Abstract:Two hybrid rice cultivars, super high-yielding Liangyoupeijiu (Pei'a i 64S×9311) and high-yielding Shanyou 63 (as control) grown in the field, wer e us ed to investigate the photosynthetic characteristics of highproduction during flag leaves development. It was shown that the contents of chl orophyll and Rubisco, the values of Fv/Fo, Fv/Fm, qP andφ_i in flag leaves of c v . Liangyoupeijiu were higher than those of the control, indicating that the fo rm er had greater capacity and higher efficiency for light energy absorption, transformation and utilization. The value of qN was higher and 1-qP/qN was lower in Liangyoupeijiu than in Shanyou 63, showing that the former was more tolerant to photoinhibition. Photo-carbon imbalance appeared in both cultivars during senescence of flag leaves, but which was less apparent in cv. Liangyoupeijiu. These beneficial factors in photosynthesis in cv. Liangyoupeijiu might be of importance in high production of super high-yielding rice.

Abstract:Citrus yellow shoot disease (citrus huanglongbing) leaves of Citrus maxima cv. Shatianyou collected from pommelo orchard in Meizhou, Guangdong Province, showed typical symptom of leaf mottling. The pathogen which was observed under electron microscopy was similar in morphology and structure to bacteria-like organism of citrus huanglongbing disease. Polymerase chain reaction (PCR) analysis also proved that the DNA of the pathogen was greatly homologous with PCR product from that of citrus huanglongbing pathogen. The result exhibits that the citrus yellow shoot could infect pommelo, which seldom appeared in this fruit.

Abstract:The effects of wax and cuticle of peanut seed coat on reducing the infection and aflatoxin production by Aspergillus flavus were studied. Experiments showed that when the wax on seed coat was removed with chloroform or/and cuticle removed with KOH (or cutinase), fungal infection rate and afiatoxin content in the seeds were significantly increased. Aflatoxin content in seeds with wounded seed coat was higher than that in intact seeds after being inoculated with A. flavus. Scanning electron microscopic observation on seed coat revealed that most of resistant seeds were rough in appearance and had adundant wax deposits on seed surfaces. It is indicated that the wax and cuticle play an important role in preventing fungal penetration.

Abstract:A mmopiptanthus mongolicus (Leguminosae) were subjected to ISSR (Inter-simple sequence repeat)-PCR analysis in order to investigate the genetic diversity within and among populations. Genomic DNA of A. mongolicus was extracted as the ISSR template, and the influencing factors of ISSR were studied and the experiment parameters were optimized. By adjusting template DNA concentration, Mg(supetscript 2+) concentration, dNTP and Taq polymerase contents, and annealing temperature, the PCR amplification conditions were optimized. The optimal experiment conditions were as follow: 20μ1 system containing 20 ngμ1^-1 template, 10 mmol/L Tris-HCl (pH 9.0), 50 mmol/L KCl, 0.1%Triton × 100, 2.75 mmol/L MgCl₂, 0.15 mmol/L dNTP, 2% formamide, 200 nmol/L primer, 1.5 U Taq polymerase. With a MJ thermal cycle, optimal amplification program was 1 cycle of 5 min at 4℃; 35 cycles of 30 s at 94℃, 45 sat 46-56℃, and 1.5 min at 72℃; 1 cycle of 7 min at 72℃; 30 min at 4℃, using block control style. One hundred ISSR primers were used to screen the suitable primers for assessing the genetic diversity of A. mongolicus, of which 15 ISSR primers with high resolution and multiple polymorphic bands were screened. The total 121 ISSR bands were amplified with 15 primers, and produced 43 polymorphic bands.

Abstract:Megasporogenesis and the development of female gametophyte in endangered Tsoonidendron odorum Chun were studied. The results showed that there were 2-5 ovules on the ventral surface of unicarpellate ovary wall. Ovules were anatropous, bitegminous and crassinucellar. Archesporial cell was one cell and differentiated from cell in the first or second layer beneath epidermis. The development of the embryo sac conformed to the Polygonum type. Abnormal development was observed at tetrad and mature embryo sac. Abnormal phenomena in the process of reproduction of Tsoongiodendron odorum causing this species to be endangered are discussed.

Abstract:The ultrastructure of root nodules of Elaeagnus conferta Roxb. and the activities of nitrogen fixation and hydrogen uptake were studied, The results show that Frankia hyphae exist at early stage in intercellular space in nodule cortex. The filamentous hyphae are branched with septa. Lipid bodies are distributed in infected young cells. The number of infected cells in mature nodules is much larger than that of young and senescent nodules. Apical endophytic hyphae swell to form lots of vesicles which are septate and double-walled. Vesicles are suggested to be importatant in nitrogen fixation. In senescent nodules, the vesicles disintegrate. Nitrogen fixation and hydrogen uptake activities in mature nodule is much higher than that in young and senescent nodules.

Abstract:The classification and geographical distribution of Rubus speci es in Jiangxi were studied by means of reviewing herbarium specimens, literatu res and field investigation. There are 43 species, 7 varieties and 2 forms of Rub us distributed in Jiangxi Province, among which Rubus inoper tus (Diels) Focke, R. eustephanus Focke ex Diels, and R. re flex us Ker var. lanceolobus Metc. are new records to Jiangxi P rovince. A key to all taxa ispresented, and the distribution of Rubus species is tabulated.

Abstract:Growth, N-fixation and heavy metal accumulation of Sesbania rostrata transplanted on acidified Pb/Zn tailings in Lechang, Guangdong Province, were investigated. Experiments were carried out by transplanting seedlings prepared with nutrition polybags of 9.5 cm in diameter and 10 cm height containing 1 kg soil (A), of 7.5 cm in diameter and 8 cm height containing 0.5 kg soil (B) and without polybag (C). The results showed that Sesbania rostrata succeeded to establish, grow and fix N on the tailings of pH 5-7, but failed to grow at pH<3. After transplanting on tailings for 84 days, the plant height (140-144 cm), basal diameter of stem (1.59-1.68 cm), individual biomass (36.6-38.8 g DW), dry matter production (5124-5432 kg hm^-2) and nitrogen accumulation (77-107 kg hm^-2) in treatments A and B were significantly higher than those in treatment C which were 117 cm, 1.35 cm, 20.2 g, 2828 kg hm^-2, and 40 kg hm^-2, respectively. The contents of Pb, Zn, Cu and Cd were highest in the roots followed by stems and leaves, and the amounts of the 4 heavy metals in whole plant were in the order Zn (186-221 mg kg^-1) > Pb (96-145 mg kg^-1) > Cu (17-30 mg kg^-1) > Cd (3-4 mg kg^-1). Transplanting seedlings with nutrition polybag could improve the growth and N-fixation, and markedly decrease heavy metals accumulation in S. rostrata. It is suggested that S. rostrata is a good pioneer species for bioremediation of the tailings.

Abstract:Based on a survey of the major trees grown on oil shale residue in Maoming, Guangdong, three species, (Vatica mangachapoi, Ormosia pinnata, and Khaya senegalensis) were chosen from 35 tree species for further study of their adaptation to such environment. The results showed that the net photosynthetic rates of the 3 species were significantly different, with a ranking of K. senegalensis> O. pinnata > V. inangachapoi. Diurnal variations of net photosynthetic rate in K. senegatensis and O. pinnata were great while that in V. mangachapoi was less. The ranking of their stomatal conductances was K. senegalensis > O. pinnata > V. mangachapoi. The difference in net photosynthetic rate among the three trees was related to the stomatal conductance. Though the net photosynthetic rate in K. senegalensis was higher, its intrinsic water use efficiency was lower than that in O. pinnata due to more water loss. The intrinsic water use efficiency of V. mangachapoi was much higher in the afternoon because of the lower stomatal conductance. The results indicate that K. senegalensis and O. pinnata might be more adaptable to the special environment.

Abstract:Carbon accumulation and distribution were studied in vegetation and soil for Pinus massoniana and Schima superba mixed forest ecosystem in Dinghushan Biosphere Reserve. The biomass of trees in three plots ranged from 174.41 t hm^-2 to 270.11 t hm^-2, with an average of 227.36 t hm^-2, which was contributed mainly by Pinus massoniana (54.9%-84.4%). The biomass of understory plants was 7.41-28.28 t hm^-2, with an averages of 14.41 t hm^-2. Standing stock of ground litter was 7.06-11.56 t hm^-2, with an average of 9.03 t hm^-2. Total carbon storage of the forest ecosystems ranged from 146.35 t hm^-2 to 215.30 t hm^-2. Of total carbon, 61.9%-69.9% was distributed by vegetation component, 28.5%-35.5% by soil, only 1.6%-2.8% by standing ground litter layer. Potential carbon sequestration in forest vegetation is discussed.

Abstract:Based on meteorological data recorded for about 3-5 years in four forests at different elevation in Dinghushan Biosphere Reserve, the differences in forest temperature and moisture were analyzed. The results showed that the mean air temperature and relative humidity in Pinus massoniana forest, broad-leaved and coniferous mixed forest, ravine rain forest, and mountain evergreen broad-leaved forest were 22.7℃, 80%; 20.9℃, 82%; 20.4℃, 87%; and 19.2℃, 81%, respectively, while annual mean daily range of air temperatures were 5.9℃, 4.6℃, 3.6℃, and 3.1℃, respectively. The capacity of the decrease of maximum air temperature in forests was the principal factor of decreasing the annual mean differences in daily range of temperature. The moisture degree indicated that all the four forests were humid annually, but different monthly. Analysis showed that differences in temperature among the four forests were caused by the changes in micro-topography, vegetation type, and altitudinal level. To rationally evaluate the effect of various forests on microclimate, we must consider the differences caused by factors as mentioned above.

Abstract:Thirty-eight newly recorded fern species in Guangzhou are presented , which belong to 9 genera(Angiopteris, Gonocormus, Pityrogramme, Ath yriopsis, Macrothelypteris, Woodwardia, G y mnosphaera, Hemigramma, and Colysis) and 3 familie s (Angiopteridaceae, Hymenophyllaceae, and Gymnogrammaceae).

Abstract:Pollen fertility, seed-set and incidence of apomictic and sexual embryo sacs in Apluda mutica under different photoperiods were investigated. There were no differences in pollen fertility between treated and untreated plants. No difference in the rate of seed-setting was found between decreasing photoperiods and natural photoperiod. Flowering and seed-setting were retarded greatly as photoperiod was greater than natural photoperiod during inflorescence development. Frequency of apomixis was from 0.41 to 0.64 when the plant was exposed to natural photoperiod, and to that with addition of one hour. The frequency of apomixis reduced to 0.19-0.22 if natural photoperiod was decreased by 1 or 2 hours, or increased by 2 hours, showing that the frequency of apomixis was greatly reduced as compared to the control or to the condition of natural photoperiod with one hour increase.

Abstract:Study on ecological functions of the herbaceous layer in forest ecosystem conducted in the last two decades is reviewed. The concept of herbaceous layer in forest ecosystem is defined as living grasses and forbs, and tree seedlings usually lower than 40 cm. Herbaceous layer, together with litter, and ambient soil constitutes an understory sub-ecosystem. Herbaceous layer has been reported to have a lot of ecological functions, such as increasing ecosystem diversity, preventing water and soil loss, enhancing soil nutrition, amending soil structure, improving seedling growth, improving microclimate, and accelerating ecological restoration. However, there are several aspects that should be paid more attention in the study on herb layer in the low subtropical forest ecosystem, e. g. 1) ecological functions and benefits of herbaceous layer or litter; 2) the colonization and succession of herbaceous layer in understory of artificial forests; 3) mechanism of seedling renovation in the forest; 4) the eco-functions and mechanisms of herbaceous layer in agroforestry ecosystem; 5) screening for more excellent herbaceous species.

Abstract:Community invasibility is a focus research in invasion ecology. Fact or s influencing the invasibility are reviewed including evolutionary history, comm unity structure, propagule pressure, disturbance and stress. Related hypoth esis and experimental research on the effects of community structure (species compos ition, species diversity and species functional groups) on invasibility a re pres ented. The relationship between environmental stress and invasibility ar e also e xpounded.

Abstract:This paper presents recent advances in apomixis studies on embryology and genetics in guineagrass(Panicum maximum Jacq.). So m e problems in relation to apomixis reaserch on guineagrass are discussed. It i s pointed out that guineagrass is a promising material both for theoretical an d a pplied studies of apomixis.

Abstract:Plant gene engineering was paid more attention to and resulted in many excited achievements during the past decade. In this paper, significan t progress in molecular breeding of ornamental plants, and the strategies and m et hods of molecular breeding are reviewed. The significance of application and developing molecular breeding in ornamental plants in China is discussed and emphasized.