Abstract:Meliaceae is a pantropical family comprising about 51 genera and 550-600 species mainly distributed in tropical Old World.Tropical Asia and Tropical Africa are the two present distribution centres of the family.There are 15 genera and 61 species in China which constitute 29% and 10% of the total genera and species in the family,respectively,and they mainly distribute in the southwest and the south of China.The 15 genera of chinese Meliaceae may be divided into 5 distribution patterns:1.Tropical Asia,Africa and Central to South America disjunction(1 genus),2.Old World tropics(3 genera);3.Tropical Asia and Tropical Australasia(2 genera),4.Tropical Asia to Tropical Africa(1 genus);5.Tropical Asia(8 genera).The species distribution of Chinese Meliaceae may be divided into 2 types:1.Indo-Malesian(31 species);2.Endemic to China (29 species).The Meliaceae of tropical Asia entered Yunnan,Guangxi and Hainan of China through Indo-China,while the Meliaceae in the Philippines is in direct connexion with those in Taiwan of China.China has no endemic genus of Meliaceae.All the species common to China and outside China are of tropical Asia distribution type, and so they are common in origin.The time of the origin of Meliaceae might be inferred in Upper Cretaecous.

Abstract:The paper deals with the chromosome numbers and karyotype analyses of six species of Artemisia from southwestern China.Their karyotype formulae are as follows:A.japoniaThunb.,2n=18=12m+6sm(2SAT); A. parviflora Buch.-Ham.ex Roxb.,2n=36=30m+4sm+2st(6SAT);A.dubia Wall.ex Bess.,2n=36=28m+8sm(2SAT),A.myriantha Wall.ex Bess.,2n=36=30m+ 6sm,A.lavandulaefolia DC.,2n=54=42m+12sm;A.velutina Pamp.,2n=54=36m+18sm.

Abstract:Four new species of Mitreola from Guangxi of China are described.They are Mitreola pingtaoi D. Fang et D.H.Qin,M macrophylla D.Fang et D.H.Qin,M.spathulifolia D.Fang et L.S.Zhou and M.purpureonervia D.Fang et X.H.Lu.

Abstract:Studies on the formation of the pre-developed embryo of rice(Oryza sativa L.)rariety(PDER)indicate that PDER is diploid,with chromosome number 2n=24. About 50% of the embryo sacs of this variety can give rise to embryo from unfertilized egg cells.The seeds so formed show higher germination rate and produce more vigorous plants.Some of the megasporocytes do not undergo meiosis but divide mitotically to give rise to diploid embryo sacs indicating that PDER is an apomictic type of plant showing diploid pargthenogenesis(diplospory).The apomictic embryo sacs have the following characteristics:1.The transition period from the archesporial cell to the megaspore mother cell is much prolonged.Thecytoplasm of the archesporial cell and the megaspore mother cell appears less dense in comparison with that of the surrounding nucellus cells.2.After the second mitotic division the megasporocytes give rise to three uniserially arranged cells.Two cells near the micropylar end degenerate.The cell near the chalazal end becomes the functional megaspore.In some embryo sacs all three cells degenerate resulting in the formation of degenerated embryo sacs.3.The functional megaspore divides three more times(mitotically)to give rise to an 8nucleate embryo sac.The 8-nucleate embryo sac produces seven cells similar to those seen in normal(i.e.non-apomictic) embryo sacs.The morphology of the synergids is,however,slightly different.In the apomictic embryo sacs the synergids appear much elongated and they do not tightly surround the egg cell.

Abstract:An ultrastructural study of the cellular events during the early stages of organization in the zones of localized active cell division was made in the callus cultures of Stevia rebaudiana.The callus cultures undergo marked changes in structure when transferred to a differentiating medium containing benzyladenine,which is known to induce organ differentiation in this system.Cells within meristematic regions formed in the callus have small size,large nucleus,some of which contain intranuclear inclusions,with both prominent and vacuolated nucleolus and numerous small vacuoles distributed around the periphery of the cell or dispersed throughout the cytoplasm.In many cases,the presence of cytoplasmic and membranous protrusions was observed in the vacuoles,some of which is in close association with dilated endoplasmic reticulum.Multiple and double membrane-bound concentric structures derived from endoplasmic reticulum were often observed as well.Dictyosomes and their associated vesicles are common,sometimes appear in groups.The cytooplasm contains ribosomes,which are occasionally seen as clusters of polysomes.Therefore,cells within meristematic regions are similar to the vacuolating and dividing cells of meristem.Another distinctive feature of these cells is the appearance of plasmalemma invaginations.They increase the surface area of the plasmalemma of the cell and may facilatate the absorption of the digested contents of neighboring crushed callus cells.It is concluded that these ultrastructural events reflect some morphological changes which precede organ differentiation in the cultured callus of Stevia rebaudiana.

Abstract:Stenotaphrum secundatum(Walt.)Kuntze and Axonopus conpressus(Swartz)Beauv.are good lawn grass species in tropical and subtropical zones.Their stoloniferous stems producing roots and tillers in each node cover a large area. The widely developed and well maintained root hairs of S.secundatum and the creeping character of A.compressus show that both plants are the promising plants for soil conservation.Anatomical study indicates that the densely arranged bundles and well developed sclerenchyma in the stem and leaf of S.secundatum make the plant tenacious.The dissections of vascular bundles in leaves of both species show garland structure,and thus,they are considered as C.plants.

Abstract:The NaCl-induced inhibition of nitrogen-fixing activity of blue-green algae Anabaena 7120 was removed to a certain degree by the introduction of appropriate KNO3 into the culture medium.When the preincubation of algae cells was done in dark before experiment for 24 hours or in the presence of photosynthetic inhibitors,such as DNP or CCCP, the benefical effect of KNO₃ on the nitrogen-fixing activity of Anabaena treated with NaCl stress weakened or disappeared.In the addition of O₂ together with H₂ the mitigative effect of KNO₃on nitrogen-fixing activity of Anabaena was reinforced under NaCl stress.But a marked inaction in nitrogen-fixing activity of Anabaena occurred under NaCl stress when O₂was introduced into the test system alone.When algae cells treated with NaCl stress were incubated in the aerobic condition(in air)the benefical action of KNO₃ was higher than that in anaerobic condition(in Ar).The KNO₃supported nitrogen-fixing activity of Anabaena was more evident under NaCl stress in the prensence of the exogenous sucrose or CO₂.The migatative effect of KNO₃ on nitrogen-fixing activity of Anabaena was accelerated under NaCl stress in the addition of N₂ together with CO₂, while it was depressed by adding N₂ alone.

Abstract:Buds of Acacia auriculiformis and A.mangium from 4-year-old mother trees were first sterilized in 6% chloros for 20 minutes,and then in 0.1% mercuric chloride for 5 minutes.Multiple shoot induction was obtained through culturing on MS basal medium supplemented with 10μmol/L BA and 0.5μmol/L IBA.Large explants were easier to induce multiple shoots than small ones.66.7% of large explants of A. auriculiformis and 60.0% of A.mangium explants produced multiple shoots,the largest shoot number per explant reached 55 and 48 respectively.Root induction was done on half concentration of MS inorganic compounds supplemented with formal MS organic compounds, 4.92-7.38μmol/L IBA and 2.69μmol/L NAA medium.Rooting percentages of A.auriculiformis and A. mangium shoots were 29.8% and 25.0%,respectively.The frequency of rooting also related with shoot's health and its physiological state.Subculture can rejunvenate plant tissue,increase the number of shoot per explant and promote rooting.Vigorous plantlet can be obtained when the rooted-shoots were transplanted to soil after two-week training.

Abstract:Three hybrid rice combinations, with resistance, susceptibility and hypersensitivity to bacterial blight of rice,namely V6(R),U1/312(S)and S63(HS),were inoculated with Xanthomonas oryzea pv.oryzea 76-25 strain with strong virulence at the three-leaf stage,the uninoculated plants were used as control.The leaves were taken for biochemical analysis after 72 h of inoculation.The results showed that both PAL and POX activities were increased,while the SOD activities were decreased and the MDA content was increased.The changes of all above indexes of resistant combination V6 were more significant than that of susceptiblecombinations U1/312 and S63. However,the decrease of soluble protein content in the leaves of U1/312 and S63 were more significant than that of V6.

Abstract:Cuttings of Chamelaucium umcinatum and Correa reflexa in the plastic chamber enriched with CO₂ both day and night at an average level of 800μl L-1 showed a significant increase of dry weight and starch content.In comparison with control,the short time of recovering of starch content to initial level and a progressive rise of starch content in high CO₂ treated cuttings resulted in the earlier rooting, higher rooting percentage and more roots. After cutting for 40 days,the rooting rates of the CO₂ enriched cuttings of Chamelaucium uncinatum and Correa reflexa were respectively 26.6% and 33.4% higher than that of the controls.However,the effect of CO₂ enrichment on cuttings of Prostanthera was inconspicuous,probably because these cuttings were insensitive to CO₂ treatment.

Abstract:To determine the activity of endopeptidease and the degradation of arachin in cotyledons of varying vigour peanut seeds during germination, the new harvested peanut seeds(as seeds of high vigour)were stored under relative humility of 95±1% at 28℃ (as seeds of medium vigour)and 40℃(as seeds of low vigour)for 7 days.After the treatment,the vigour index,endopeptidase activity and rate of arachin degradation were reduced.The isoenzyme of endopeptidase also changed.A new isoenzyme exhibited on PAGE in cotyledons of germinating seed of medium vigour on the 3rd to 6th days,and seeds of low vigour on the 6th day.The results showed that the ability of nutrition supply controlled the seed germination, and the endopeptidase played an important role.It was considered that the aging seed syntheses a new endopeptidase isoenzyme in order to accelerate the arachin degradation during seed germination.