Relationship of ovule developmental parameters to somatic embryogenesis in Cercis canadensis

Ovules of Cercis canadensis L. (Eastern Redbud) were only competent to produce somatic embryos during a discrete period of their development. This interval was characterized by relating the somatic embryogenic potential of ovules with ovule development and changes in ovule protein profiles over time. Redbud pods were collected once or twice weekly from 82—159 days post anthesis (dpa). Ovules were removed from pods, cultured on a modified SH medium, and evaluated six weeks later for the development of somatic embryos. Additional ovules were analyzed for zygotic embryo length and developmental stage, and ovule fresh weight. Somatic embryogenesis occurred when ovules where in the torpedo and cotyledonary stages of development. Zygotic embryo length was associated with somatic embryogenesis during the exponential phase of elongation; ovule fresh weight was less effective in predicting embryogenesis.

In a second study, proteins were extracted from redbud ovules, and analyzed by SDS-PAGE gel electrophoresis. Changes in intensity of six protein bands were associated with changes in the somatic embryogenic potential of the ovules over time. Protein bands weighing 32 and 36 kDa decreased significantly in intensity when ovules became competent to produce somatic embryos. The four remaining bands increased in intensity from the middle to the end of the sampling period, and this was associated with a decrease in the somatic embryogenic potential of the ovules.