Abstract:Based on the 3'-end conserved regions among genomic RNA of tobamovirus, three primers P1, P2, P3 matching them were synthesized. ds-cDNA were synthesized to leading by these primers and cloned into the vector pBS. Fifteen positive recombinants were obtained after Hind Ⅲ + PstⅠ were digested. Among them, pBF3 was sequenced. It showed that the fragment of 2432 bp had two open reading frames (ORF). The first ORF encoded the frangipani mosaic virus movement protein. It ranged from nucleotide 806 to 1576. The deducing protein co nsisted of 256 amino acids．with a calculated MW of 28。5 kilo dalton．The second ORF encoded the coat protein which ranged from nuclco tide 1 635 to 2 158，and the deducing protein co nsisted of 1 74 amino acids，with a calculated MW of l9.4 kilo dalton． This frgment also included partial regions of 180 kDa protein and 3'-end non-coding regions．

Abstract:A short photoperiod and low temperature-induced male sterile rice Yi-DIS was crossed With some rice varieties to examine the pollen fertility of parents and F₁ under natural low temperature, and to investigate the fertility segregation of F₂ and F₃ during stable phase in sterile line. The results showed that the stability of fertility in parents and F₁ was affected to a certain extent by low temperature. Besides the sensitivity of male parent to low temperature, pollen fertility in F₁ was also related to some other factors，and the fertility stability in F₁ might result from heredity，The characteristics of male sterile Yi-DIS basically accorded with genetic mode controlled by two pairs of independent major genes，and was affected probably by many minor genes． It seems that the two pairs of restoring genes corresponding to this two pairs of major genes were different in genetic effect．

Abstract:The investigation of plant nutrient contents in Dinghushan lower subtropical evergreen broad-leaved forest was carried out in August 1996. Sampling was made in Dinghushan Biosphere Reserve, Guangdong, from tree, shrub, liana and herb layers with 5-8 representative species each. It was shown that the nutrient contents in leaves of all plants were N 0.946%-2.535%, P 0.030%-0.127%, K 0.614%-1.833%, Ca 0.442%-1.995% and Mg 0.024%-0.188%. Average contents of nutrient elements in various organs and at different layers in the forest were varied．Average nutrient content of N was highest in leaves，and in descending order in barks，branchcs，root and stems；other elements：P in leaves > branches > roots > barks >stems；K in leaves > branches > barks > roots > stems；Ca in barks > leayes > branches > roots > stems；Mg in leaves > stems > roots > barks > branches．The distribution of elements in most plants was as follows： N > Ca > K > Mg > P in leaves，branches and roots；K > Ca > N > Mg > P in stems；and Ca > N > K > Mg> P in barks. The factors，especially P and Mg，possibly limiting the plant productivity in the area studied are discussed．

Abstract:This paper presents the results of a cladistic analysis and the evaluation of intergeneric phylogenetic relationships within the Magnoliaceae based on morphological, anatomical, and cytological data. In the cladistic analysis, the genus Degeneria is chosen as outgroup. The outgroup comparison method and the fossil evidences are used in polarizing the characters. A data matrix consisting of 23 taxa and 32 characters is analyzed using PAUP 3.1.1 in Macintosh computer and Hennig 86 v. 1.5 in IBM computer, and 44 equally most parsimonious cladograms are produced. The strict consensus cladogram shows that：(1) the genus Magnolia is a polyphyletic group，in which sect．Maingola has a sister-group relationship with the genus Manglietia，and sect．Theorhodon has a close relationship with the genus Talauma；(2) the genus Alcimandra and the tribe Michelia form a monophyletic group；(3) it supports that the genus Liriodendron is isolated in Magnoliaceae and has been branched off from the ancestor of the family in an early stage and it developed in its own pattern．

Abstract:A new name, Primula sinoexscapa, is proposed for the species Primula exscapa described by Chen et C. M. Hu in 1990 from China, which is a later homonym of Primula exscapa Hegetschw., F1. Schw. 195. 1838.

Abstract:A comparative study was undertaken on the leaves of eight Uvaria, threeCyathostemma and one Ellipeia species in order to investigate interspecific anatomicaldifferences which could be useful in species identification and their taxonomic significance.Anatomical characters that are of significance are terminal sclereids, druses in epidermalcells, trichomes, brachysclereids in parenchymatous tissues of midribs and petioles, and theshape of midribs and petioles in transverse sections. Certain features are present in certainspecies only and are thus useful for species identification. The results also show that thethree genera are quite closely related.

Abstract:Ultrastructural observation of chloroplasts in different sections of young and mature leaves of Cymbidium sinense (Andr.) Willd. showed that the grana in chloroplasts of mature leaves were well developed, with tight thylakoid membrane. Osmiophilic granules in young leaves were few, whereas those in mature leaves were many, and so were the starch grains. In comparison with mature leaves, fewer grana, smaller chloroplasts and lower photosynthetic oxygen evolution rate were found in young leaves. In young leaves，chloroplasts in leaf apex were biggest，and in leaf base， smallest，but lower oxygen evolution rate was shown in leaf apex．No significant difference was found in chloroplast size and chlorophyll content among various parts of mature leaves．Chlorophyll content is not in direct proportion to oxygen evolution rate．

Abstract:Three cultivars of 15 to 20-year-old litchi (Litchi chinensis Sonn.) trees grown at Zhangzhou, Fujian Province, were chosen for the experiment. Cultivar Wuye is normal in embryo development, cv. Luhebao being abortive, and cv. Lanzhu having both normal and abortive embryo development. Polymine (PAs) contents in the ovules were tested at 7, 14, 22, 31, 41 and 52 days after anthesis, i.e. from the stage of polar nuclei division to cotyledonary embryo stage, which coincided respectively with each stage of embryo development．The results showed that the contents of putrescine (Put)，spermidine (Spd) and spermine (Spm) in normal ovules were al1 higher than those in abortive ones during the whole embry ogenetic process，and reached highest level on the 7th day after anthesis，with Put content being the richest．The contents of these PAs appeared subsequently a downward tendency．However，Spm content increased slightly from the 22nd day to 31st day after anthesis (from globular to heart stages) in normal ovules．But such a phenomenon did not appear in the abortive ones．The contents of Spd and Spm evidently dropped more rapidly in the abortive ovules than those in the normal，which indicats that 1ower contents and more rapid decrease of Spd and Spm during embryogenetic process might have a close relationship with embryo abortion．The studies also showed that low ratios of (Spd+Spm)/Put and Spm/PAs might hindered embryo development．PAs contents hit the peak before the contents of DNA and protein reached maximum，which suggests that PAs might affect embryo development by regulating the synthesis of biomacromolecules．

Abstract:Drought, salt and chilling effects on proline accumulation were studied in 3-leaf-stage seedlings of three rice (Oryza sativa L.) varieties: IAC (sensitive to drought and salt, and tolerant to low temperature), Dahuanggu (salt-resistant but sensitive to low temperature) and Guixi (drought-tolerant). Treatments were carried out at -0.6 MPa PEG (simulation) for drought, 0.15 mol/L NaC1 for salinity, and 6 ℃ for chilling stresses. Proline content in aboveground part of rice seedlings were tested. The results showed that proline accumulation in rice seedlings of various varieties was seen under all stresses，and the proline content increased with increasing time of stress．Sensitive variety accumulated more proline content than tolerant one. It seems，however, that proline accumulation can not be used as a screening index of resistance to stres ses in rice seedlings.

Abstract:Cold tolerance in seedlings of 5 japonica rice varieties, of which 3 from Japan and 2 (Taizhu 157 and Jianan 20) from Taiwan, and 1 indica rice variety Tesan'ai 2, was studied in Phytotron with light intensity of 1000 and 2000 1x at average temperature of 8.5℃, relative humidity of 75%, and 12 hours of photoperiod per day. Rice seeds were sown in Guangzhou in December 1999. Twenty-day-old seedlings were put into phytotron for 9 days of treatment. The morphological and physiological characteristics, such as plant height，leaf number of main culm，dry weight of shoot， death percentage， chlorophyll content and electrolyte leakage rate were determined ．The results showed that japonica rice Nihonbare，Kinmaze, Fukuhikari and Taizhu 157 had greater tolerance to low temperature than Jianan 20 and indica rice Tesan'ai 2．The japonica rice varieties with cold tolerance will be good donors of cold-tolerant genes for improving indica rice varieties， which will be helpful for preventing the seedlings from cold injury in the early cropping season in Guangdong，China．

Abstract:The contents of IAA, GA3, ZT, and vitamins B2, C, E and carotenoid in pollens of rice, maize and Chinese pennisetum stored at 4 ± 1 ℃ decreased with duration, on the contrary, ABA content increased. IAA and GA3 contents and the respiratory rate in longlived pollens of Chinese pennisetum were lowered as compared to those in short-lived pollens of rice and maize, but ABA level in Chinese pennisetum pollens was consistently raised.

Abstract:When detached leaves of maize (Zea mays L.) were treated with AsA, NADPH and DTT solution, the xanthophyll cycle and non-radiative energy dissipation (NRD) all changed correspondingly in certain degree. 20 mmol/L AsA could markedly promote the deepoxidation of violaxanthin (V) to zeaxanthin (Z) via antheraxanthin (A), the non-photochemical quenching (NPQ) value and Fv/Fm both apparently increased, but Z is easily to be saturated under high light (>650 μmol m^-2s^-1). 5 mmol/L DTT inhibited the formation of Z significantly，and slightly affected A content．In the same condition．the NPQ value and Fv/Fm of maize leaves all rapidly decreased．0.5 mmol/L NADPH also inhibited the transformation of V to Z， but this effect was reduced under hight 1ight condition．The corresponding NPQ value and Fv/Fm all decreased following the decrease of Z．In summary，this three kinds of treatments all affected the NRD through changing the contents of Z and A，but not the size of xanthophyll pool．

Abstract:Four triterpenoid saponins along with three triterpenes, oleanolic acid (1), ursolic acid (2) and hederagenin (3) were isolated from the leaves of flex kwangtungensis. By spectroscopic and chemical methods, the structures of the four saponins were identified as 3-O-β-D- glucopyranosyl-(1 →3)-α-L-arabinopyranosylxileanoli acid (4), 3-O-β-D-glucopyranosyl- (1→2)-α-L-arabinopy-ranosylxileanol acid (5), 3-O-β-D-glucopyranosyl- oleanolic acid (6) and 3-O-β-D-glucopyranosyl(1→ 2)-β-D-galactopyranosyl-oleanolic acid (7).This paper is the first report of the chemical constituents from this plant.

Abstract:The type specimens of Philadelphus kunmingensis S. M. Hwang and var. parvifolius S. M. Hwang was indicated.

Abstract:Explants from dormant bud segments and from epicotyls and hypocotyl of the seedlings of Michelia maudiae Dunn were cultured on MS medium supplemented with various concentrations of NAA, 2,4-D, BA alone or in combination. Medium with 2,4-D could only produce calluses. A large number of adventitious buds and some calluses were observed on medium containing BA (3.0 mg L^-1) and NAA (0.2 mg L^-1). Calluses from original explants generated a maximum number of shoots in subculture on MS medium supplemented with BA (2.0 mg L^-1)and NAA (0.2 tag L^-1)．Planflets rooted well on 1/2 Ms medium containing 0.5 mg L NAA with 1.0％ active carbon． The plantlets were transferred to pots containing a perlite/coconut fibre and (2：2：1) mixture which grew normally with a survival rate of 92％．

Abstract:This paper reviews the research history of acid deposition, and summarizes the effects of acid deposition on forest ecosystems. Studies on the relationships between aluminum toxicity and forest decline under acid deposition in the last two decades are also reviewed, which is shown that aluminum toxicity is an important factor led to forest decline. Certain questions associated with the study methods and approaches to the study on aluminum toxicity to forest decline are proposed.