Tree replacement patterns in subalpine Abies-Betula forests,Wolong Natural Reserve,China

Vegetation in canopy gaps of two old-growth Abies-Betula forest stands, one with bamboo the other without, was measured. The structure of gap vegetation at each site was used to derive tree replacement probabilities. Transition probabilities indicate different tree replacement trends in forests with bamboo compared to those without. Projected compositions show Betula to be the most abundant species in bamboo stands while Abies remains most abundant where bamboo was absent. A dense bamboo sward seems to reduce the probability of Abies filling gaps by inhibiting establishment and growth of seedlings. Bamboo preempts space after canopy gap formation by increasing shoot production which reduces opportunities for establishment and growth of other woody species. Differences in dispersal ability and longevity of Abies and Betula appear to be important factors contributing to their coexistence forests with a small canopy gap disturbance regime.     

Bamboo germplasm screening with nuclear restriction fragment length polymorphisms

Summary Bamboo species are difficult to identify because flowering material is seldom available and taxonomy is of necessity based on vegetative characters. To evaluate the utility of restriction fragment length polymorphism (RFLP) analysis in bamboo systematics and germplasm screening, a library of random genomic probes from a Phyllostachys nigra PstI library was constructed. Probes from the library were used to screen bamboo germplasm consisting mostly of temperate bamboos of the genus Phyllostachys. RFLP variation was abundant, and species-specific patterns were readily obtained. Chloroplast DNA showed little variation among the bamboo accessions analyzed.     

Carbonisation of oil palm trunks at moderate temperatures

Thousands of tonnes of dry oil palm trunks will be produced annually in Malaysia after about 1990. A project was initiated to study the feasibility of converting palm trunks into charcoal. Carbonisation was done at terminal temperatures of 400–550°C with holding times of 1–3 h and at two heating rates. From laboratory-scale pyrolysis studies, it was found that holding time does not affect the quantity and quality of the charcoal produced, while heating rate has a minor influence. However, as terminal temperature increases, both yield and volatile content decrease while the fixed carbon content increases. The calorific value and ash contents are independent of the parameters studied and their respective values are 4032 kcal/kg and 37.2%. Since the calorific value is low and the ash content high, it is concluded that oil palm trunks are not suitable for the production of charcoal fuel.     

中国小竹鼠生态的初步研究

小竹鼠在我国仅分布于云南西部热带亚热带地区。主要生活于山坡稀树灌丛、阔叶林、橡胶园及居民点附近。在盈江县分布于海拔300-950米地带。取食、休息、繁殖主要在洞道内。洞系由洞口、取食道、趋避道、窝及“厕所”组成。食物主要有棕叶芦、芦竹及三叶橡胶等18种,尤喜食橡胶树主根,因而对橡胶树危害很大。13号标本中雌7雄6。在盈江每胎2-3只,以2只为多。成年小竹鼠过独居生活,雌雄各有自己的洞系。     

Initiation and development of wound tissue and roots on hypocotyl cuttings of Pinus sylvestris in vitro

The rooting of hypocotyl cuttings from 20-day-old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became.
Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed.     

四川王朗自然保护区大熊猫主食竹——缺苞箭竹(Fargesia denudat)不同发育时期酯酶和α-淀粉酶同工酶的研究

通过聚丙烯酰胺凝胶电泳,对生长在亚高山地带的大熊猫主食竹的实生苗、成竹和开花竹中不同发生年龄鞭系,以及同一鞭系内一系列生长年龄竹株作了酯酶、α-淀粉酶同工酶的比较研究。结果表明,同一竹种的不同发生年龄鞭系之间叶酯酶电泳类型存在明显差异,而同一鞭系内α-淀粉酶同工酶的变化表现与竹株生长年龄有关。由此认为,上述同工酶系统可以用作竹类无性系发育分析的生理指标。     

High-frequency embryogenesis inBrassica campestris microspore culture

Microspore culture is a very important and useful tool in plant breeding for haploid production and has been developed for many years.Brassica campestris (Brassica rapa L. ssp.oleifera) is an important oilseed crop, but it is relatively recalcitrant in tissue culture including microspore culture. The microspore culture in our laboratory is based on the Canadian protocol. Thirty genotypes ofB. campestris were included in this study; twenty produced embryos. The highest yield was 5930 embryos per 100 buds from Canadian genotype Cv-2, this result was one of the best that had been reported in microspore culture inB. campestris. The buds measuring 2.0 mm to 3.9 mm in length responded best to produce embryos, the optimum timing for microspore culture was confirmed to be during the mid-late to very-late uninucleate stage. The buds could be removed from either the main raceme or lateral racemes. Activated charcoal (150 mg l^-1) was added to the liquid NLN medium, it promoted embryogenesis significantly; embryo development was faster and the embryo yield was significantly higher than those cultures without activated charcoal. The donor plant condition was considered an important factor influencing embryogenesis; older donor plants (older than five weeks) and a cold treatment are recommended.     

A study of genetic variation and evolution of Phyllostachys (Bambusoideae: Poaceae) using nuclear restriction fragment length polymorphisms

Phylogenetic and taxonomic difficulties are common within the woody bamboos, due to their unique life cycle, which severely limits the availability of floral characters. To addresss some of these problems, 20 species of woody bamboos in the genus Phyllostachys were analyzed using nuclear restriction fragment length polymorphisms (RFLPs). The RFLP data were used to generate genetic distances between all pairs of taxa and to examine the degree of genetic variation within and among bamboo species. The genetic distances were also used to create dendrograms of accessions and species. These trees supported the current division of the genus into two sections and provided some information on the thorny taxonomic problems in this group. We show that RFLPs can be used for species identification and the delineation of species limits.