Rhododendron fortunei is one of the famous ornamental flowers in China, but its water conditions for growth are less known. Effects of soil water stress on antioxidant system and lipid peroxidation in the leaves of R. fortuneiwere investigated by using 5-year old pot-cultured seedlings as experimental materials and exposing them to different levels of water stress. Twelve pots of plant seedlings with a similar growth were divided into 4 groups: no stress (control), light stress, moderate stress and heavy stress. In comparison with no stress and light water stress, moderate stress and heavy stress resulted in significant increases in the malondiadehyde (MDA) content, generating rate of superoxide anion (O2-.), proline content, peroxidase(POD) activity and membrane permeability of leaf cells and significant decreasea in glutathione(GSH) content, carotenoid content and catalase (CAT) activity. However, the content of ascorbic acid (AsA), activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) exhibited another, i.g. increased under moderate water stress, but decreased under heavy water stress. The present conclusion is that R. fortunei growth can be inhibited through enhancing lipid peroxidation under heavy water stress.
Pollen viability and the process of fertilization inClivia miniata Regel are studied by means of storing the pollen at low temperature and routine paraffinembedded sectioning technique, so as to offer some information for its cross breeding.The results are as follows: The setting percentage of fresh pollen is 35%, it declines to 22% when the pollens are kept for 70 days at -21℃, it turns to 4% when the pollens are stored for another 70 days. Two sperms have the characteristic of heteromorphism. In mature embryo sac, secondary nucleus lies in the antipodal cells end. Asynchronization, unfertilization and abortion in the process of ovule development are main reasons for low setting percentage. Fertilization and duration of each stage: Pollen grains germinate about two hours after artifical pollination, then the pollen tube prolongs in style for about 12 h. Fusion of male and female sexual cells takes place 42-50 h after pollination. The division of primary endosperm nucleus takes place 44-46 h after pollination. 6-7 days after pollination, zygote begins to devide. The dormancy stage of zygote lasts about 4-5 days.