli (Brassica oleracea L.) florets

Several treatments were applied in order to delay postharvest degreening in broccoli florets and investigate their effects on genes associated with chlorophyll catabolism. Degradation of chlorophylls is the most evident visual manifestation of broccoli postharvest deterioration, occurring rapidly due to the immature stage in which the material is harvested. Treatments such as storage in modified atmosphere, exposure to hot air, UV-C and white lamps were employed in the current work to induce a delay in degreening and chlorophyll degradation. Expression of genes possibly related to chlorophyll catabolism was analyzed in these samples and discussed. Chlorophyllases, the enzymes traditionally believed to remove the phytol side chain from chlorophyll appear to have a gene expression that was not regulated by postharvest treatments. Pheophytinase, a recently discovered new enzyme in this metabolic pathway, correlated chlorophyll loss accurately in heat, UV-C and white-light treatments, but not in modified atmospheres. Results presented in this work indicate that postharvest treatments that delay chlorophyll degradation have a higher effect on the expression of pheophytinase rather than on chlorophyllase genes.     

Short-term effects of de-oiled olive pomace mulching application on a young super high-density olive orchard

A two-year field experiment was performed in order to evaluate the suitability of de-oiled olive pomace for soil management in a young super high-density olive orchard. In the literature there are not works on this topic.     

KH-550含量对茶梗粉/HDPE性能的影响

为探明硅烷偶联剂KH-550对茶梗粉/HDPE复合材料相容性与分散性的改善效果,用国家标准方法和HAAKE MARSⅢ旋转流变仪对复合材料的力学性能与流变性能进行了研究。结果表明,KH-550含量为1.8%时,复合材料的力学性能与耐水性能较好;相同应变条件下,复合材料的储存模量和损耗模量均随KH-550的增加而降低,当KH-550含量为1.8%时,复合材料的储存模量和损耗模量均达到最小值;相同温度和频率条件下,复合材料的储存模量随KH-550的增加而减小,且均在KH-550含量为1.8%时达到最小值。KH-550含量为1.8%时,复合材料的力学性能、耐水性能、界面相容性以及分散性等综合性能较好。     

Effect of propylene glycol and undegradable protein source on rumen fermentation, blood metabolism and milk production in lactating dairy cows

Eight lactating Holstein cows were divided into two groups ( n  = 4) and used in a double reversal trial with three periods of 14 days each, to evaluate diets containing propylene glycol (PG) and ruminally undegradable protein (RUP) blend on milk yield and composition, ruminal fermentation and blood metabolism. The control diet contained 20% chopped Sudangrass hay, 20% cubed alfalfa hay, 12% corn silage, and 48% of the respective concentrate mixtures (dry matter basis). The experimental diet (PG + RUP) partially replaced the concentrate mixture from the control diet with 1.4% PG and 2.1% RUP. Both diets contained about 16% crude protein and 71% total digestible nutrients. Dry matter intake was similar between the two diets. Daily production of milk, milk lactose and milk solids-not-fat increased by 9.0%, 11.3% and 9.3%, respectively ( P  < 0.1), for cows fed diets with PG + RUP; milk composition was unchanged. Although the concentration of ruminal total volatile fatty acids was unchanged, the proportion of propionic acid increased, and the proportion of acetic acid decreased with PG + RUP. The concentration of ruminal ammonia nitrogen and number of ciliate protozoa was not significantly affected by PG + RUP. The concentration of glucose in blood plasma increased, the concentration of urea nitrogen was unaffected, and the concentration of some essential free amino acids decreased with PG + RUP. It is suggested that these changes might be caused predominantly by PG, and the addition of PG may exert a favorable effect on milk production through increased metabolism.     

渔用自增强聚乙烯单丝的拉伸力学性能分析

在标准实验室环境里,对渔用自增强聚乙烯(self-reinforced polyethylene,简称SRPE)单丝的结晶形态、拉伸力学性能进行了分析。结果表明：渔用SRPE单丝结晶度、声速值比普通聚乙烯(polyethylene,简称PE)单丝均有提高,其内部生成了串晶结构;SRPE单丝断裂强度、结节强度和结强损失率比普通PE单丝分别提高了12．75％、4．82%和12．69％,而断裂伸长率降低了27．72％。结论可供渔具设计及网线材料选配时参考。     

Properties of PEG/thermally modified wood flour/polypropylene (PP) composites

In order to improve the dimensional stability of wood-polymer composites, wood flour pre-treated by polyethylene glyco1 (PEG) at two different concentrations and then thermally treated at 140°C, was used as raw material to produce wood flour/polypropylene (PP) composites at a wood content of 40%. The structure of modified wood flour was analyzed with a scanning electron microscope (SEM) and its effect on the physical and mechanical properties of wood flour/PP composites was evaluated. The SEM results indicated the "bulking" effect of PEG on wood flour, which resulted in reduced water uptake. The combination of PEG and heat treatment further improved the moisture resistance of the composites. However, PEG modification had a negative effect on the flexural modulus of rupture (MOR) and the modulus of elasticity (MOE); whereas heat treatment partly compensated for this reduction. For dynamic mechanical properties, PEG treatment decreased the storage modulus (E′). However, the heat treatment resulted in an increase of E′ of the wood flour/PP composites, with the temperature of loss factor peaks shifting to a higher temperature.     

PEG-6000干旱胁迫对沙芦草种子萌发特性的影响及其抗旱性评价

采用不同浓度PEG-6000模拟干旱胁迫的方法对7份不同来源的沙芦草种质的种子萌发特性及其抗旱性进行鉴定和评价.结果表明:不同浓度PEG-6000胁迫对沙芦草种子的相对发芽率、相对发芽势、相对抗旱指数、相对活力指数、相对幼苗长、相对幼苗重均有明显抑制作用;低浓度PEG-6000干旱胁迫对相对幼根长具有促进作用,高浓度具有抑制作用.在PEG干旱胁迫下,7份沙芦草种子的相对发芽率、相对发芽势、相对幼苗长和相对根长差异较大,而相对抗旱指数、相对活力指数和幼苗重差异较小.通过隶属函数法综合评价认为,7份沙芦草种质材料的抗旱性顺序依次为3号＞7号＞2号＞4号＞6号＞l号＞5号材料.