Abstract:The activity of ACC synthase(ACS, EC 4.4.1.14) from etiolated mungbean seedlings was elevatedobviously in treatment for 20 min with 0.5, 5 or 50 mmol/L of sodium dithionite (Na₂S₂O₄) which is generally used as an exogenous generator of superoxide radical (O₂^-·). Superoxide dismutase (SOD) or 1,4-diazabicycol (2,2,2) octane (DABCO), a special scavenger of O₂^-·, could reduce the increase of ACC synthase activity induced by Na₂S₂O₄, showing the promotion role of superoxide radical on the activity of ACC synthase. However，the activity of ACC synthase decreased as the treatm ent time extended．The activity of ACC synthase was even lower than the control when treated for 60 min with 5 or 50 mmol／L of Na₂S₂O₄．The decline of activity of ACC synthase could be inhibited by adding SOD or DABCO．These results showed the dual-efect of superoxide radical on the activity of ACC synthase．The further studies indicated that Krn of ACC synthase，which substrate is S-adenosylmethionine (SAM)，decreased in treatment for 20 min with exogenous generator of superoxide radica1．However，in the treatment for 60 min with exogenous O₂^-·，the value of Km of ACC synthase increased obviously．The results showed that superoxide radical could change the properties of the ACC synthase，i.e.，decreased its Km value，increased the affinity to SAM，and thus，to alter the activity of ACC synthase．This might be the mechanism of the dual effect of superoxide radical on the activity of ACC synthase.

Abstract:Polyethylene glycol (PEG) induced osmotic stress increased the contents of putrescine (Put), spermidine (Spd) and spermine (Spm) in seedlings of drought-resistant wheat strains Zhou and the content of Put in seedlings of drought-sensitive wheat Wen 6. Exogenous Spd (1 mmol/L) obviously increased the content of Spd in seedlings of Wen 6 and its resistance to water stress increased to some extent. Methylglyoxyl-bis (guanylhydrazone) (MGBG,1 mmol/L), an inhibitor of biosynthesis of Spd and Spm, increased the increased the content ofPut in wheat seedlings of Zhou 12 under water stress，but decreased the contents ofSpd and Spm as well as its drought resistance.

Abstract:Effects of ethephon, 1-aminocyclopropane-1-carboxylic acid (ACC), aminioxyacetic acid (AOA) and AgNO₃ on adventitious rooting in mung bean hypocotyl cuttings were studied. Results indicated that ethephon and ACC promoted adventitious root formation in mung bean hypocotyl cuttings, the optimal concentrations being 50 μmol/L and 10 μmol/L respectively, whereas AOA and AgNO₃ significantly inhibited adventitious rooting, and the effect of which were dose-dependent. The promoting effect of ACC and the inhibitory effect of AOA on the cutings excised after 24 hours were sensitive．The rooting efects were best in treatment with 10 μmol/L ACC for 0-6 hours an d 18-24 hours， and in treatment with 50 μmol/L ethephon for 0-2 hours and 22-24 hours．It is concluded that the promoting efects of ethephon and ACC on adventitious rooting were at induction stage and late initial stage．

Abstract:Studies on the growth and photosynthetic characteristics in Guzmania‘Danis’ were conducted in plastic greenhouse with top covered by shading net under elevated CO₂ (1 000±100 μmol mol_-1) and ambient CO₂(360±30 μmol mol_-1) conditions. The results showed that the plant height, leaf area, fresh and dry weightsof plants under elevated CO₂ were 120.19%, 119.22%, 177.91% and 161.04% of those under ambient CO₂, respec-tively, as determined after 90 days of experiment. Under elevated CO₂ condition, the net photosynthetic rate increased to l36％-259％ and chlorophyll content decreased to 33.9l％ in comparison with those under ambient CO₂ during the experiments． Elevated CO₂ stimulated the accumulation of soluble sugar an d starch， but declined the activity of glycolate oxidase in leaves，however，the activity of RuBPCase increased only slightly.

Abstract:Pollen morphology of 15 species of genus Calamus (Palmae) from China were studied by means of light microscopy and scanning electronic microscopy. The structures of pollen grains in observed species are of sametype. The apertures is dicolpate, the tectum of exine is reticulate (C. macrorrhynchus) or perforate (C. rhabdocladus).It is the first time that perforate, verrucose (C. pulchellus) and rugulose (C. flagellum) were observed on the exine textum of the genus Calamus. The size, shape and exine ornamentation，verrucose，exine thickness，and the size of lumina in pollen grains are of great significance in the systematics at species level of the genus Calamus．

Abstract:Japonica rice cultivar, Taichung 65, and its seven F₁ pollen sterility near isogenic lines were employed to study the impact of pollen sterility locus on anther dehiscence in hybrid F₁ using the anther dehiscence index asindicator. The results showed that the anther dehiscence trait was controlled by genic interaction of pollen sterility loci. Allelic interaction at different pollen sterility loci resulted in different degree of anther indehiscence in hybrid F₁. Allelic interaction at S-b locus resulted in part of anther indehiscence in hybrid F₁．Genic interaction between pollen sterility loci obviously decreased the anther dehiscent ability．The more heterozygous pollen sterility loci the hybrid F₁ had，the worse anther dehiscence the hybrid F₁ was．The hybrid of T65×TISL245 had three heterozygous pollen sterility loci，its anther dehiscence index was only 2.27 and the anther dehiscence ability was worst．The main causes resulting in poor anther dehiscence in hybrid F₁ were different with the kind and the number of heterozygous pollen sterility loci．The anther dehiscence markedly decreased the total number of pollen grains and the number of pollen grains germinated on stigma. The positive correlation betw een anther dehiscence indexand spikelet fertility was extremely significant.

Abstract:Based on shoot-tip multiplication technique, the application of in vitro selection of black peppersomaclones resistant to foot rot disease caused by fungus Phytophthora capsici was carried out using a large-leaf variety Daye (Lampong Type) which is widely cultivated in Hainan but highly susceptible to P. capsici as explant resources. The results demonstrated that sterilization methods significantly influenced on the toxicity of the culture filtrate of P. capsici. The fungal filtrate toxicity could be maintained using filtrate sterilization by addition of the fungal filtrate into selective medium instead of autoclave sterilization． The survival rate of shoot tips and multiple shoots decreased with the increasing concentrations of the fungal culture filtrate． Some cultures blackened and died finally, and some formed calli or remained dormant．After 2 subcultures onto the same selective medium， microshoots were rooted in vitro and tran sferred to the greenhouse conditions for screening the resistance to fungus P. capsici．The plants exhibited no external symptoms of the disease during three successive times of resistance assay once two weeks were considered to be resistant． As the concentrations of fungal culture filtrate increased，the total number of regenerated plants obtained declined but the frequencies of plants resistant to capsici increased．1(1.54％)，4(20.OO％) and 3(42.86％) disease resistant somaclonal variants were obtained at concentration of 25％ ，50％ and 75％ fungal culture filtrate as selective agents， respectively，with the total number of 8 plants resistant to P. capsici.

Abstract:Six sesquiterpene lactones were isolated from the whole plant of Wedelia trilobata (Compositae). On the basis of spectral data, the structures of these constituents were identified as trilobolide-6-O-isobutyrate (1), 1β-acetoxy - 4α, 9α-dihydroxy - 6β- isobutyroxyprostatolide (2), 1β, 9α- diacetoxy- 4α- hydroxy - 6β- isobuty-roxyprostatolide (3a), 1β, 9α-diacetoxy- 4α-hydroxy- 6β-methacryloxyprostatolide (3b), 1β, 4α-di hydroxy - 9α-tigloyloxy-6β-methylpropanoylprostatolide (4a), and 9α-angeloyloxy-1β，4α-dihydroxy-6β-methylpropanoyl-prostatolide(4b)．All compounds except 1 and 3a were isolated from this plant for the first time．Compounds 1，2，a mixture of 3a and 3b， and a mixture of 4a and 4b exhibited potent growth inhibitory effect on the seedlings of radish，cabbage，and tomato in seed germination and seedling growth inhibition test．The mixture of 4a and 4b showed toxicity to brine shrimp in lethality test.

Abstract:Aroma extract from the fruits of Artocarpus heterophyllus was obtained by solvent extraction. Eighty-two compounds in the extract were identified by means of GC-MS technique. The content of these compounds makes up 94.66 % of the total components, which include fatty acids, esters, alcohols, alkoxy alkanes and ketones. The main constituents are linoleic acid (24.10 %), palmitic acid (15.72 %) and oleic acid (6.16 %).

Abstract:Shimentai Nature Reserve is situated in the center of north Guangdong, 24°17'49"- 24°31'02"N, 113°01'11"- 113°46'22"E. It occupies about 82 260 hectares, and is the largest nature reserve in Guangdong. According to our field surveys and studies in the past three years, 158 species of mosses in 89 genera and 33 families are recognized from Shimentai Nature Reserve. Among them, 3 genera (Eccremidium, Phyllodon, and Stereodontopsis)and 23 species are newly recorded for Guangdong.

Abstract:A floristic survey was made of a Tsuga longibracteata community in Tianbaoyan National NatureReserve in Fujian Province. There are 140 species of vascular plants belonging to 49 families and 86 genera in the investigated quadrats with a total area of 3 600 m2 in the community, in which pteridophytes comprise 7 families, 7 genera and 9 species, gymnosperms 2 families, 4 genera and 4 species, and angiosperms 40 families, 75 genera and 127 species. The floristic elements at the family and genus levels are mainly pantropical with a certain proportion of temperate elements， whereas at the species level， species endemic to China and species of East Asia are the dominants with larger proportion of temperate elements and certain proportion tropical elements． Th e longibracteata community containing considerable amount of primitive taxa is considered to be endangered． The areal types of vascular plants in the community at family，genus and species levels are tabulated.

Abstract:Pollen of Torenia fournieri is two-celled and the division of generative cell occurs in the pollen tube. In vivo - in vitro technique was applied to get isolated sperm cells. After growing in vivo for 5 h, the pollinated style was cut and transferred into a medium containing 5% (w/v) sucrose, 0.01% (w/v) H3BO3, 0.01% (w/v) CaCl2, 0.01% (w/v) KH2PO4, at pH 5.0. Numerous pollen tubes emerged from the cut end of the style after culture for 2-3 h. When the pollen tubes were transferred to a broken solution containing 5％ mannito1, some pollen tubes broke and the tube contents including two sperm cells were released in the broken solution．The two sperm cells of Torenia fournieri are dimorphism：one is big and the other small．The bigger one (Svn) associates with vegetative nucleus and the small one (Sua) associates with the bigger one．Two sperm cells can be divided into two individual groups using a micromanipulator．These tw o dimorphic sperm cells could provide male gametophytic cells for further in vitro studies and various biotechnological experiments，such as preferential fertilization and gametic recognition in higher plant.

Abstract:Seed surface is unclearly observed of contaminated small seeds collected from herbarium specimens.After being soaked in low concentration of commercial detergent (0.001%), shaken in the ultrasonic wave bath(33 kHz, 50W), and rinsed in series content of ethanol with weak shaking in ultrasonic wave bath, the treated seed surface becomes more clear than untreated ones under SEM. This method is easy to operate and obviouslyeffective.

Abstract:Experiments were conducted to test the effects of pure O₂ on browning of litchi (Litchi chinensis Sonn. cv. Huaizhi) fruit in relation to the changes in ultrastructure of peel tissue. Litchi fruits were kept in air or pure O₂ for 6 days at 28℃. Browning index and relative leakage rate were determined, and the changes in cellular ultrastructure was observed. Application of pure O₂ significantly prevented browning and delayed the increase of membrane permeability in litchi fruit pericarp. Exposure of litchi fruits to pure 0₂ resulted in a delayed breakdown of cytoplasm and valdous organelles， which might account for the maintenance of cell membrane integrity． It is suggested that the partial protection from breakdown of cellar integrity of litchi fruits by pure O₂ treatment could reducebrowning.

Abstract:Six formulations containing cane sugar, sodium benzoate, aluminium sulphate, paclobutrazol, 8-hydroxy quinoline, vitamin C, tartaric acid, potassium permanganate, silver nitrate and aspirin, with different concentrations and various combinations, were used as preservatives to observe the changes in morphology and in starch grainsin cells of cut flowers of carnation. After treatments with preservative, the flowers enlarged and bright-colored.The contraction in cell walls of stems, leaves, petals, ovaries and ovules was delayed. The duration of starch grains in cells was prolonged．Preservative solution with sodium benzoate was better than that with silver nitrate．

Abstract:

Abstract:Seven species, Selaginella scabrifolia, Diplopterygium blotianum, Aristolochia hainanensis, Eurya quinquelocularis, Trema nitida, Rhododendron hainanense, and Pertya cordifolia, are reported as new records from Guangdong Province.

Abstract:Gynogenic haploids through unfertilized ovules and ovaries have been reported from 21 species in 9 families since 1976. This review includes the following subjects: induction frequency of haploids depend on genotypes, developmental stage of explants, temperature pretreatment of the explants, medium composition and the conditions of cultivation. Embryological studies reveal that megaspore and such cells as egg, synergid and antipodals in mature embryo sac initiate the division of forming haploid plants through embryogenesis or callus formation．This technique provides an optimal approach to haploid breeding．

Abstract:The role of virus movement protein in the spread of infection in plants is reviewed. The subjectsinclude: movement protein-nucleic acid complex mediates viral cell-to-cell movement; the roles of cellularorganelles or cellular factors on viral spread, including endoplasmic reticulum, cytoskeleton, pectin methylesterase, inclusion bodies, and β-1, 3-glucanase; and regulation of the activity of movement protein.