Forest Fire in Early Holocene Forest Changes at Lake Barrine,Australia

Fire is one of major factors in forest ecosystem. This paper presents results of charcoal and pollen analysis on Early Holocene sediments in Lake Barrine, Australia. Time series analysis and mathematical modeling were used to infer patterns of forest fire, relationship between fire and major vegetation elements and the roles forest fire played in forest changes. The analysis shows that in Early Holocene fire frequencies in this area decreased from one major fire in less than 50 years in the early Eucalyptus forest stage (zone S1) to one in 230 years in the later stage (zone S2). After the establishment of rainforest, fire activities were much weaker. The effects of fire on three major elements of Eucalyptus forest varied according to their different fire adaptive traits. In process of the change from Eucalyptus, forest to rainforest, fire protected-the former and delayed.the establishment of the later.     

Exogenous Ca2+ Regulation of Pollen Tube Growth and Division of Generative Nucleus in Nicotiana tabacum

Cytological and statistical studies on the effects of exogenous Ca2 + on in vitro pollen tube growth and generative nucleus (GN) division of tobacco (Nicotiana tabacum L. ) were conducted in an artificial experimental system. Under normal cultured conditions, the rate of GN division increased logarithmically in general, and reaches the climax at about 10 - 18 h. Among the treatments with various Ca2 + concentrations, 10- 3 mol/L was the optimal concentration for pollen tube growth, whereas other Ca2+ concentrations showed increasing inhibitory effect with the time of culture. Generally, Ca2 + concentrations at 10-2 and 10-3 mol/L favored GN division more than the others. Compared with 10-3 mol/L Ca2 + concentration at 10-2 mol/L benefitiated GN division at earlier stage of the treatment, but afterwards showed inhibitory effect gradually. Besides, the authors designed another series of experiments, in which 10-2, 10-1 mol/L Ca2+ (final concentrations) or 2,10 mmol/L EG-TA was respectively added to the medium containing 10-3 mol/L Ca2+ at 10 h of culture. Pollen tube growth was inhibited by the high Ca2+ treatments, especially being severely effected by 10-l mol/L Ca2 + from which wall, thickening of the tube tip, amitotic division of GN leading to micronucleus formation occurred. 10-2 mol/L Ca2 + treatment, however, promoted GN division at the earlier stage of treatment ( 10 - 12 h). EGTA treatments inhibited both pollen tube growth and GN division.     

Establishment of Transfer Functions of the Pollen-Climatic Factors in Northern China and the Quantitative Climatic Reconstruction at DJ Core

The 2.4 meter-long core was extracted from the Diaojiao lake (41º18′N, 112º21′E) at the foot of the northern part of Daqingshan Mts. Pollen analysis from collections subsampled in the laboratory at 2 cm intervals, revealed plentiful pollen and spores from over 10 arboreal genera, including Pinus, Betula, Picea, Abies, Carpinus, Quercus, Ulmus and more than 20 non-arboreal genera, mainly of Artemisia, Labiatae, Nitraria, Polygonaceae, Ranunculus, Thalictrum, Umbel- liferae, Caryophyllaceae and Cyperaceae. Fern spores, aquatic pollen and algae were also observed in some parts of the core. The transfer functions were established by the stepwise regression analysis using the climatic factors and 13 pollen taxa. The different Fl and F2 value were used as the thresh- old value of F test (i. e. used for selecting and deleting factors). Each regressed equation was obtained from 70 times of calculations with a step-wise increase of 0.1 for Fl and F2 and those having the smallest regression deviation and the largest multiple correlation coefficient were the final four transfer functions. Substituting the pre-factor obtained from the stratigraphic sampled into the regression equations, the estimates of temperature and precipitation in January and in July, and annual mean temperature values could be calculated. Some climatic stages were inferred from total pollen influx and pollen percentage from the core using a transfer function: humid-cool (from 10 000 to 7 800 a BP), arid-cold (9 200 to 7 900 a BP), arid-warm (7 900 to 7 100 a BP), humid-warm (7 100 to 4 400 a BP), arid-warm (4 400 to 3 000 a BP), arid-cold (3 000 to 2 100 a BP). The highest annual mean temperature during Holocene was ca. 4 ℃ higher and the lowest was ca. 2 ℃ lower than the present temperature. Annual precipitation was 250 mm higher and 300 mm lower than the present.     

Positional Shift Between the Vegetative Nucleus and the Generative Cell in Amaryllis Pollen Tube

A modified technique, FITC-tubulin immunofluorescence and DAPI localization to demonstrate simultaneously both the generative cell (GC) and the vegetative nucleus (VN) in the pollen tube under ultra-violet excitation, was developed sucessfully. During the germination of the pollen tube of Amaryllis vittata Ait. the GC and the VN, either being the first one, entered the tube within the first 1—2 h from the pollen grain. However, before the time of GC division, the VN was always positioned distally near the tip of the tube. In case when the GC entered the tube first, then the VN must have a positional shift in order to pass over the GC. The detail processes of positional shift between the GC and the VN were observed. Three basic processes were demonstrated: 1. The anterior end of the VN first reached the vicinity of the posterior attenuated extension of the GC about 2 h following germination forming a temporal physical association. Sometimes their both ends could be inserted into one another for certain extent. 2. The whole VN moved forward and contacted in parallel with the GC until they became twisted together and 3. The VN passed over the GC and greatly elongted lengthwise. Its posterior part became inserted into the anterior end of the GC. The behavior of positional shift between the VN and the GC in the pollen tube seems to be an adjustment of their diameters to fit the narrow tube. A conclusion may be drawn that the rate of movement between the VN and the GC was apparently different during the passage through the tube. Such difference may presumably be accompanied by the independent motive mechanism and structural difference between the VN and GC themselves, which provide their motive force for movement in the tube.     

三蕊草属Sinochasea Keng系统位置的研究

叶片表皮、叶片横切面、花粉和淀粉粒的微观特征,对青藏高原的特有类群三蕊草属Sinochasea Keng的系统位置进行了探讨。结果表明,三蕊草S.trigyna Keng在上述微观性状上与毛蕊草Duthiea brachypodia(P.Candargy) Keng et Keng f.差距最小,与冠毛草Stephanachne pappophorea(Hack.)Keng差距次之,与宝兴野青茅Deyeuxia moupinensis(Franch.) Pilger和拂子茅Calamagrostis epigeios(L.) Roth差距最大;三蕊草属的系统位置应处于毛蕊草所隶的燕麦族Aveneae中;在系统演化上,燕麦族是最原始的类群,它可能直接或间接地派生了针茅族Stipeae和剪股颖族Agrostideae。     

稠李属(Padus Mill.)花粉形态研究

首次报道中国稠李属花粉形态研究,结果表明:花粉粒形态、大小和外壁纹饰可作为划分种的依据。由此可区分为:花粉粒32.0×25.5μm、条纹细弯、穿孔明显的是亚洲稠李(P.asiatica Kom.);花粉粒37.5×17.7μm、体积大、穿孔多的是光叶亚洲稠李(var.subglabra Y.L.Hanet C.Y.Yang var.nov.);花粉粒32.0×24.4μm、条纹细直、穿孔少量的是欧洲稠李(P.aviummill.);花粉粒21.0×22.1μm、条纹宽、直、穿孔不明显,即北京稠李(P.beijingensis Y.L.Hanet C.Y.Yang sp.nov.),(新种已另文发表)。     

A New species of the Genus Tupistra (Convallariaceae), with Reference to Its Karyotype and Pollen Morphology

A species of the genus Tupistra,T．pingbianensis J．L．Huang et X．Z．Liu,is described as new,and its karyotype and pollen morphology are reported． The bimodal karyotype of this species is formulated as 2n＝38＝14m+10sm+8st+6t,and pollen grains are spheroidal,inaperturate,with rugulate exine sculpture．Based on its floral structure,karyotype and pollen morphology,T．pingbianensis J．L．Huang et X．Z．Liu is considered phylogenetically closely related to T．fungilliformis Wang et Liang．Whether the repense rhizome,solitary leaves of T．pingbianensis J．L．Huang et X．Z．Liu indicate a close relationship between the genus Tupistra and the genus Aspidistra needs further studies．     

高粱九个性状遗传参数的分析

1991─1992连续两年,在水、旱地两种环境条件下,对20个品杂种,9个性状进行了3个遗传参数的分析。从遗传进度的估算中确定了较高增量的性状。在遗传相关的分析中,又得出14对性状遗传相关系数较高,表现型相关系数水、旱地都达到显著水准。但在相关遗传进度的估算中,其增量幅度旱地明显地小于水地,这说明旱地培育高产品种的困难较大。通过对12 4个指数项目的分析,提出了水、旱地育种各自应采用的较好的选择方案。     

Protein Electrophoresis of Single Pollen Grains of Hibiscus rosa-sinensis

Electrophoresis and staining of proteins from the single pollen grains of Hibiscus rosasinensis have been developed by using general ultrathin polyacrylamide gel combined with highly-sensitive silver staining technique. The result revealed that the pollen abortion could occur in different stages of pollen development. The protein patterns varied greatly in different stages of pollen development, even in the different pollen grains in the same anther at the same development stage. Some bands exhibited a disjunction by classical Mendelian ratio 1: 1, suggesting that the gene loci were heterogeneous and the proteins were related to the expression of the genes at the early stage of pollen development.     

Observation of Pollen Tube Behaviour and Early Embryogenesis Following Interspecies Pollination Between Actinidia deliciosa and A. arguta

The pollen tube behaviour in the style and early embryogenesis following interspecies pollination between Actinidia deliciosa No. 26 and A. arguta were observed by means of fluorescence and light microscopy. Pollen grains germinated on the papillate stigma and pollen tubes grew along the V-shaped open-type style. Pollen tubes showed slower growth and reached the ovules 50--60 hours later than those of the control. Several abnormalities of pollen tubes have been observed at the base of the style, including wave-like pollen tubes, pollen tubes with swollen or pointed tips, with variable diameters, and a few with irregular growth. Random deposition of callose along pollen tube wall and even the whole wall was observed. About 26.74 % of the ovules were successfully fertilized and developed into seeds, among them 68.50% of the seeds were normal and 31.50% were abortive. About 11.41% were empty seeds without embryo and endosperm. Unfertilized small ovule was 61.45 %. Normal seed and its embryo were smaller than those of the control. The development of embryo was of the Soland type. The endosperm was cellular. The zygote remained quiescent for about 12-15 days before it started to divide, eventually forming a cotyledonary embryo 50 days after pollination.