Biomedical subjects

G H Egley

Publications and source records attributed to G H Egley.

5 recordsLinked to original sources

PubMed1983

Techniques for preparing seeds with water-impermeable coats for light and electron microscopy.

An improved method for fixing and embedding seeds with impermeable coats for microscopic study has been developed. Entry portals are cut into seed coats to permit better penetration of fixative. This makes it possible to obtain semithin sections of whole seeds for light microscopy and thin sections of selected areas for electron microscopy. Seed tissues may thereby be studied relative to their position in the seed and to surrounding tissues. This permits studies of inhibition and developmental morphology of seeds in histological and cytological detail previously possible only with soft dissected seeds.

Fixatives↗

PubMed1981

Phase-sequence of redroot pigweed seed germination responses to ethylene and other stimuli.

Phase-sequence studies showed that light, ethylene, and high temperature each enhanced germination of redroot pigweed (Amaranthus retroflexus L.) seeds when given during the first 24 hours of seed imbibition. Responses were maximal during the first 12 hours. After 48 hours all three stimuli given together caused 75% germination but each alone was ineffective. The main influence of water potential on seed germination occurred at about 24 hours, but the influence of CO(2) extended into the second and third days. Germination was reduced by water stress (-4 bars) or CO(2)-free air, but ethylene reversed the reduction even when administered after several days incubation. This suggested that environmental and hormonal factors affected redroot pigweed seeds at two distinct stages in the sequence of germination events.

Journal Article↗

PubMed1980

Effects of temperature, water potential, and light on germination responses of redroot pigweed seeds to ethylene.

The responses of redroot pigweed (Amaranthus retroflexus L.) seeds to nine ethylene concentrations between 0.5 and 50 microliters per liter were assessed at different temperatures and water potentials and in either continuous white light or darkness. Under all experimental treatments, the probit-transformed percentages increased linearly with the log of the ethylene concentration. In dormant seeds, the slope of the response line was unaffected by either light or water potential but increased with decreasing temperature. Conversely, the slope increased with increasing temperature in a partially afterripened seed lot.The ethylene response threshold for germination was little affected by temperature or light, ranging from 0.2 to 0.7 microliter per liter, but decreased to less than 0.1 microliter per liter at negative water potentials. Osmotic inhibition of germination at -4 bars was largely relieved by 1 microliter per liter ethylene. Such interactions between ethylene and other environmental conditions may play an important role in the course of germination of soil-borne seeds.

Journal Article↗

PubMed1977

Model for variable light sensitivity in imbibed dark-dormant seeds.

The level of light-induced germination of the seed of common purslane (Portulaca oleracea L.) and curly dock (Rumex crispus L.) changes with dark incubation time prior to brief, low energy, red light treatment. The rate at which phytochrome-far red-absorbing form (Pfr) acts in the light-induced population of seeds was measured by quantitating per cent reversals of the red light effect with saturating far red light exposures at successive times after the red light exposure. A linear positive correlation was found between this rate and the final germination level. These results are compatible with a model involving changing levels, during dark incubation, of a component with which Pfr interacts. In this model, germination is initiated after attainment of a certain level of interaction between Pfr and this component. These findings also support the view that the Pfr to Pr decay rate constant and total phytochrome level are stable during dark incubation.

Journal Article↗

PubMed1975

Polysome Formation in Light-sensitive Common Purslane Seeds.

Common purslane (Portulaca oleracea L.) seeds show light-controlled dormancy. Ribosome profiles from dark-incubated seeds consist of 22 to 26% polysomes. Light induces germination and stimulates polysome formation during the 12-hour lag period preceding radicle protrusion. Polysome levels increase to 29, 35, and 41% with exposure to 3, 6, and 9 hours of light, respectively. Although polysomes form on imbibition in the dark, 6 hours of light stimulates a significant increase in polysome formation which is probably related to early stages of radicle elongation.

Journal Article↗