Abstract:The study of ecohydrological functions of a Pinm massoniana,forest with anthropogenic disturbance was carried out in Dinghushan Biosphere Reserve, Guangdong Province, during 1997-1999. Mean annual rainfall in this pine forest was 2 209.9 mm, with 83.8%-84.5% of rainfall in spring and summer, and only 15.5%-16.2% of rainfall in autumn and winter. Of the rainfall on forest canopy, throughfall comprised 82.7%, canopy interception 17.2%, and stemflow 0.15%. There was 34% of the rainfall as runoff, and the remainder evapo-transpired． Canopy interception decreased with increase in rainfall, but such decrease was lowered with the increasing rainfal1．Similar feature was observed for stem flow．Stem flow of individual tree showed linear relation with diameter breast height and with stem height under branch(p<0.01)，but did not relate with the size of forest canopy．Runoff appeared only during April to October，with mean annual runof rate 0．34．

Abstract:Biomass production and productivity of a Sassafras t.zumu forest were measured by models of allometry method in Jianyang Shufang Forest Farm of Fujiang Province. The forest was naturally regenerated by dominant S. tzumu after final cutting of Cunninghamia lancenlata plantation at about 20 year's succession with density of S. tzumu trees ca. 480 individuals per ha. The results showed that mean total biomass production and mean annual productivity of S. tzumu trees were 58 693 kg hm^-2 and 4 259 kg hm^-2, respectively．Vertical distribution of biomass indicated that most biomass was accumulated below middle height of trees．In accordance with the diameter class distribution of biomass，the maximum biomass appeared at trees with 20 cm dbh．This research is useful for broad-leaved forest planting．

Abstract:Fine roots were measured by soil core sampler in a mixed plantation of 27-year-old Cunninghamia lanceolata (C) and Tsoogiodeudron odorum (T) in Fujian Province. Fine root density of C at interrow between C and T was lower by 8.5% than that between C and C, but fine root denstiy of T and total fine root density were higher by 152.09% and 10.43%, respectively. High density of living fine roots with different thickness of C in mixed plantation appeared at 5-10 cm soil depth, whereas that of T at 0-10 cm. Compared to mixed plantation，living fine root density in pure C plantation appeared at 10-30 cm of soil depth．The distribution of dead fine roots had the same pattern．In mixed plantation， upward trend of soil layer with maximum fine roots of C was obvious， showing that mixed plantation had an advantage over pure plantation in nutrient absorption．

Abstract:Species diversity, ecological distribution, hosts and floristic elements of Meliolales in China were studied. 341 species and varieties (comprising 15% of the world species), belonging to 7 genera were reported. Among them, dominant genera are Melioln (239 species and varieties), Asteridella (54) and Appendicidella (22). Species of Meliolales in China are distributed mainly in tropical and subtropical areas, and 76.8% of the host plants are of tropical elements. Geographical elements of Meliolales speciesin China can be included in 11 areal types, viz.cosmopolitan elements (0.3%), pantropical (7.3%), tropical Asia and tropical America (9.1%), Old World tropical (0.3%), tropical Asia and tropical Africa (16.1%), tropical Asia (34.0%), north temperate (0.6%),East Asia and North America (0.3%),East Asia (1.7%), Endemic to China (28.2%). Thus, tropical elements of mycoflora in China comprise 68.9% of the total, and edemic to China species amount to 28.2%. The distribution of genera of Meliolales in China, and the numbers of species or varieties parasitized on what host plant families is tabulated.

Abstract:Michelia elliptilimba B. L. Chen et Nooteboom is reduced to a synonym of M. sphaerantha C. Y. Wu ex Law et Y. F. Wu. M. caloptila Law et Y. F. Wu and M. septipetala Z. L. Nong are reduced to synonyms of M. fujianensia Q. F. Zheng, and M. laevifolia Law et Y. F. Wu and M. yunnanensis subsp. glabrifolia Y. K. Li et J. F. Zuo, to synonyms of M. yunnanensis Franch. ex Finet et Gagnep., while M. foveolata var. xian.gnanensis C. L. Peng et L. H. Yan and M. hunanensis C. L. Peng et L. H. Yan are regarded as synonyms of M．foveolata Merr．ex Dandy and M．cavaleriei Finet et Gagnep，respectively．The identities of Magnolia odoratissima Law et R．Z．Zhou and Michelia sphaerantha C．Y．W u ex Law et Y．F. Wu are clarified．

Abstract:This paper reports 2 genera. Pleocnemia Presl (Aspidiaceae) and Lornagramma J. Sm. (Lomariopsidaceae), of pteridophytes recently re-discovered in Hong Kong. The specimens of Pleocnemia winitii Holtt.. P. conjugate (Bl.) Presl, and Lomagramma matthewii (Ching) Holtt. from Hong Kong, and related references were reviewed. The closely related species found in China were revised taxonomically. Pleocnemia hamata Ching et Chu H. Wang, and P. kwangsiensis Ching et Chu H. Wang are regarded as two new synonyms of P． winitii Holtt．In addition，after observation on Lomagrcanmct matthewii (Ching) Holtt. for a long period，we consider that Holttum’s description on morphology of rachis apex of this species is exact． The re-discovery of Pleocnemia Presl and Lomagramma J．Sm ．in Hong Kong is significant for the study of phytogeography of pteridophytes in South China． It is recommended to list them in rare and endangered ferns in Hong Kong as they are quite rare locally.

Abstract:Floral development of Blyxa japonica (Miq)Maxim, ex Asch. et Gürk(Hydorcharitaceae) has been observed under scanning electron microscope (SEM). The sepal primordia first initiate on radii verticillately. A whorl of alternisepalous petal primordia forms nearly simultaneously. Three antisepalous stamen primordia initiate verticillately, alternating with petal primordia. At the base of petal primordia, three antipetalous gynoecial primordia appear verticillately. Compared with other genera in the family, the flower of Blyxa japonica shows many primitive characteristics，such as bisexual，actinomorphic an d numerous ovules，whereas the number of floral organs is fixed as 3 shows its interm ediate evolutionary leve1． Floral organongensis initiating verticillately and inferior ovary indicate advanced characteristics of Hydrocharitaceae in Alismatidae.

Abstract:The stems and blades of lawn grasses, Zoysia tenuifolia Willd. ex Trin., Paspalum vaginatum Sw. and Cynodon dactylon (L.) Pers., were anatomically studied. The structures of grass stems and blades showed close relation to the grass drought and trampling resistances, and elasticity. Among the three grasses, Z. tenuifolia was the best in drought resistance, trampling resistance and elasticity in terms of the epidermis, bulliform cells, bundle sheath, sclerenchyma of leaf, and the fibrous girdle of stem; C．dactylon was better in drought resistance，but poorer in tram pling resistance and elasticity：whereas P．vaginzttum was the worst in these characters．

Abstract:Male sterile rice varieties IR66707A and IR69700A from IRRI contain cytoplasm of Oryza perennis and O. glumaepatula, respectively. Their sterility can only be maintained but cannot be restored, so they are cytoplasmic male sterile. Among the total 136 somaclones, three types of mutants were obtained by somatic cell culturing from the two male sterile lines, and their F1 progenies derived from crossing with normal cultivars. They were fertile mutants (type Ⅰ), various male sterile mutants (type Ⅱ ), and female sterile mutants(type III)．In type I，among 18 clones (R₁) from the donors of hybrid F₁，two were fertile．The fertility in the R₂ generation was segregated and the ratio of fertility to sterility was 3：1， showing that the mutants were controlled by a single dominant gene． In Type II， the sterility of some clones could be restored which were quite different from the donors of male sterile lines． Among these clones a part of the sterility could not be maintained but could be converted to be fertile as the environment changed，another part was inconvertible，but restorable and incompletely maintainable，although some segregation appeared．Also in type Ⅱ，the sterility of some clones could not be restored， and were similar to the donors． It is suggested that the convertible mutants could serve as dual-purpose genic male-sterile lines in rice breeding．Type Ⅲ was completely sterile，both for male and female．

Abstract:Forty-eight rice sheath blight strains (Rhizoctonia solani AG 1-IA) from seven counties in Guangdong province were analyzed for genetic diversity using RAPD technique. Ninety-eight RAPD bands were amplified with 10 arbitrary decamer primers, among which 89.9% were polymorphic. Analysis of amplified polymorphic DNA fragments showed that the Nei's similarity coefficients of isolates were 0.560 -0.949. The tested isolates could be classified into 5 RAPD groups (A, B, C, D, and E), and most of the isolates from the same area clustered in a same group by using UPGMA analyses. THe virulence test carried out in greenhouse showed that all isolates were virulent to rice variety Tetep, the disease index (DI) ranged from 0.73 to 18.7, the mean DI was 5.24, and the virulence variation was significant(α=0.05).The analysis showed that there existed abundant genetic diverdsity among rice sheath blight fungal popilations, and the genetic variation was very signficiant in R. solani AG 1- ⅠA population from different counties in Guangdong province (F_{ST=0.579). The RAPD clustering groups had obvious correlation with geographical origin, but the virulence variation had no significant correlation with geographical origin and with RAPD groups.}

Abstract:Two cultivars of nectarine, nonmelting-flesh 'Arm King' and melting-flesh 'Qinguang1, were used to investigate the enzyme activities in relation to fruit softening after harvest. Invertase and amylase activities were high during the rapid loss stage of fruit firmness, then decreased gradually during further softening. However, cellulase and polygalacturonase showed low activities, but increased significantly at climacteric stage. The activity of pectin methylesterase was low and showed little change. The activity of pectin methylesterase was low and showed little change.Activities of all these enzymes were higher in‘Oinguang’than in ‘Arm King’.

Abstract:The seeds and embryos of Zea mays L. cv. Yuedan 9117 were used to determine the acquisition of desiccation tolerance and germinability during maize seed development. Physiological maturity of seeds was at 42 days after pollination (DAP). The embryos obtained germinability during 14-21 DAP, and the desiccation tolerance of embryos was obtained during 25-28 DAP, desiccation tolerance still being strengthened after 28 DAP. The changes in electrolyte leakage rate of seeds and embryos during development of maize seeds might suggest that there was a close relationship among desiccation tolerance，membran e development， and protection of membrane injury．Desiccation is beneficial to germ ination of seeds and embryos during the development of maize．

Abstract:Oxalate content in the roots, stem and leaves of hydroponically-cultured tobacco plants was very significantly correlated. When plant leaves were fed with ¹⁴CO₂, a large amount of ¹⁴C-oxalate rapidly emerged in the leaves, followed in the stem, and then in the roots, with a lag about one hour. The result indicated that oxalate might be rapidly formed in the leaves through photosynthetic CO₂ fixation, and part of it was then transported to the roots through the stem.

Abstract:This review decribes recent advances in effective biological control of postharvest diseases of fruits and vegetables , including application of antagonistic microorganisms, induction of disease resistance, using natural plant products, and genetic engineering for improving plant resistance to pathogens.