Abstract:Two Elephantopus species and one Pseudelephantopus species have been placed inone single genus Elephantopus L. sensu lato by some earlier systematists. The genomicprofile obtained by amplifying the DNA with different single primers were distinctive tothese three species and two genera. The Similarity Indexes indicated that Elephantopus mollisis more closely related to E. scaber than to Pseudelephantopus spicatus. The present studyindicated that the Elephantopus scaber L., and its closed species E. mollis as well as Pseudetephantopus spicatus were genetically to be distinguished． The estimates of genomic DNA fingerprints based on Similarity Index values ca lculated from amplified DNA band profiles show a dose association with known levds of morphological and histological， cytological relatedness．

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Abstract:Nine species of Pteridophytes in Hong Kong are reported, of Which 2 are newrecords, viz. Osmunda banksiifolia (Presl) Kuhn and Dicranopteris linearis (Burm.) Underw.The nomenclature of 5 species, viz. Selaginella trachyphylla A. Br., Angiopteris fokiensisHieron., Osmunda vachelii Hook., Crepidomanes latemarginale (Eaton) Cop. andHymenwillum austrosinicum Ching, is revised- In addition, 2 rare and endangered species,Lycopodiella caroliniana (L.) Holub and Osmunda mildei C. Chr., are also discussed.

Abstract:Epidermal features of the leaves of 5 species in 3 genera of Calycanthaceae wereobserved under light microscope and SEM. In species of genera Chimonanthus,Sinocalycanthus and Calycanthus, the leaf trichomes all are unicellular and nonglandular,the upper and lower epidermal cells have the same shape with sinuate anticlinal walls, andthe stomata are of paracytic type, which can be attributed to the same familyCalycanthaceae. The evolutionary trend of stomata in the three genera is recognized as the guard cells at polar regions from having no T-shaped thickening to having，and the stomatal rim at both sides being from one rim to double rim.

Abstract:In the present paper the chromosome number and karyotype of Cycaschantaiangensis N. Liu are reported. It's karyotype formula is K(2n)= 22= 6m+2sm+2st+12t.

Abstract:The research on forest self-thinning has been developed greatly, and a lot oftheoretical or empirical formulations were proposed. In this paper a method of artificialneural network is introduced, and a model of three-level feedtoward back-propagationneural network to simulate self-thinning law of Pinus massoniana is established for the firsttime. The result of simulation shows that artificial neural network model can fit the observeddata very well, and it is very useful in practice, which will enrich the research method of forest self-thinning.

Abstract:Dry or germinated seeds from hybrid rice "Youza" and its parents"Qiguizao' and u Lemont" were treated by 5-10 μmol/L of methyl viologen(MV) for 24 hours. Seed vigor and seedling growth were inhibited pronouncedly butgermination rate was not disturbed. The ratio of coleoptile/radicle length increased by 1.4- to11.0-fold over the control because the depression of radicle growth was more serious thanthat of plumule. Tissue electrolyte leakage was enhanced and subsequent greening did notoccur, then seedlings were dead in the following few days．MV treatment with leaf segments or roots of intact rice seedlings at 3-leaf stage caused membrane leakage， chlorophyll degradation，the decline of photosynthesis and the increase of dark respiration．The response of hybrid rice Youza to MV was slightly less susceptible than its parents． The results suggest that MV can enter the different organs of rice and display its toxicity．MV seems to induce not only the oxidative degradation of chlorophyll but also the limitation of chlorophyll formation．

Abstract:Calmodulin (CaM) content in protoplasts cultured with CaCl₂-or IAA (or 6-BA)-bearing medium raised after being incubated for 30 minutes. When treated with IAA (or6-BA)+CaCl₂, the CaM content decreased sharply, which just coincided with the increase of ⁴⁵Ca²⁺ accumulation and protoplast swelling as indicated in our previous studies. Eitherverapadril, LaCl₃, EGTA or W7 could increase the low CaM content to an approximate oreven higher value than that of control. A23187 and cations such as K⁺ and Zn²⁺,however, could reduce CaM level just as the influences of IAA or 6-BA with Ca²⁺, It was also consistent with the changes of ⁴⁵Ca²⁺ accumulation and protoplast volume．These results showed that CaM did act with Ca²⁺ during the modulation of protoplast swelling induced by IAA or 6-BA．

Abstract:Sequence comparison showed the high homology between rice repetitive DNAsequence pRRD9 and chloroplast gene psbA encoding QB protein. Southern hybridizationsof rice chloroplast and nuclear DNA with the two subcloned segments from pRRD9,pRRD9R and pRRD9L, revealed that psbA gene sequence was transferred from chloroplastto the nuclear genome in rice at a certain evolution stage. Significant differences occurredbetween the two segments in the evolution of rice variation. Southern analysis of wild and cultivated rices with the segments showed that the culfivated Asian rice had closer relatire of the wild rice with AA genome type．In addition， spedfic hybridization patterns were also detected in some wild rices．These findings suggest that pRRD9 may be a good molecular probe for the study of the evolution of rice ．

Abstract:The polyploid plants were obtained from the leaves of Sinningia Speciosa (Lodd.)Hiern treated by colchicine. Best result for inducing tetraploid was by adding colchicine20 mg L-1 intothe medium treated for one week rather than by colchicine soaking. Morpho-logical observation showed that the sterns and the leaves of tetraploid plants were respectivelythicker and lalger than the diploid ones. The chromosome number of tetraploid plants was 2n=4x=52, while that of diploid plants was 2n=26. Peroxidase isoenzyme analysis showed that the enzyme activities between the polyploid and the diploid plants were quite different．Two new bands were observed in the isoenzyme map of tetraploid plants．

Abstract:Tissue culture and rapid propagation of 9 cultivars of Dithenbachia were studied.The proliferation rates among the 9 varieties were quite different. Treatment with 3-5 mg L^-1 6-BA was favorable for adventitious shoot induction and plant proliferation. Treatment on 1/2 MS medium with 0.5 mg L^-1 NAA was best for rooting. A large scale production ofplantlets was established for 4 varieties, viz. D. maculata cv. Camilla, D. Maculata cv.Rudolph Roehrs, D. seguine cv. Wilson's Delight and D. amoena cv. Mars.

Abstract:Seven compounds have been isolated from the stems and leaves of Sibiraeaangustata (Rehd.) Hand-Mazz.. On the basis of spectral analyses (UV, IR, EI-MS, HNMR,13CNMR), the structures of these compounds were identified as betulinol (Ⅰ), ganodericacid Z(Ⅱ), ursolic acid (Ⅲ), 1-triacontanol (Ⅳ), tetracosanoic acid (Ⅴ), 10-nonacosanol(Ⅵ ) and 10-docosanol (Ⅶ ), respectively. The compounds Ⅰ, Ⅱ, Ⅳ, Ⅴ, Ⅵ, Ⅶ wereisolated from the plant for the first time.

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Abstract:Essential oil from the leaves of Sauropus androgynus (L.) Merr. was extracted bysteam distillation and analyzed by GCMS technique. The results show that the majorchendcal constituents of the essential oil are carvacrol methyl ether, thymol and butylatedhydroxytoluene.

Abstract:The studies of cavitation and embolization are the advanced subject of xylemwater transport problerns in woody plants. There have been published many papers, butdifferent viewpoints exist among different scholars. Based on the last 80 year' studies aroundthe world, the literature about xylem cavitation and embolization is summarized anddiscussed in this paper, which include the parts of the discovery, measuring methods,induced factors, formation mechanism, the relationship between hydraulic architecture and xylem embolism，etc．The hot position of this field is also pointed in order to draw more interests in the study．