Culture of isolated embryos of Pinus radiata D. Don
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Effects of nutritional factors, plant growth regulators, and physical factors on the conversion of isolated embryos into plantlets of Pinus radiata were investigated. Results showed that nutritional factors were critical to the conversion of isolated embryos into plantlets of P. radiata. The optimum medium strength was half strength of the medium consisting of modified Quoirin and Le Poivre (LP) salts (von Arnold and Eriksson 1981) and Schenk and Hildebrandt (1972) (SH) vitamins. Sucrose (3%) as well as glucose (2-3%) and fructose (2-5%) could serve as carbon sources for the conversion of isolated embryos into plantlets of P. radiata. In general, a few significant benefits were found with the addition of organic nitrogen sources tested on the performance of isolated zygotic embryos into plantlets of P. radiata. Nearly all plant growth regulators tested were not beneficial for the conversion of isolated zygotic embryos into plantlets of P. radiata, and some of them had negative effect. Only GA₃ (gibberellic acid at 0.58 μM) seemed to stimulate embryos to germinate a little bit earlier in comparison with the control. Submerging the cotyledons of the isolated embryo into the agar-gelled medium showed better growth in comparison with the control. Embryos cultured in liquid medium grew better but the germination percentage was apparently lower compared with 0.8% agar-gelled medium. liquid medium with sponge support could increase the percentage of germinated isolated embryos but the embryo growth was not comparable to the liquid medium only. The addition of PEG (polyethylene glycol) 6000 to the liquid medium seemed to increase the germination percentage and had no negative effect on the growth of isolated embryo. Light could influence embryo growth in different ways. For root growth, 16-hour photoperiod appeared to be the best, but for cotyledon development continuous light condition seemed to be the best. In continuous darkness, the hypocotyl appeared to elongate more, but the cotyledon and root did not grow well. Isolated embryos cultured on the optimum medium (LPSH2) grew well. The resulting plantlets (i.e. emblings) appeared normal, but were smaller than seedlings. Studies on biochemical changes during germination and early embling or seedling growth showed that the patterns of changes in total protein, soluble sugar, and starch content were generally different between emblings and seedlings. However, on fresh weight basis, total protein concentrations and their SDS-PAGE profiles showed that there was little difference between emblings and seedlings. Results of this study should be helpful as a basic reference for the artificial seed technology development starting from germination and plant conversion of P. Radiate somatic embryo with an artificial megagametophyte.