Abstract:Of the 388 rare and endangered plant taxa included in Volume one of the ChinaPlant Red Data Book-Rare and Endangered Plants, 14 species have been recorded inHong Kong Special Administrative Region. Of these, 2 are pteridophytes, 2 aregymnosperms and 10 are angiosperms. Most of these 14 species are also distributed inGuangdong Province with one exception namely Ophioglossum thermale. Two species,Aquilaria sinensis and Artocarpus hypargyreus, which are included in the China Plant RedData Book and classified as vulnerable，are relatively common in Hong Kong． The distribution and conservation of these 1 4 nationally rare and endangered plant species in Hong Kong are described．

Abstract:Species composition and structure of the Erythrophleum fordii community wereinvestigated in December 1995 in Dinghushan Biosphere Reserve. The results showed that91 species in 78 genera and 49 families of vascular plants were found in a plot of 1 600 m2,and most plants were of tropical genera. The physiognomy of the community was evergreenall the year round. The life form in the community was dominated by phanerophytes, and theleaf form being dominated by plants with simple leaf and mesophylls for most trees. The stratification was obvious，and the trees could be divided into three layers Species diversity and complicated structure in the community reflected the climatic conditions of warmer temperature and higher humidity in southern subtropics． The importance value of Erythrophleum fordii population was higher than that of other population in the studied community， which was named as Erythrophleum fordii community．Although legumes are abundant in low subtropical forests，however，the comunities with legumes dominated are hardly to be found elsewhere．

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Abstract:Two species, namely Clematis xinhuiensis R. J. Wang and C. zhejiangensis R. J.Wang, and one variety, namely C. henryi Oliv. var. trifolia R. J. Wang, are described as newin China. An additional morphological description of species C. liboensis Z. R. Xu is given.

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Abstract:Based on the study of specimens and type photographs of Buxaceae from China,Buxus cephalantha Levl. et Vant. is regarded as a new synonym of B. harlandii Hance.Four taxa, viz. B. microphylla Sieb. et Zucc. var. prostrata W. W. Smith, B. sinica (Rehd. etWils.) Cheng ex M. Cheng var. vacciniifolia M. Cheng, B. sinica (Rehd. et Wils.) Cheng exM. Cheng var. pumila M. Cheng and B. rugulosa Hatusima var. prostrata (W. W. Smith)M. Cheng, are regarded as new synonyms of B. rugulosa Hatusima, while B. cephalantha Levl. et Vant. var. shantouensis M. cheng and Sarcococca orientalis C. Y. Wu ex M. Cheng are new synonyms of B. stenophylla Hance and S. longipetiolata M. Cheng., respectively. Buxus myrica Levl. is a new record to Hubei ,Jiangxi and Fujian , B. rugulosa Hatusima a new record to Guangxi and Fujian, and Sarcococca hookeriana Baill. var. digyna Franch. a new record to Guizhou and Guangxi.

Abstract:Seed coat patterns of seven species of Cercis were studied by using scanningelectron microscope. Two groups of species were recognized by spermodermic characters.The first group includes a single species, C chingii. The second group includes all otherspecies studied.

Abstract:Seed morphology and germination, seedling morphology and biomass of 24 treespecies in the lower subtropical forest of China were studied comparatively in light anddark conditions on expanded perlite as germination and growth medium. Seed morphologyand seed mass were related with species of different successional stages of the forest andwith species from different families. Percentage of germination was obviously differentamong various species. Heavier seeds had higher percentages. Seeds from pulpy fruit usually showed significantly later germination． Light and dark conditions did not significantly affect germination percentage and germination speed of the species. Seedling height was positively correlated with seed weight. The correlation betwen seed weight and seedling height semed to be more obvious under light treatment． Dark condition caused the stem etiolation and limited the growth of root of the early seral(successiona1)species．However it was not so obvious for late seral species．Seedlings of about half of the species had higher shoot biomass than root biomass in both light and dark conditions. Shoot and root biomass allocation was related with different families，and with different seral stages of the species．It was also affected by light and dark conditions．Seed weight appeared not to affect the biomass ratio of shoot to root in seedlings． Root and leaf biomass allocation were related with species．Biomass of the seedlings was positively related with seed weight． Relative growth rate (RGR) of the seedlings without nutrient supply was quite different among the species．Higher RGR was found in the mid seral species．Matter utilization efficiency (MUE) of the seedling from seed was obviously negatively related with seed weight，and appeared not to be related with seral stages of the species．

Abstract:Under drought condition, the drought-tolerant riee cultivar "Xiangzhongxian No.2" showed lower relative plasmalemma permeability and less reduction in chlorophyllcontent as compared with drought-sensitive cultivar "Xiangzaoxian No. 12" , whichindicated that the drought-tolerant cultivar was less demaged by drought stress. Ascorbate-peroxidase (AsA-POD) activity decreased in both cultivars, but less decreased in drought-tolerant one. The glutathione reductase (GR) activity increased at the beginning of drought in drought-tolerant cultivar，but that did not change obviously in drought-sensitive one．The results also showed that GR activity could be induced by paraquat(0.01 mmol／L)and H₂0₂(0.1 mmol／L)in drought-tolerant cultivar，but they had no effects on drought_sensitive one，which indicated that the increase of GR activity in drought-tolerant cultivar under drought stress might result from the induction by oxidative stress．In addition，the contents of ascorbate (AsA) and reduced glutathione (GSH) showed a tendency of being increased at first，then decreased in both cultivars，but with greater increase in the drought-tolerant cultivar．The results suggested that drought_tolerant cultivar had better protection system in chloroplasts against drought stress than the drought-sensitive cultivar.

Abstract:Fruit development of litchi (Litchi chinensis Sonn.) and pigment change in skin ofcultivars ‘Feizixiao' and‘Nuomici' were studied. The fruit growth showed a sigmoidalpattern: the duration of the first phase in fruit growth of‘Nuomici' was 7 - 10 days longerthan that of‘Feizixiao '. A peak of anthocyanin synthesis appeared at the first and secondphases of fruit growth in both cultivars. The total anthocyanin level of ‘Feizixiao' wasobviously lower than that of ' Nuomici' . In 'Feizixiao' and ‘Nuomici' ，no obvious correlation was found between anthocyanin and chlorophyll co ntents． But the rapid decline in chlorophyll coincided with substantial increase in anthocyanin concentrations at late phase of fruit development. There was no clear correlation between the changes in anthocyanin synthesis and in phenylalanine ammonia lyase (PAL)activity．

Abstract:The optimal culture conditions of the growth of Cymbidium sinense protocormsinduced from embryo were studied. The results showed that MS was the best basal mediumfor C. sinense protocorm growth and organogenesis. Treatment of 0.5 mg L^-1 NAA incombination with 1.0 mg L^-1 BA was most satisfactory for protocorm growth. When 1%sucrose and 0.1% activated carbon were added to the basal medium, a superior growth ofprotocorms was observed. Highest increase of the fresh weight of protocorms was at PH 5.0, Protocorms grew well under l5.5μmol m^-2s^-1 light intensity for 16 hours per day．Combined treatment with all optimal single factors mentioned above showed that the fresh weight of protocorms was 46％ higher than that of the control．As for the in crease of proliferation coeficient，dividing the protocorms by hands gave good result in cutting Inanner．

Abstract:High, medium and low vigour maize (Zea mays L.) seeds were obtained fromdifferent aging treatments. The content of embryo storage proteins in high vigour seedsdeclined more rapidly than that in medium and low vigour seeds during germination.Protein synthesis in high vigour seeds at 24 hours after imbibition was higher than that inaging seeds.

Abstract:Some experiments had proved that 6-methoxy-2-benzoxazolinone (MBOA) was themain substance in phototropism of maize coleoptile. The physiological effects of MBOAwere studied by using the methods of bioassay and HPLC. The results showed that: 1. Thegrowth rate of hypocotyl of cress and cockscomb were inhibited obviously when treatedwith the substance excreted from maize coleoptile. The main component of the substancewas MBOA. 2. Antagonistic effects was found when the maize coleoptiles were treated with IAA and MBOA in combination．3．When an agar piece containing MBOA was placed on unilateral side of coleoptile with tip exised，the coleoptile could bend to growth．4 The content of MBOA increased when maize coleoptile was injured．It was shown that MBOA was the natural inhibitor which played important function in inducing plant phototropism as well as in protection against injury. It can be concluded that MBOA is a substance that antagonizes IAA and inhibits the plant growth．

Abstract:Primary somatic embryogenesis could be directly induced from immature leaves ofcassava (Manihot esculenta Crantz) on the MS solidified medium supplemented with higherconcentration of 2,4-D (1-16 mg L^-1) or NAA (40 mg L^-1), but IBA and IAA (40 mg L^-1)could not induce it. When the somatic embryo fragments were used as explants, the needof auxin activity and concentration for the induction of secondary somatic embryogenesisdecreased. The decrease of the concentration or activity of the auxins in the induction media could enhance somatic embryogenesis and root formation，and result in the increase of plant regeneration frequency. It was observed that somatic embryos could not develop shoot meristem on the induction medium containing 4 mg L^-1 2，4-D. The experiments showed that the auxins stimulated the induction of cassava somatic embryogenesis but inhibited the development of somatic embryos and decrease plant regeneration in cassava.

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