Abstract:One-year-old seedlings ofteak （Tectona grand/s L. f., Verbenaceae） from tissue culture were potted for simulated acid rain experiments in Guangzhou. Acid solution was prepared with H²SO⁴ and HNO³ adjusting to pH2.5, pH4.5 and pH6.5 for control. Seedlings were applied with acid solution once with 3 days after potting for 4 weeks from 10 June to 20 October, 2000, to study the effects of stimulated acid rain on the growth, photosynthesis and water use efficiency in teak. The results showed that the morphological parameters of the investigated seedlings were influenced significantly by acid application although no statistical difference in physiological parameters were found among treatments. The basal diameter （D） and plant height（H） of teak, particularly their combination （D₂H） declined under pH4.5 and pH2.5. There were no difference in net photosynthetic rate （Pⁿ）, transpiration rate （E） and stomatal conductance （g^s） between different treatments. For all treatments, Pⁿ was positively correlated with g^s, especially under pH4.5, but the relation of E with g^s was relatively low. Diurnal changes in water use efficiency （WUE） of the plants treated with pH4.5 and pH2.5 solutions were quite similar with the exception of those treated with pH6.5. The average ratio of intracellular CO² concentration and ambient CO² concentration （Cⁱ/C^a） was lowest in control （pH6.5）, compared with other two acid treatments, implying that teak in the control was most effective in CO² utilization.

Abstract:Changes in Photosynthetic parameters were examined of Cassia data L. and Syzygium cumini （Linn.） Skeels grown on waste residue of oil shale from Maoming Petrochemical Company as polluted site, and at Maoming forestry institute as control site. Results showed that absolute values of net photosynthetic rate, stomatal conductance, and transpiration rate in C. data, were higher than those in S. cumini at most hours in the daytime at both sites. Reductions in net photosynthetic rate and water use efficiency in C. data. were greater than those in S. cumini, whereas, stomatal conductance was the contrary, which might be related to the water content in soil at different experimental sites. It was shown that S. cumini was more resistant to oil shale pollution than C. data. More comprehensive physiological indexes in selecting pollution-resistant plant species are desirable.

Abstract:The nutrient dynamics during the decomposition of coarse woody debris （CWD） with different diameters from Castanopsis chinensis in Dinghushan monsoon evergreen broadleaved forest, Guangdong Province, was examined by sampling debris that were at various decaying stages. Changes in debris density were measured in debris with diameters of 5-10 cm （grade 1）, 10-20 cm （grade 2） and 20-30 cm （grade 3） to study the composition rates, nutrient dynamics, and substrate quality during decay. Up to decay stage HI, CWD grades 1, 2, and 3 lost its weight and carbon by 36%, 48% and 43%, and 33%, 47% and 19%, respectively. The concentrations of N, P, Mg, Ca and Na increased while C and K decreased. The increase in element content was likely due to lower leaching rate campared to the loss of CWD mass. N accumulation in CWD might be caused by nitrogen fixing bacteria and fungi. The change in ratio of N to P showed a good decomposition indicator in CWD. The release of carbon and other main nutrients was slow, thus CWD exhibited an important long-term carbon sink in the forest.

Abstract:LEAFY is an important regulator of floral meristems genes in higher plants. To investigate its origin and evolution, a LEAFY homologs with length of 2 866 bp was cloned from Capsella bursa-pastoris genome using the conserved primers from Arabidopsis thaliana LEAFY gene. Sequence analysis indicated three exons with the length of 457 bp, 407 bp and 411 bp. These exons encoded a protein of 424 amino acids. The single exon was more than 90% homologous to A. thaliana LEAFY gene, and the amino acid homology was 86%. When compared to Arabidopsis lyrata LEAFY gene, there was 93 nucleotide substitution in the exons of C. bursa-pastoris, and 74.7% of these mutations located at the third position ofcodon, the amino acid homology reached 90%. Among the three exons, Ds/Dn ratio was 1.9, 2.3 and 6.0. Homologous comparison indicated that the C-terminal amino acids were highly conserved among different plant species while the great variation existed in N-terminal. In addition, the Arg mutation located at 346 in CapLFY gene was speculated to be one of main reasons that caused the ecotypes with different flowering time in C. bursa-pastoris.

Abstract:The analysis of genetic diversity among tomato cultivars was compared by simple sequence repeat （SSR） and morphological markers. Seven SSR primers were used to detect the genetic diversity among 11 tomato cultivars, and total 53 bands were obtained, the average bands per SSR primer pair being 6 with a range from 2 to 9. Mean genetic similarity coefficient among cultivars was 0.60, varying from 0.39 to 0.84. According to 11 phenotype values of morphological characters, the mean genetic similarity coefficient was 0.58, varying from 0.27 to 0.72. Cluster analysis by unweighted pair-group method with arithmetic mean （UPGMA） showed that both SSR and morphological markers could well distinguish the tomato cultivars by the colour of mesocarp and fruit size. The results of the evaluations of genetic diversity in tomato cultivars based on the two methods were similar.

Abstract:Crude proteins from green leaves ofBrassica campestris L. ssp. chinensis （L.） Makino var. utillis Tsen et Lee and Lactuca sativa L. were subjected to acetate cellulose membrane electrophoresis under SDS-denatured conditions. Two groups of protein were observed, one migrated towards the anode, and the other, the cathode. The cathode protein from Brassica campestris ssp. chinensis vat. utillis was collected from cathode reservoir after SDS-PAGE, and its amino acid components were determined to have 57.0% phenylalanine, the ratio of basic/ acidic amino acid residues was 3.04, indicating the protein towards cathode was a phenylalanine rich basic protein. It must be emphasized that the protein migrated towards the cathode had never been reported previously.

Abstract:Pollen tube growth in the ovary of Phaius tankervilliae （Aiton） BI. （Orchidaceae） as observed under scanning electron microscope could be divided into three stages. In first stage, from the beginning ofpoUination to megaspore tetrad, pollen tubes grow axially, passing through gynostemium to the ovary and from proximal placenta along ovary wall develop upward. In second stage, after 2-nucleate embryo sac development, most pollen tubes grow radially around ovules. In third stage, at maturing of the embryo sac, pollen tubes grow directionally toward micropyle into embryo sac. It is suggested that directional growth of pollen tubes are controlled by molecular signal in ovule.

Abstract:Developmental anatomy of trichomes （glandular hairs and non-glandular hairs） on the leaves and stems ofLanvandula pinnata was studied. It was shown that all trichomes are originated from the protodermal cells, but their structure, development and function are distinctly different. There are two types of glandular hairs, capitate glandular hairs and peltate glandular hairs, all of which are composed of a basal cell, a stalk cell and apical secretory cells. There are 1 or 2 secretory cells in a capitate glandular hair but 8 secretory cells in a peltate glandular hair. However, Non-glandular hairs consist of 3-20 cells, they can be divided into 3 kinds： uniseriate, two-branched, three-branched and more branched arborization. In non-glandular hairs, the apical cells become tapered. The glandular hairs are formed by second successive periclinal divisions of the initial cell, and because of the different meristematic state of the stalk cells and apical cells, they developed into two types, capitate and peltate. Non-glandular hairs are created from initial cells through second or more periclinal divisions and unequal divisions, then developed into several to about twenty sister cells.

Abstract:The experiments of potassium nutrition in papaya （Carica papaya L.） showed that leaf blight was caused by available potassium deficiency in soil where papaya was planted. Application of potassium fertilizer could effectively control such disease and get higher yield. In the roots, stems, leaves and petioles of papaya with leaf blight which was caused by potassium deficiency, the contents of magnesium were obviously increased, indicating the antagonistic effect between the two elements in papaya plants.

Abstract:Microrhizome of Zingiber officinale Rosc. cv. Jiushan were inducted from tube plantlets, which were derived from explant of stem tip, cultured on MS medium supplemented with 0.2 mg L^-1 BA and varying concentrations of combinations of sucrose, NAA, Ca₃（PO₄）₂, Paclobutrazol （Pac）. The results showed that rhizome production was best in tube culture on MS medium supplemented with 0.2 mg L^-1 6-BA, 0.5 mg L^-1 NAA, 2.5 mg L^-1 Ca₃ (PO₄)₂, 2.5 mg L^-1 Paclobutrazol and 8% sucrose. NAA and 6-BA had no promotion effects on rhizome induction. More illumination stimulatory rhizome growth of the ginger.[

Abstract:Propagation of Cymbidium kanran Makino by using rhizomes as explants to study the effects of growth regulators on the induction, multiplication and differentiation of protocorm-like bodies （PLBs）, and the rooting. The results showed that the optimal medium for induction of PLBs was B₅ containing 0.50 mg L^-1 TDZ and 0.25 mg L^-1 NAA, in which induction rate of PLBs was 98.3%, for multiplication of PLBs it was B₅ containing 1.0 mg L^-1 uniconazole （S-3307） and 0.2 mg L^-1 NAA and 3.5% sucrose, the multiplication coefficient being 9.4. For differentiation it was best on B₅ medium containing 0.75 mg L^-1 S-3307, 1.0 mg L^-1 6-BA and 0.4 mg L^-1 NAA, in which the differentiation rate was 87.8%. As for rooting, 1/2B₅ supplemented with 0.2 mg L^-1 NAA and 0.05% active carbon, in which rooting rate reached 100%.

Abstract:Five phenolic compounds, gallic acid （1）, protocatechuic acid （2）, ethyl gallate （3）, ferulic acid （4）, and kaempferol 3-O-α-L-rhamnopyranoside （5）, were isolated from the leaves of Cephalomappa sinensis. Their structures were elucidated by spectroscopic analyses （IR, NMR, MS） and the spectral data were compared with those in literatures. All the compounds were isolated from this species for the first time.

Abstract:Five species of Pittosporum were reported as new records to 3 provinces in China, i.e. Pittosporum subulisepalum Hu et F.T.Wang for Sichuan;P. tubiflorum H. T. Chang ＆ S. Z. Yan, P. glabratum Lindley and P. illicioides Maldno for Yunnan; and P. xylocarpum Hu ＆ F. T. Wang for Guangdong.

Abstract:This paper reviews the recent advances in the studies of the control of invasive weed Mikania micrantha H. B. K. in tropical and subtropical Asia. At present, manual removal, herbicides, ecological control and biological control are included in the control ofM. micrantha, in which biological control is one of the most promising ways. I nsects A ctinote thalia pyrrha and A. anteas are effective for the control of the weed. The fungus Puccinia spegazzini can inhibit the weed growth and even kill it, so it may be useful in China. Trees such as Delonix regia, Macaranga tanarius, and Heteropanax fragrans have allelopathic effect on M. micrantha, which could inhibit the regeneration ofM. micrantha. Parasites of three species of Cuscuta, i.e.C, campestris, C. Chinensis and C. australis can effectively kill the aerial parts of the host weed M. micrantha within 72 days.

Abstract:With the rapid development of molecular biology, series of genes including effective and regulatory genes that respond to salt stress have been found. This paper summarizes progress in the study on improving plant salt resistance by genetic engineering in recent years and some problems that wait to be resolved．