Abstract:Relatedness of importance values of dominant populations to the ecologicalfactors in secondary succession of forest communities in Heishiding NatureReserve, Guangdong Province, was analyzed by using relatedness degree of the gray systemtheory. The results showed that pioneer species, Pinus massoniana, Cunninghamia lanceolataand Schima superba, were mainly affected by transmittance in the communities. Otherheliophytes such as Schefflera octophylla, Meliosma fordii, Diospyros morrisiana and Symplocos adenophylla were less affected by the environmental factors The mesophytes， Artocarpus styracifolius，Lithocarpus fohangwa Machilus breviflora，Lindera chunii and Cryptocarya concinna，were mainly afected by the richness of species and density of the communities， while mesophytes such as lxonanthes chinensis and Altingia chinensis were mainly affected by transmittance in the communities．The influences of the environmenta1 factors or fifteen dominant populations in descending order were transmittance in communities，richness of species，density of communities and conditions of soil. Comprehensive influence of all environmental factors appeared greatly on the mesophytes as compared to other species．

Abstract:The effects of five different ecosystems on surface runoff were studied through"watershed experiments" during 1993 to 1997 in Heshan Hilly Land Experiment Station.The results showed that the surface runoff coefficients of five ecosystems, viz. Acaciamangium forest, orchard, leguminous mixed forest, grassland, and forest-orchard-nurserysystem, were 2.3%, 6.97%, 13.30%, 17.90% and 22.16%, respectively, while thevariation rate difference of runoff modulus were in the order of A. mangium forest < leguminous mixed forest < forest-orchard—nursery system < grassland < orchard, being O.46，O.57，0.63，O.65 and 1.68 respectively The results showed that A .angium forest and legum inous mixed forest have better hydrological function on water conservation and adjustment than the others. Surface runoff coeffcients were different among the seasons showing that wet season > annual > dry season, but the seasonal change in variation rate diference of runoff modulus was in the order of dry season > annual > wet season. Between surface runoff （R）and precipitation (P)，there was a regressive relation equation，R=aP²+bP+c，and surface runoff had rio significant relationship with the rainfall intensity, and the surface runoff was often provided by some heavy rains The rainfall causing surface runof in A．mangium forest，orchard，leguminous mixed forest forest-orchard-nursery system and grassland were 15.9，13.28．8.1，6.71 and 5.21 mm，respectively The runof occurence and the flood peak was delayed by the five ecosystems for 10 to 30 minutes，and the maximum appeared in A． mangium forest．Some flows in hydrological function of orchard and forest-orchard-nursery system are discussed.

Abstract:Based on the measurement of biomass and the rate of its increase, caloric value ofrespective plant organs, energy of standing crop, annual net energy fixation and energyconversion efficiency in Cyclobalanopsis elevaticostata community in subtropical zone at950 m altitude in Fujian Province were determined in 1996. The results showed that thecaloric value of the bark was the highest and the microroot being the lowest among dryweight of plant organs in the community. Total energy of standing crop in the community was 852 058 kJ m^-2, of which the aboveground part comprising 87.O1％, and the underground part 12.99％. Yearly net energy fixation was 28 273 kJ mkJ m^-2， and energy conversion efficiency was 1.35％ for the community．

Abstract:Natural Pinus massoniana stand in Wanmulin Nature Reserve of Fujian is amixed forest dominated by Pinus massoniana and associated with broad-leaved tree species.The species diversity of the stand is similar to that of the natural broad-leaved standsaround. The stand volume is 984.2 m³ hm^{-2 which is rarely seen as a typical high-yieldnatural Pinus massoniana stand.}

Abstract:The flora of Hong Kong was surveyed by the first auther during March 1996 toJune 1998 according to the Project of investigation on the Biodiversity of Hong Kong.More than 3 500 specimens were collected, of which some 100 species were new records toHong Kong. In this paper the history of floristic researches, the vegetation, the floristiccomponents, endemism, the rare and endangered species as well as a comparison of theHong Kong flora to the neibouring regions are presented. Hong Kong is rich in plant diversity， so far a total of 2 145 vascular species in 973 genera of 224 families，including 216 species in 97 genera of 45 families of ferns have been recorded, of which 16 species are listed to be protected by China government and 166 species by government of the Hong Kong. Special Administrative Region．The most species-rich families are Gramineae，Orchidaceae，Papilionaceae, Cyperaceae，Compositae Rubiaceae， Euphorbiaceae， Lauraceae， Fagaceae, Moraceae，Theaceae and Myrsinaceae the latter seven being dominants in forests The species-rich tree genera with more than 10 species are Ficus, Lithocarpus，Ilex，Machifus，Sympfocos，Castanopsis，Cyctobatanopsis and Camellia，all of which are also dominants and are of tropical and subtropical elements．As a part of Guangdong flora，the flora of Hong Kong is closely related to that of Hainan and Indo-China，and they share the same origin.

Abstract:Total DNA was extracted from the leaves of generated tomato plants that werescreened and non-screened with fusaric acid, and was used to make the optimization forRAPD analysis. Four of the 60 random primers were adapted for the identification ofsomaclonal variation. This kind of method is not only simple, rapid, but also accurate.Furthermore, because the quantity of the DNA template is less, it is not influential in thegrowth of the tested plants. Therefore, this method can help us to pick out the plants that are physiologica11y tolerant， whereas mutant plants are reserved.

Abstract:The impacts of the concentrations of template DNA, primer, magnesium, dNTPand Taq DNA polymerase on RAPD amplification for Camellia were tested by means ofladder analysis. The results showed that RAPD band patterns were changed observablywith the variation of concentrations of template DNA or primer or Taq DNA polymerase,and there was a positive interrelation between the both within a limited range, but littleimpact was generated by the concentrations of 1.0-4.0 mmol/L MgCl₂ or 100-400 μmol/LdNTP on RAPD band patterns The optimal amplification conditions for Camellia were chosen as follows：4 ng template DNA／μl reaction volume，15 ng primer／20 μl reaction volume，2.0 mmol／L MgCl₂，200／μmol／L dNTP．1 U Taq DNA polymerse／20 μl reaction volume.

Abstract:The superoxide radical (O₂^-.) formation rates in the young panicles and anthers ofcytoplasmic male sterile (CMS) rice Zhenshan 97A (97A) and its maintainer Zhenshan 97B(97B) were inhibited by KCN, and accelerated by salicylhydroxamic acid (SHAM), but thepercentage of O₂^-. formation inhibited by KCN or accelerated by SHAM in sterile rice 97Awas more than that in fertile rice 97B. The malondialdehyde (MDA) content in both of 97A and 97B increased after KCN or SHAM treatment, but the great change of MDA was found in 97B treated by KCN or in 97A treated by SHAM. Superoxide dismutase (SOD) activity was inhibited by KCN, but was not affected by SHAM. The respiratory rates of 97A or 97B decreased after H₂O₂＋FeSO₄ treatment H₂O₂ while it did not change by treatment alone.

Abstract:Effects of different extents of oxidative stress caused by 10 μmol/L H₂O₂ or μmol/L methyl viologen (MV) on cold tolerance of rice seedlings were studied. Theresults showed that mild oxidative stress (10 μmol/L H₂O₂ or 10 μmol/L MV for 4 h)could induce cold tolerance, while severe oxidative stress might aggravated chilling injuryon rice seedlings. The antioxidatase (POX, SOD, CAT andf APX) activities in leaves fromvarious pretreated seedlings were all increased. After chilling stress, the changes in antioxidatase activities．electrolyte leakage and MDA content among different pretreated seedlings were difierent Mlid oxidative stress could sustain high IeveI of antioxidatase activities，reduce the increase of membrane lipid peroxidation and cellular electrolyte leakage induced by chilling stress； but contrary effect was observed by severe oxidative pretreatment. It is suggested that the mechanism of rice seedlings responsing to oxidative stress (cellular oxidative stress response) might be the important regulatory mechanism for rice seedlings during chilling stress or cold tolerance.

Abstract:The ovary locule of Orchidantha chinensis is closed at the top and extendsupwards to form prolongation that is solid and penetrated by the stylar canals andgynopleural enctary ducts. One central nectary duct and three lateral nectary ducts can berecognized, and the central one is situated in the fused region of the three carpels, whilethe lateral ones are between that of two carpels. The central duct arises at the lower part oflocular region of the ovary, extending upwards and closing at the end of the narrow part of the prolongation，while the three Iateral ducts occur at nearly the middle of the locular region and exit beside the base of the style． Vascular bundles of six stamens， three accompanying bundles of the dorsals and three parietal bundles，exist in locular region and prolongation，while the adaxial parietal bundle fuses with the vascular system which will enter labellum in the uppermost part of the prolongation As a result the labellum is a double structure and the flower possesses only five stamens The phylogenetic position of Lowiaceae is also discussed.

Abstract:Isoenzyme and SDS-PAGE techniques were used to analyze 11 cultivars of genusCymbidium. Among 24 bands of esterase and cytochrome oxidase, 23 were polymorphic,and 25 of 30 bands produced in SDS-PAGE were polymorphic. Based on the clusteranalysis of these markers, biochemical results were consistent with those of traditionaltaxonomic study, except that the systematic status for several Cymbidium cultivars weredifferent from the mophological classification.

Abstract:The meteorological factors in two mangrove communities (Rhizophora stylosacommunity and Bruguiera gymnorrhiza community) and open area were compared in July of1997 in Yingluo bay of Guangxi Province. The results showed that the daily mean lightintensity of Rhizophora stylosa and Braruiera gymnorrhra communities were lower by 81.9%and 49.8% respectively as compared to that of the open area. The mean soil temperatureand mean wind speed were lower by 1.8℃ and 2.3℃, and by 64.7% and 67.7%,respectively. Daily change in air temperature and relative humidity in Rhizophora stylosa community were larger than those in Braruiera mnorrhiza community and open area．

Abstract:In recent years, people have experienced great disasters which result fromdisruption of forests. Close attention is paid increasingly to hydrological function of theforests. In this paper, a brief history of researches in this field and the prospects concernedare reviewed. There are two periods in the researches: forest influence and forest-ecosystemhydrology. The effects of forests on rainfall, regulation of hydrological process, hydrologyof soil water and underground water, and ecological benefits of forest hydrology are presented. The author suggests that three aspects need to be emphasized．viz，the coupling research on forest pattern， and hydrological scale and process； research on regional characteristics；and the structure of water inflow and outlet in forest ecosystem．