Cementing mechanism of algal crusts from desert area

34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the same sandy soil and the same place (37degrees27'N, 104degrees57'E). Their different cohesions both against wind force and pressure were measured respectively by a sandy wind-tunnel experiment and a penetrometer. On the basis of these algal crusts, the cementing mechanism was revealed from many subjects and different levels. The results showed that in the indoor artificial crusts with the weakest cohesion bunchy algal filaments were distributed in the surface of the crusts, produced few extracellular polymers (EPS), the binding capacity of the crusts just accomplished by mechanical bundle of algal filaments. For field crusts, most filaments grew toward the deeper layers of algal crusts, secreted much more EPS, and when organic matter content was more than 2.4 times of chlorophyll a, overmuch organic matter (primarily is EPS) began to gather onto the surface of the crusts and formed an organic layer in the relatively lower micro-area, and this made the crust cohesion increase 2.5 times. When the organic layer adsorbed and intercepted amounts of dusts, soil particles and sand grains scattered down from wind, it changed gradually into an inorganic layer in which inorganic matter dominated, and this made the crusts cohesion further enhanced 2-6 times. For crust-building species Microcoleus vaginatus, 88.5% of EPS were the acidic components, 78% were the acidic proteglycan of 380 kD. The uronic acid content accounted for 8% of proteglycan, and their free carboxyls were important sites of binding with metal cations from surrounding matrix.

Growth of juvenile Chinese sturgeon Acipenser sinensis fed live and formulated diets

Triplicate groups of 3.8-g juvenile Chinese sturgeon Acipenser sinensis were reared for 8 weeks in indoor flow-through systems on one of four diets: a natural diet consisting solely of live tubificid worms, a semimoist practical diet, a dry practical diet, and a purified diet. The formulated diets were prepared in the laboratory and had protein contents of 47-50%. Except for the group fed the purified diet, fish showed high survival (94-96%) and growth (final weight, 41-45 g). Survival and specific growth rate did not differ significantly between groups fed the natural, semimoist, and dry practical diets, but were significantly (P < 0.05) lower in fish fed the purified diet. Proximate analysis showed that fish fed purified diet had lower protein and lipid levels but a higher moisture content than fish fed other diets. Our results demonstrated that growth and survival of cultured juvenile Chinese sturgeon fed practical diets were comparable with those fed live tubificid worms. However, Chinese sturgeon fed a purified diet showed inferior growth and survival.

草本植物对土质路面径流水动力学特征及水沙过程的影响

通过室内人工模拟降雨,研究了草本植物不同覆盖度土质路面的径流水动力学特征以及路面的产流产沙过程。结果表明,路面径流的弗劳德数和雷诺数属层流的急流范畴,并且二者与径流流速及过水断面单位能量相同,均随草本植物覆盖度的增大而减小。而Darcy-weisbach阻力系数以及曼宁糙率系数则均随覆盖度的增大而增大。在不同覆盖度土质路面上,径流量随径流时间急剧增大后趋于稳定,且二者符合移轴双曲线关系,而输沙率则经历了先增大后减小的过程。随着植被覆盖度的增大,土质道路的水分入渗率逐渐增大,而径流量、输沙率及含沙率均逐渐减小。该研究表明土质路面种植的草本植物具有较好的水土保持功能,为阐明草本植物与土壤侵蚀的关系提供了理论依据。

薄层水流水力特性试验研究

对粘砂床面的薄层水流进行定床试验,研究了不同流量、坡度下薄层水流的水力学参数(流态、水深、流速及阻力系数)随坡度和流量的变化规律。结果表明:水流雷诺数Re随着坡度和流量的增大而增大,但Re主要是由流量决定的,坡度对Re的影响不大,水流流态基本上在过渡流区和紊流区;平均水深-单宽流量,流速-单宽流量,水流阻力系数-单宽流量均成很好的幂函数形式,平均水深和流速均随单宽流量的增大而增大,阻力系数随着单宽流量的增大而减小。

花椒水浸液及酚酸类化感物质对作物种子萌发和幼苗生长的影响效应

花椒（Zanthoxylum piperitum）是川西干旱河谷地区的重要经济作物，化感作用是花椒连作障碍的原因之一。系统研究花椒化感作用有助于深入理解并最终解决花椒连作障碍。本文通过研究花椒叶、林下土壤浸提液及单一纯化感物质对花椒幼苗生长、苜蓿种子萌发及幼苗生长的影响作用，从生理生化角度揭示浸提液及纯化感物质的作用方式。通过室外和室内模拟实验，对浸提液及纯化感物质的化感效应进行比较，为花椒连作障碍的解决和化感作用机制的深入理解提供依据。主要结果如下： 1.花椒叶及林下土壤浸提液对地下生物量影响作用强与对地上生物量的化感效应，两种浸提液的化感效应强度不同，叶浸提液作用表现更显著。其中在Y6、Y8 、T6和T8处理时，花椒幼苗地下生物量分别降低了31.2%、32.1%、31.6%和31.7%。 2.两种浸提液均能显著影响花椒幼苗体内的保护性酶活性，总体说来，在高浓度下抑制各种抗氧化物酶活性，幼苗体内丙二醛含量增加，幼苗受害严重；在较低浓度下，各种保护性酶活性有所增加，丙二醛含量减少，幼苗伤害减轻。同时，不同月份里，各种酶的活性高低显著不同，9月份的活性显著低于7月份的酶活性。对于养分含量的影响，Y8、T8的影响强度最大，分别使碳元素含量降低了27.8%和30.8%，使钾元素含量降低了34.7%和25.6%。 3.花椒叶及林下土壤浸提液对苜蓿种子萌发及幼苗生长有化感作用，表现在最终萌发率、不同物质代谢及保护性酶活性的差异上。两种浸提液对苜蓿种子萌发过程中蛋白质的含量均无显著性影响，对淀粉和可溶性糖的影响作用类似，高浓度处理无明显化感效应，较低浓度处理显著降低二者在萌发苜蓿种子中的含量。Y2、Y4与T4处理分别使可溶性糖含量减少了32.3%、29.1%和18.8%，Y2与T2处理分别使淀粉含量降低了29.3%和26.8%。 4.苜蓿种子在4种单一化感物质最高浓度即10-3 mol•L-1处理下，萌发率显著降低，半数萌发时间推迟，随着处理浓度降低，抑制作用逐渐减弱，当降低到10-6 mol•L-1时，又能够表现出对苜蓿种子萌发的促进作用。 5.纯化感物质在10-6 mol•L-1时使苜蓿幼苗叶片的保护性酶活性显著升高，丙二醛含量显著降低；在10-3 mol•L-1时使苜蓿叶片中保护性酶活性显著降低，丙二醛含量增加，膜脂过氧化程度加重。 Zanthoxylum piperitum is one of the most important cash crops and has been extensively cultivated in Eastern Tibetan Plateau, especially in the fragile dry valley areas. Allelopathic effects could be a reason for Z. piperitum’s continuous cropping impediment. Systemmatically research of the effect of Z. piperitum allelopathy could help to comprehend the continuous cropping impediment. The allelopathic effects on seedlings growth and seed germination of aqueous extracts of Zanthoxylum piperitum and phenolic allelochemicals were studied, and the action mechanism of the two substances was also discussed from physiology. Indoor and outdoor experiments were set to compare the difference between aqueous extracts and pure allelochemicals. The main results showed that: 1. The aqueous extracts of leaf and soil had significant allelopathic effects on aboveground and underground biomass, but the effect on underground biomass was stronger than the effect on underground evidently. Treated with Y6、Y8 、T6 and T8, the underground biomass was reduced 31.2%、32.1%、31.6% and 31.7% respectively. 2. The activity of activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase were significantly reduced, while the content of MDA was increased and the seedlings were suffered stronger, when treated by the high concentration; but at the low concentration, these were reversed. And then, at the different month, the activities of antioxidant enzyme were significantly distinct. As for the contents of nutrient element, Y8、T8 had the more intensive effects than other treatments. 3. The results showed that the two types of aqueous extracts had significant allelopathic effects on seed germination, substances metabolize and the activity of antioxidant enzyme. But the aqueous extracts had no effects on the content of protein, while had the similar effects on the content of starch and soluble sugar. At Y2、Y4 and T4, the content of soluble sugar decreased 32.3%、29.1% and 18.8% respectively. 4. Treated with 10-3 mol•L-1 of the four allelochemicals, the seed germination of alfalfa was significantly inhibited. Ferulic acid, coumarin and vanillic acid at 10-3 mol•L-1 significantly reduced the activities of antioxidant enzyme, while the content of MDA in alfalfa seedling was significantly increased. The restrain effects became weakened with the treat concentration falled. However, ferulic acid, coumarin and vanillic acid could increase the activities of antioxidant enzyme at 10-6mol•L-1.

新型土壤结构改良剂水分特性及其对玉米苗期的影响研究

试验采用室内研究的方法,探讨2种以环境废弃资源为主要原料的新型土壤改良剂的基本水分特性,验证其对玉米苗期的影响。试验结果表明,2种改良剂在不同溶液中溶胀度不同,PJG在蒸馏水中溶胀度最大,PFL则是在自来水中吸水能力最强。PFL的吸水速率要低于PJG,单位质量最大吸水量1.705,为PJG的46.9%。2种改良剂对玉米出苗率的影响不是很明显,但能显著地提高玉米苗期株高和叶面积,对苗期土壤水分的散失也起到了很好的抑制作用。2种改良剂都能明显提高玉米苗期水分利用效率,最优水平分别高于对照27.89%和58.99%。综合各方面结果,建议在玉米试验中使用PJG的最佳浓度为0.8%,PFL为0.05%。

新疆土壤侵蚀遥感影像判读与几个独特问题

在新疆土壤侵蚀遥感调查中，对遥感影像的判读，采用了遥感信息与地学资料相结合、综合分析与主导分析结合、室内判读与专家经验及外业调查结合、分层分类判读的方法；根据新疆水蚀、风蚀、冻融侵蚀具有垂直分布规律的特点，在土壤侵蚀分类时主要考虑降水量、海拔高度和年均温等指标；列出了新疆土壤侵蚀分类分级影像特征；指出盐碱地的侵蚀分类与戈壁的侵蚀分级是有待研究的重要问题。

中国水蚀土壤抗剪强度研究

利用野外测试数据、土壤样品的室内理化分析数据和参考文献数据 ,对水蚀区范围内水土流失过程中的土壤抗剪强度进行了初步研究 ,建立了中国水土流失土壤抗剪强度的回归模型 ,总结出水蚀区范围内水蚀过程中有关土壤抗剪强度的 3条结论 :影响水土流失过程中土壤抗剪强度的主导因素是容重、粉 /黏、土壤含水量、土壤有机质含量 ;抗剪强度随土壤类型发生有规律的变化 ;抗剪强度在中国水蚀区范围内有较明显的空间分异规律 (包括水平分异规律和垂直剖面构型规律 )

陕西壳斗科植物新类群

在大量野外调查和标本整理的基础上 ,作者对陕西省壳斗科植物的分类与分布进行了系统研究。本文报道了新变种 3个 :太白槲栎 (QuercusalienaBl.var.taibaiensisW .H .Zhang)、陕西槲栎 (QuercusalienaBl.var.shaanxiensisW .H .Zhang)、星毛木包栎 (QuercusglanduliferaBl.var.stel latopilosaW .H .Zhang) ;新组合 2个 :城口青冈 (Cyclobalanopsisfargesii(Franch .)S.Z.QuetW .H .Zhang)、粉背青冈 (Cyclobalanopsishypargy rae(Seem .)W .H .Zhang) ;陕西省分布新记录 3个 :多穗石栎 (LithocarpuspolystachyusRehd.)、大叶栎 (QuercusgriffithiiHook.f.etThoms.)、长叶木包栎 (QuercusmonnulaY .C .HsuetH .W .Jen) ;同时 ,澄清了木包栎 (Q .glanduliferaBl.)命名上的一些问题

Cultivation of the brown alga Sargassum horneri: sexual reproduction and seedling production in tank culture under reduced solar irradiance in ambient temperature

As a large conspicuous intertidal brown alga, individuals of Sargassum horneri can reach a length of more than 7 m with a fresh weight of 3 kg along the coasts of the Eastern China Sea. The biomass of this alga as a vital component in coastal water ecology has been well documented. In recent years, a steady disappearance of the algal biomass along the once densely populated coastal areas of the Eastern China Sea has drawn attention in China. Efforts have been made to reconstruct the subtidal algal flora or even to grow the alga by use of long-lines. As part of the efforts to establish an efficient technique for producing seedlings of S. horneri, in this investigation a series of culture experiments were carried out in indoor raceway and rectangular tanks under reduced solar irradiance at ambient temperature in 2007-2008. The investigation demonstrated that: (1) sexual reproduction of S. horneri could be accelerated in elevated temperature and light climates, at least 3 months earlier than in the wild; (2) eggs of S. horneri had the potential to be fertilized up to 48 h, much longer than that of known related species; (3) suspension and fixed culture methods were both effective in growing the seedlings to the long-line cultivation stage; and (4) the life cycle of S. horneri in culture could be shortened to 4.5 months, thus establishing this alga as an appropriate model for investigating sexual reproduction in dieocious species of this genus.

Transforming kelp into a marine bioreactor

The past decade has seen the genetic engineering of various types of seaweed. To date, genetic transformation studies have been carried out in several seaweeds, including the red seaweeds Porphyra, Gracilaria, Grateloupia, Kappaphyclus and Ceramium and the green seaweed Ulva. A genetic transformation model system has been established in the most commonly cultivated seaweed, the brown seaweed Laminaria japonica (kelp), based on the transfer of technology used in land plant transformation and also by modulating the seaweed life cycle. This model showed the potential for application of transgenic kelp to the production of valuable products and an indoor cultivation system for transgenic kelp was proposed, taking into account necessary factors for bio-safety. In this review, the establishment at use of the kelp transformation model is introduced, highlighting the potential for transforming kelp into a marine bioreactor.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: enhanced seedling production in tumbled culture

The reuse of holdfasts for regeneration of young seedlings or using wild juvenile plants as the seedling source has played the major role in commercial cultivation of the brown alga Hizikia fusiformis in East Asia over the past 20 years. The possibility of employing zygote-derived germlings for producing seedlings has been discussed in the literature, but has not yet become a reality. Three main obstacles have limited the use of zygotes as a main source of seedlings, (1) the dioecious nature of the algal life cycle which may lead to asynchronous male and female receptacle development and thus different timing of egg and spermatozoa expulsion, (2) the low attachment rate when using zygote-derived germlings with developed rhizoids from wild parental plants for seeding production, and (3) the problem of culturing young germlings in regions where water temperature is high in summer. In this investigation, shifting the timing of receptacle formation earlier than in nature was performed by tumbling the algae in a long-day tank (16-h light per day). Synchronization of egg and spermatozoa expulsion and thereafter fertilization were conducted in indoor tanks. Receptacle formation in constant long days could be shifted by 20 days earlier than in plants cultured on long lines in the open sea, or I month earlier than in plants growing on intertidal rocks. Synchronized expulsion of eggs and spermatozoon led to a high rate of fertilization. This was achieved by tumbling the male and female receptacle-bearing branchlets in the same tank at low density in high irradiance. In two independent trials, a total of 1,400,000 zygote-derived germlings were obtained from 620 g (fresh weight) female sporophytes. The germlings shed from the receptacles were at an identical developmental stage indicating high synchronization of expulsion of eggs and spermatozoon followed by fertilization. Approximately 63% ( +/-9.6%) of the germlings were shed from the receptacle between 16 and 24 It after fertilization and 20% ( +/-11.9%) remained on the receptacle for 3 days after fertilization. Germlings were seeded on string collectors before rhizoids started to elongate and the attachment efficiency was enhanced. Young seedlings reached 800 ( +/-50) mum in length in 25 days at 25 degreesC before they were transferred to open sea cultivation. These results provide the basis of a practical way of seedling production by use of zygote-derived germlings in the commercial cultivation of Hizikia fusiformis. (C) 2004 Elsevier B.V All rights reserved.

Photoperiodic long-day control of sporophyll and hair formation in the brown alga Undaria pinnatifida

Two photoperiodic responses, the development of sporophylls and hairs, have been quantified in sporophytes of the brown alga Undaria pinnatifida. In a final experiment, the algae were cultivated in outdoor, 2000-L seawater tanks in a greenhouse for up to 12 weeks, and daylength was regulated by automatic blinds mounted on top of the tanks. Vegetative young sporophytes were treated under short-day (SD; 8 h light per day) or long-day conditions (LD; 16 h light per day), at 12 h light per day or in a night-break regime (NB; 8 h light per day, 7.5 h dark, 1 h light, 7.5 h dark). The earliest sporophyll development was observed 6, 7 or 9 weeks under LD, NB or SD conditions, respectively. After 12 weeks the sporophylls were significantly longer and wider under LD or NB conditions than in the SD regime, and only half of the experimental algae had formed sporophylls under SD conditions, but all algae under LD or NB conditions. In a foregoing 7-week culture experiment performed in 300-L indoor tanks, enhanced sporophyll formation had also been observed under LD and not under SD conditions (NB omitted). In both experiments, blade elongation rates remained high until the end of the experiments in SD, but declined during sporophyll initiation in LD, NB or at 12 h light per day. Another difference caused by photoperiod was observed in regard to the development of surface hair spots which occurred in both experiments on the blades in LD, NB or at 12 h light per day with identical densities, but were completely lacking under SD conditions. It is concluded that U. pinnatifida is a facultatative long-day plant in regard to reproduction forming vigorously sporophylls in long days, and an obligate long-day plant in regard to hair formation.