Masters Theses

Date of Award

6-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Botany

Major Professor

Leslie G. Hickok

Committee Members

O.J. Schwarz, E.E. Schilling

Abstract

A study was undertaken to characterize the response of two homozygous strains, Hl-n and 176D-4-n, of Ceratopteris richardii (L.) Brongn. to the pheremone antheridiogen, and to determine the genetic basis of this response. Antheridiogen is a readily diffusable substance, produced by the gametophytes of some ferns, which induces undifferentiated gametophytes to produce antheridia (male gametangia). For experimental purposes, antheridiogen was obtained from a crude aqueous filtrate (CAP) of medium which had supported older cultures. This filtrate was used as an external source of antheridiogen in subsequent experiments.

Dose responses to the various concentrations of CAP were measured by determining the percentage of male (exclusively antheridiate) gametophytes in cultures. Other experiments investigated the response of cultures to internally produced antheridiogen and the way in which this effect varied with different gametophyte densities. Results showed that the two parental strains differed greatly in their response to antheridiogen over the entire range of CAP concentrations and densities at which they were studied. The effect of antheridiogen on area and antheridia number for hermaphroditic gametophytes was also determined for different CAP concentrations. A possible trend toward decreasing gametophyte area with increasing CAP concentrations was observed for both strains.

Analysis of spore germination rates for both strains on both plain and CAP supplemented media indicated that germination rates were not affected by the presence of CAP. Germination rates were not significantly different for the two strains. Analysis of the genetic basis of the antheridiogen response was accomplished by studies of reciprocal hybrids of Hl-n and 176D-4-n and subsequent P2 generations. Spores from a total of 100 P2 individuals were sown on CAP supplemented medium to determine their response type and to test for segregation from the PI hybrids. Segregation patterns among the P2's indicated two possible modes of inheritance; one in which response is mediated by two linked genes and another in which two linked genes and a single unlinked gene are responsible. Because either model could account for the responses of the P2's, both are presented and several ways in which they could be distinguished are discussed.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS