Abstract

Previous research has shown that polyembryony occurs in many species of the Ulmaceae. The purpose of this study was to determine the method of multiple embryo formation in netleaf hackberry, Celtis reticulata Torr. Collections of specimens were made throughout a two-year period. Collections were begun in early spring while the trees were still in the bud state. Collections were continued regularly throughout the growing season. The collections were preserved in FAA solution and were prepared for microscopic examination as follows: (1) The tertiary butyl paraffin method was used for dehydrating and embedding. (2) Sectioning was done on a rotary microtome at 7-20 microns. (3) Staining of the slides was accomplished by Conant's Quadruple. Examination of the slides reveals at least two, and possibly four, ways by which polyembryony may occur in C. reticulata. The most frequent method of multiple embryo development appears to be the development of an extra egg-like cell--probably a synergid--in the embryo, sac. Some slides show the egg-like cell after it has begun to develop into an embryo. The splitting of the zygotic embryo was observed on the slides and supported by germination studies in which double epicotyls were found on a single hypocotyl. Suspensor budding appears to be a means of multiple embryo formation, but the possibility of faulty interpreation of the sections, due to the plane in which they were cut, could discount this theory. Nucellar budding is also a possible means of multiple embryo development. However, here again the possibility exists that faulty sectioning of the material occurred. While the slides appear to show embryos being formed along the nucellar layer, these embryos could be of synergid origin. If nucellar budding does actually occur, it would have great genetic and evolutionary significance. Seed germination studies reveal a high percentage (20%) of multiple seedlings. It is also noted that frequently a seed will abort a few weeks after pollination. The reason for this abortion is unknown, but the author speculates that this is due to embryo degeneration. The possibility of a growth-stimulating substance being injected into the plant by the Psyllid which parasitizes C. reticulata is, the author believes, a plausible theory worthy of further study.

Degree

MS

College and Department

Plant and Wildlife Sciences

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

1968-08-01

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/Letd414

Keywords

Hackberry; Puddings; Shrubs

Language

English

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