|其他摘要||The seed dormancy, germination, storage behaviour, storage conditions, plant in vitro micropropagation and in vitro preservation of several Magnoliaceous plant species were studied in the present thesis. The seed dormancy types, breaking dormancy methods, storage behavior and appropriate storage conditions of Manglietia cuclouxii, Magnolia wilsonii, Michelia calcicola, M. champaca, M. sphaerantha and M. yunnanensis were tested and confirmed through seed biological approaches. Magnolia biondii, M. odoratissima, Michelia champaca, M. chapensis, M. floribunda and M. sphaerantha plants were cultured and conserved in vitro successfully. And an effective in vitro preservation method was developed.
1. Seed dormancy types of six Magnoliaceous species seeds
Our research revealed that seeds of Michelia champaca were with morphological dormancy. Gibberellic acid could stimulate seeds germination of M. champaca. Seeds of Manglietia cuclouxii, Michelia calcicola, M. sphaerantha and M. yunnanensis belonged to the type of intermediate complex morphorphysiological dormancy. After-ripening, cold stratification and GA could break morphophysiological dormancy of seeds of above four species. The physiological dormancy among morphophysiological dormancy could be nondeep physiological dormancy. Seeds of Magnolia wilsonii had intermediate complex morphophysiological dormancy. After-ripening could not break dormancy of seeds of M. wilsonii, however, could shorten cold stratification time. The physiological dormancy of M. wilsonii could be intermediate physiological dormancy.
Seeds of Manglietia cuclouxii and Michelia yunnanensis could have dormancy cycles, which was firstly found in intermediate morphophysiological dormancy.
2. Seed dormancy broken menthods of six Magnoliaceous species
Cold stratification and GA could effectively overcome seeds dormancy of six Magnoliaceous species. Cold stratification time was different among six species. Warm stratification did not affect on seeds dormancy of six Magnoliaceous species. Washing and dipping in 4℃, and KNO3 could only break seed dormancy of Michelia sphaerantha.
After-ripening could break seed dormancy of seeds of Manglietia cuclouxii, Michelia calcicola, M. sphaerantha and M. yunnanensis. After-ripening for 100d in 4
℃, seeds dormancy of Magnolia wilsonii were not overcome.
3. Seed storage behaviour and appropriate storage conditions of six Magnoliaceous species
Seeds of Manglietia cuclouxii, Magnolia wilsonii, Michelia calcicola, M. champaca, M. sphaerantha and M. yunnanensis were desiccated in different time. Seeds desiccation tolerance and storage condition (at 4℃ and -20℃ for 2-3 months) were tested through seed germination percentage. Seeds of Manglietia cuclouxii and Michelia yunnanensis could be intermediate seeds, which could survive partially at -20℃. Seeds of Magnolia wilsonii could be intermediate seeds which died at -20℃. Seeds of Michelia calcicola, M. champaca and M. sphaerantha could be low recalcitrant types which could tolerate low temperature above 0℃.
The research showed seeds of six Magnoliaceous species could tolerate low temperature above 0℃. Seeds storaged for 2-3 months at 4℃ retained high viability. Therefore, seeds of six Magnoliaceous species are adapt to be storaged at 4℃. Fresh seeds of recalcitrant seeds (Michelia calcicola, M. champaca and M. sphaerantha) could be storaged at 4℃. Intermediate seeds (Manglietia cuclouxii and Michelia yunnanensis) could be desiccated to 10%-15% to be storaged at 4℃. Seeds could be storaged in moist medium in low temperature (4℃).
4. In vitro culture and preservation of six Magnoliaceous species
Young seedlings of Magnolia biondii, M. odoratissima, and Michelia champaca, M. chapensis, M. floribunda and M. sphaerantha were cultured in vitro. Axillary shoot development was induct and multiplied. The research found low concentration of phytohormenes was favorable for growth and multiplication of shoots. L-Ascorbic acid could reduce damages of browning. In this research, explants induction and shoots multiplication were not difficult for young explants. However, vitrification, browning and broken callus were still the main problems in Magnoliaceae microprapogation.
Three types of medium without hormones were chosen for in vitro preservation of six Magnoliaceous species. Active carbon could prevent browning of shoots. In three types of in vitro preservation medium, plants grew slowly but healthily and survived for half a year, and even for one year or longer.
Our studies revealed: low recalcitrant seeds of Michelia champaca belonged to morphological dormancy; low recalcitrant seeds Michelia calcicola and Michelia sphaerantha belonged to intermediate complex morphophysiological dormancy; intermediate seeds of Manglietia cuclouxii, Magnolia wilsonii and Michelia yunnanensis belonged to intermediate complex morphophysiological dormancy. The effective preservation methods of Magnoliaceous resources were storaging seeds at low temperature in dry or moist environment. And the medium with free phytohormenes and active carbon could effectively preserve Magnoliaceous regenerated plants in vitro.|