Abstract:In this paper an overview is given of the flora of China which comprises some 30 560 species in 3 150 genera of 343 fairlies of seed plants, being 13%, 25% and 61 % of the world 's flora, respectively. Woody plants of China consist of some 2 000 species in 1 200 genera of 187 families, and shrubs comprise 6000 species, herbaceous species are included in 156 families. All of them are mostly the forest components except for hydrophyte with 26 families and some alpine plants. The distribution patterns of floristic elements is tabulated according to Wu Cheng-yih's "The Areal Types and Subtypes of Chinese Genera of Seed Plants" with some variation. The distribution of the families are classified in 14 areal types with 17 subtypes, in which tropical families, exclusive of cosmopolitan one, amount to 190, being 66.4% of total fairlies in China. The distribution of genera lies in the regions of 15 areal types with 33 subtypes, in which 1 542 genera (notincluding 106 cosmopolitan genera) are tropical, being 50.7% of total genera in China. The ratio of tropical genera to temperate genera is about half-and-half. Thus, it could be recognized that the forest flora of China is of subtropical nature, an intermediate flora between tropic and temperate floras. China has a large number of endemic genera and species amounting to 251 and 17300, respectively, which represent 8.2% and 60% of the total genera and species in China, respectively. Floristic differences from north to south,and from east to west of China are obvious. The flora of Heduan Mountain region is extremely diverse, which possesses some 7954 species in 1 325 genera of 226 fairlies, being 26%, 42.l% and 65.9%, respectively, of the total taxa in China, and having a large number of endemic taxa. The flora in central region of China is a typical subtropical flora due to enriched elements of East Asia and a large number of endearic plants amounting to about 4035 species. Flora in the south part of China is tropical flora in nature as it is bounded by the north part of Tropical Asia. In arid areas of North-west China, however,forest flora occurs only by rivers, comprising Ancient-Mediterranean elements and having very limited amount of species.

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Abstract:Three taxa of Euphorbiaceae from southern China are reported. Crotondinghuensis H. S. Kin is a new species. Croton guizhouensis H. S. Kin is a new name forCroton urticifolius Y. T. Chang & Q. H. Chen (1983) which is a later homonym ofC urticifolius Lain. (1786). Croton xiaopadou (Y. T. Chang & S. Z. Huang) H. S. Kin is anew combination.

Abstract:According to the published sequences, PCR primers of lundnocyclopropane-1-lcarboxylate (ACS) and l-aminocyclopropane-lcarboxylate oxidase (ACO) gene of tomato amplification were designed. Fragments of ACS and ACO gene were generated. The products of PCR fragments and T-vector ligation were transformed into E. colt (DH5a).The recombinants were selected by blue-white colony screening and restriction analysis.After partial sequencing and Southern hybridization, the fragments and stringed products o f two genes were subcloned into plant gene expression vector pBllZI in antisense orientation. The antisense vectors were transformed into Agrobaterium tumefaciens LBA4404 by freeze-thaw method. Fourteendayxild cotyledon pieces were infected with Agrobacterium,and transformants were selected with 75 ig nil-l kanamycin. Southern blotting with 0.gkb fragments of ACS gene as probe provided that two positively transgenic plantletS were obtained.

Abstract:The generation of .OH from Cu,Znroontaining superoxide dismutase (CuZn-SOD) reacting with H₂O₂ was studied by using deoxyribose degradation method in which deoxyribose reacts with. OH to release TBA-reactive compounds. Cu, ZnSOD could be inactivated by H₂O₂, during which. OH was produced. Formate and benzoate,scavengers of. OH, could partially protect Cu,Zn-SOD against inaCtivation by H₂O₂, and could inhibit the generation of. OH from Cu, Zn-SOD reacting with H₂O₂. Heat inactivated Cu,Zn-SOD could also react with H₂O₂ to generate. OH, and it was more effective in generating .OH than the active Cu,Zn-SOD. Apoprotein of Cu,ZnSOD did not catalyze .OH generation from H₂O₂. Zn²⁺ could hardly react with H₂O₂ to form 'OH, whereas Cu²⁺ was highly effective in generating. OH through Fenton reaction. These observations suggest that the generation of. OH from Cu,Zn-SOD reacting with Hood is due to the Fenton reaction between H₂O₂, and Cu²⁺ in the active center of Cu,Zn-SOD.

Abstract:An unicellular green alga DUnaliella salina 1009 was used as a plant cell model to study the effects of SO^2-₃ and HCO^-₃ on chlorophyll fluorescence under high light intensity (1000 μmol m^-2s^-1) with measurements by modulation pulse fluorometer (PAM). The initial fluorescence (Fo) was induced by a weak measuring light, and the actinic light was at 150 μmol m^-2s^-11, while maximum fluorescence (Fm) was produced under a strong saturated pulse light (6000 μmol m^-2s^-1). The results indicated that the photosynthesis of D. salina 1009 was stimulated by low concentration of SO^2-₃ (1 mmol/L) under high light intensity (1000 μmol m^-2s^-1) for 1 h. With the increasing concentrations of SO^2-₃ (5, 25, 50, 100 mmol/L),the Fv/Fm, q_N，q_P and PS II in D. salina 1009 decreased, and the photoinhibition was obvious. Photoinhibition induced by SO^2-₃ in the presence of HCO^-₃ under high light intensity was reduced, and could be rapidly recovered under low light intensity(40 μmolm^-2s^-1). The results showed a protective role of HCO^-₃ against the SO^2-₃ damage under high light intensity (1000 μmol m^-2s^-1).

Abstract:Different methods of flowering regulation were used on oval Kumquat (Fortunella margarita Swingle), Ponkan (Citrus reticulata Blanco' Pokon' ) and Satsuma orange (C.reticulata Blanco' Miyagawa Wase') trees which were all grafted on rootstocks of trifoliate orange (Poncirous trifoliata) The changes in protein fractions during the flower initiation were determined by SDS-PAGE and IEF-PAGE. The results showed that flower numbers were obviously increased by girdling treatment and decreased by GA₃, and were also decreased by BA treated at the early stage of flower induction but increased by that at the late stage of flower formation. At the flower induction stage, some of the special proteins were observed in the buds treated with GA₃, but disappeared finally. In the flower primordium formation stage, the intensity of protein bands in the flower buds increased in the shoots girdled, and some special proteins were found in the flower buds. It is suggested that different methods of flowering regulation might result in different gene expression and characteristics of protein metabolism. Some protein with smaller molecules and lower isoelectric point were related to flower initiation of citrus trees.

Abstract:The experiments showed that the osmotic stress-induced inhibition of nitrogen fixation activity was mitigated to some extent by the introduction of mannitol into culture solution in Anabaena sp. strain 7120. It was shown that under dark condition or in the presence of photosynthetic inhibitors, such as DNP or CCCP, the beneficial effect of mannitol on nitrogen fixation activity was weakened or didrinished in Anabaena. Higher nitrogen fixation activity was observed in experiments with mannitol by adding O₂ together with Hi, but the activity was depressed by adding O₂ alone. When Anabaena cells submitted to osmotic stress were incubated in aerobic conidition (in air) the beneficial effect of mannitol was higher than that in anaerobic condition (in Ar or Nc. Beneficial effect of mannitol on nitrogen fixation activity of Anabaena was obviously strengthened by preincubation with 5% CO₂ or with 5% CO₂ plus 40% N₂, but it was abated by adding N₂ only. The mannitol-supported nitrogen fixation aCtivity in Anabaena was less evident in the presence of exogenous sucrose.

Abstract:Contents of IAA, GA_1＋4, ABA and iPAs were measured by enzyme-linked irnmunosorbent assay (ELISA) in leaves, panicles and anthers of cytoplasndc male sterile (CMS) rice Zhenshan 97A and its maintainer Zhenshan 97B during panicle development.From stamen and pistil formation to trinucleate pollen stages, IAA content in leaves of CMS line was shown to be lower than that of maintainer line, and the highest level was observed at binucleate pollen stage in maintainer line. So were IAA contents in anthers and panicles. Changes in GAsimilar pattern, i.e. in both lines, the level of GA_1＋4 rose at first, then dropped, however,the highest levels were found in leaves as well as in panicles and anthers of maintainer line during uninucleate to trinucleate stages. ABA level in leaves of CMS line were obviously higher than that in maintainer one at early panicle developmental stage, and was at nearly the same level in both lines at griddle stage, then again still higher than that in maintainer line. The levels of ABA in panicles and anthers in CMS line were also higher than those in maintainer line. As to the conteflts of iPAs. in leaves, panicles and anthers, markedly lower level in CMS line than in maintainer line was found at all stages. The ratios of IAA+GA_1＋4+iPAs to ABA in leaves, panicles and anthers of CMS line were also lower than those in maintainer one. It is proposed that the changes in contents of these phytohormones in CMS line are abnormal, and IAA, GA_1＋4 and iPAs deficiency and ABA accumulation aught be related to the generation of CMS in rice.

Abstract:Cotyledons from mature embryos of cassava cultivar Nanzhi 188 selected from cultivar CM321 - 188, which was provided by CIAT (Centro internacional de Agricultura Tropical), were used as explants. AgNO₃ could obviously promote the plant regeneration frequency (PRF) in the induction medium (MS I) with 16 mg L^-1 AgNO3 added at the 7th day, and in maturation medium (MS II) with 20 mg L^-1 AgNO, added at the 15th day, the PRF being from 40.5% (control) to 58.1 %, and from 36.1 % (control) to 61.3%,respectively. 0.25 mg L-1 ABA adding to MS I and to MS II could markedly improve PRF by 32.1 % and 45.2%, respectively. An decreasing concentration of 2,4-D at 2.0 mg L^-1 plus 16 mg L^-1 AgNO₃ and 0.25 mg L^-1 ABA in combination signifcanlly improved somatic embryo maturation and promoted to form normal shoots, the highest PRF was 95%, and the number of plantlets produced reached 39.6 per explant.

Abstract:Plant regeneration from in vitro culture of hypocotyl in three cultivars of Brassica alboglabra was studied. The results showed that shoots could be induced directly from both ends of hypocotyl fragments with optimum auxins of 2.0 mg L^-1 BA for cultivar 'Early Flowering', 0.3 mg L^-1 NAA+ 2.0 mg L^-1 BA for' Middle Flowering' and 0.5 mg L^-1 NAA+2.0 mg L^-1 BA for' Late Flowering', the corresponding shoot-induction frequencies being 84.6%, 86.7% and 93.3%, respectively. The optimum concentration of sucrose for shoot-induction was 1%. Addition of 4.0 mg La AgNO₃ and 500 mg L^-1 MES in the medium could greatly increase the frequency of shoot regeneration. The plant let could well develope after rooting in half strength MS medium supplemented with 0.1 mg L^-1 NAA.No morphological differences were observed between in vitro plants and seedling plants.

Abstract:Soil microorganisms, mainly bacteria, fungi and actinomycetes, under Eucalytus forest, Acacia forest and mixed forests were investigated during 1992 to 1993 in Huaxian county near Guangzhou. Soil enzyme activities, including cellulase, invertase, urease,proteinase and phosphate activities under different forest types were analysed. It was shown that mean annual amounts of soil dricrobes under forests are in order mixed forest>pure Acacia forest >pure Eucalyptus forest>barren and waste land. High activities of cellulase and invertase were found in "dxed forest of Acacia and Eucalyptus, while urease,proteinase and catalase in pure acacia forest. Soil respiration intensity was high in Acacia mangium forest and in its "dxed forest, and was low in Eucalyptus forest. Five years after forestation with tree species mentioned above on barren and waste land, the soil ndcroenvironment was shown to be greatly improved, which resulted in the increments of soil microbes under ground and of biomasses above ground.

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