Abstract:Based on the data investigated from l988 to 1998 for air and soil temperature and moisture in a 15-year-old artificial forest of A cacia mangium in Guangdong, China，the temporal and spatial dynamics of the forest was analyzed． The results showed that even 7-year-old A．mangium forest was able to have function of regulating air and soil temperatures, to delay temperature variation, and to increase moisture in the forest Mean air temperature within 11 years inside forest was 21.7℃ which was 1ower than that outside forest by O.5℃．Mean soil temperature at 0—20cm depths under forest was 21.3℃ which was lower than that outside forest by 2℃, the effeet of forest on lowering temperature was more obvious in wet season than in dry season Air temperature inside forest decreased vertically with height increase at daytime，but to the contrary at night. The differences in temperature at the four vertical layers (forest height at 0.5, 2, 7 and 16 m) were more distinctive in dry season than in wet season. Air relative humidity inside forest averaged 82％ which was higher than that outside forest by 4％.

Abstract:Based on the data of Pinus massoniana tree ring in Dinghushan Nature Reserve，Guangdong Province， the productivity of Pinus massoniana population from 1953 to 1991 was obtained using allometric method．The correlation between the changes in local temperature and the productivity of the population was analyzed by MICROSOFT EXCEL program utiIizing meteorological data． The result showed that the productivity increascd by 3.31 t hm^-2a^-1 with air temperature increase of every 0.6℃.

Abstract:Grey correlation analysis was used to study the efects of vegetation status on species diversty of tree seedlings in a subtropical evergreen forest in Dujiangyan (Sichuan Province)．Twenty-two plots with 5 m×5 m each in a sample site of 10 m×55 m were investigated． Data obtained included plant species，number of individuals，plant height，diameter at breast height，and canopy coverage in tree layer；plant species density and coverage in shrub and herb layers；and species, individuals and plant age of tree seedlings above 13 m．Species abundance index (S)，Simpson index (D)，Shannon-Wiener index (H), and Pielou evenness index (E) were used in α-diversity analysis. The results indicate that the parameters of vegetation status affecting species diversib, of tree seedlings are greater in D in herb layer, and H and coverage in shrub layers；but less in H in shrub layer an dcoverage in herb layer．The effect of vegetation status on the four species-diversty indexes are in the order Pielou evenness index>Shannon-Wiener index>species abundance index>Simpson index．

Abstract:Data for breath height diameter, stand height，number of individuals，standing biomass plant age we measured from 256 temporary plots and 24 permanent undisturbed plots of Pinus massoniana plantations on hilly land of north Fujian Each plot covered an area of 0.06-0.08 hm^-2 Permanent plots were investigated for five times in the study. The original stand density was 3 000-4 500 trees aged from 8 to 34 with site index of 16 m．Self-thimting mode1 was based on the model for biomass of population growth, ie. dB/dt=rB[1-(B/K)^θ] and by law of 3／2 self-thinning，from which the following model was dcduced：N＝｛[A(1+ce^-ft)^b]^-p-[A(1+ce^-ft₀)^b]^-p+N₀^-p｝^-1/p. This modeI can well imitate the actual population density observed，suggesting that it is a more accurate and applicable model．

Abstract:Embryological features of threatened Orchidamha chinersis were studied with the help of a Ileitz microscope．Living specimens were collected from the South China Botanic Garden at Guangzhou．Special emphasis is given to the 0vule development, megasporogenesis, egagametogenesis and the development of endosperm The ovules of 0.chinensis are anatropous, crassinucellate and bitegmic．Micropyle is formed by inner and outer integuments Aril originates from top end of outer integumem．The ovule has a layer of parietal cells at the sporogcnous stage Sporogenous cell develops into a megaspore mother cell, and then divides meiotieally into a linear megaspore tetrad mad sometimes triad．Chalazal megaspore is functional. The development of the embryo sac is of Polygonum type．Chalazal end of mature embryo sac is narrow and elongated．The ovule has epistase and hypostase structures．Antipodal cells are longevous. The type of vascular bundle in the ovule belongs to postchalazal multibundles．The development of endosperm is of nuclear type．Plumule and radicle are not differentiated when the seeds fall. We recognize that the elongated part of the ovary, in Lowiaeeae is functional for continuous dovelopment of pollen．Main characteristic differences among 8 families in Zingiberales，and the reproductive biology of Lowiaceae are discussed．

Abstract:Flower location． sex ratio and numerical variation of the flower parts of Woonyoungia septentrionslis (Dandy) Law，an endemic species in China，were investigated by random sampling trees from natural population of Woonyougia septentrionalis in Mulun Village，Huanjiang County (Guangxi Province). Although most of the flowers (90％) were terminal as previously described，a small fraction (10％) were found to be axillary，which was not recorded previously．The ratio of male to female individuals was 1.2 1:1 Statistic results from 600 flowers iD 20 individuals from introduced trees in South China Botanica1 Garden and from natural population iD Mulun show that the number of flower parts， except the number of thecae per stamen an d the number of ovules per carpel，is variable．The variations are：2—6 tepals in one or two whorls．81—1 52 stam ens in male flowers，two whorls oftepals， 2—4 in the outer whor1．5—13 in the inner．and 3-8 carpels in fema1 flowers．Two thecae in each stam en， an d two ovules iD each carpel are the only stable characters．Great vailation in flora1 characters indicates that this species possesses high genetic diversib'．The phyIogenetic significance of co-occurrence of axillaD,and term inal fowers．the heterobathmy of flora1 characters，an d the tenability of the genus m Jonyoung~a are~iscussed

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Abstract:Rare and endangered plants in Shenzhen， Guangdong Province， were surveyed， which comprise of 19 species and onevariety belonging to 18 generain 17 families．The plants names including degree of threat, grade of protection and the distribution in Shenzhen are tabulated．Among these plants， vulnerable Alsophila spinutosa and endangered Cycas fairylakea are of the state grade of the state protection. A list with 44 taxa that are suggested to be protected is given．

Abstract:The relationships among cultivars of Pomelo [Citrus max ima (Burm.) Merr.] and two related species, Grapefruit (C.× paradisi Macfad) and Honghe Papeda (C. hongheensi．Y．M．et al.)，were investigated from 79 samples, which were probed using RAPD technique and statistical anaiysis． Twenty-two random 10-base primers were screened for the study． They produced 164 RAPD marker bands among 79 accessions, in which 134 RAPD bands were polymorphic．The rate of polymorphic RAPD bands was 81.71％．Using NTSYS-program and the method of UPGMA, Jaccard genetic similarity coefficient among accessions was calculated, and the dendrograms were constructed． The results show that three species correspond with three clusters of UPGMA dendrogram, supporting the species stallls of pomelo．Some cultivar-specific RAPD markers are found as important markers for pomelo identification．

Abstract:Three bar-transgenic rices，Bengal Hu-10，Cypress PB-6，and Gulfmont as male parents，were crossed with 6 male sterile lines：Zhenshan 97A, Bo A，Pei-ai 64S，Nan xiang 95S，Xi 217S and GD 1-S. Eight restorers emasculated were crossed with the three herbicide-resistant sources．Forty-eight F₁ hybrids were obtained totally The results indicated that heterosis in these F₁ hybrids were not obvious By transferring herbicide (Liberty)-resistant bar gene into conventiona1 restorer 1ines, 3 restorer 1ines (Minghui 63-B，Ce 64一B．and Teqing-B)were developed via crossing，and 5 resistant combinations，i.e Zhenshan 97A／Minghui 63-B (B₂F₁-B), Zhenshan 97A／Ce64一B(B₂F₂-G)．Zhenshan 97A／Ce 64-B(B₃F₁-C)，Pei-ai 64S／Teqing-B(B₁F₂-C)．and Pei-ai 64S／Teqing-B(B₂F₁-B)，had been bred，which retained the same yielding level oftheir original combinations．The problems ofheterosis application，and the prospect of bar-transgenic rice parents in breeding for heterosis are discussed.

Abstract:An investigation on some growth characteristics of three varieties of sweet-glutinous maize (Zea mays L)(cv．Kandy Corn，Early Sunglow，and Peaches＆ Cream) introduced from U.S.A. was made in cropping season in 1999 at the experiment field of South China Institute of Botany in Guangzhou. All the varieties observed could well adapt to the climate conditions with high temperature and high moisture in Guangzhou，and could resist to lodging．No diseases and pests were found．Of the 3 varieties Early Sunglow had growth-duration of 76 days from sowing to harvesting，which was 18 days earlier than supersweet 9501 (Control), but the yield was lower by 21.2％ than the control；The duration from sowing to harvesting for Kandy Corn and Peaches ＆ Cream were two weeks shotter than that for control, but the fresh ear yield was respectively lower by 15.9％ and 17.9％ than control. It is suggested that the three varieties would be elite germplasm for maize breeding in Guangdong or South China．

Abstract:The seeds of lndica rice (Oryza sativa) variety FAZ一5 were treated with ethyl methane sutfonate (EMS) for mutation breeding．A reduced till mutant (ret5-5)，which exhibited no tiller, was obtained from M₂ population The selfed progenies M₃, M₄ and M₅ showed 0-2 tillers．while its parents， FAZ一5，had average 8.2 or more tillers in the corresponding period The mutant ret5-5 after being crossed with FAZ-5 indicates that it is a recessive mutant and more than oue gene were mutated after the EMS treatment．

Abstract:Seed development, heat stable proteins, the accumulation ofsugars， and antioxidative systems， which associate with seed desiccation lolerance，are reviewed The storage of recalcitrant seeds is difficult due to their sensitivity, to desiccation. The possible ways to increase desiccation tolerance for recalcitrant seeds are suggested．

Abstract:Canopy gap，mainly caused by small scale of disturbance，plays all important role in forest regeneration cycle. Gaps increase species diversity of forest communities through the heterogeneity of the habitat, which effect species composition，forest structure，dynamics，and the biodiversity in forests. In this paper，a review of the study on gap characteristics， gap-phase regeneration, dynamic models in gap researches, as well as gap theotry is presented.