Author

Campbell

Date of Award

7-1960

Degree Name

Master of Arts

Department

Biological Sciences

First Advisor

Dr. Leo C. Vander Beek

Second Advisor

Dr. Thane S. Robinson

Third Advisor

Dr. William C. Van Deventer

Access Setting

Masters Thesis-Open Access

Abstract

Introduction

The propagation of plants by seeds is often made difficult by dormancy in seeds. A dormant seed is one that will not germinate when it is exposed to conditions favorable for germination. Such seeds will begin growth, however, after they have been subjected to the proper after-ripening conditions. Therefore, the grower must wait several months in many cases before his seeds will germinate. Since it is often desirable to determine the viability of seeds at an early date, seed dormancy has presented a major problem to the farmer. The testing of dormant seeds (4,6,44,56,64,) is widely practiced and rules for seed testing have been formulated (55).

Crocker (21) listed the following factors as causes of seed dormancy: (1) a rudimentary embryo; (2) inhibition of water absorption by the seed coat; (3) mechanical resistance of enclosing structure; (4) interference with oxygen and carbon dioxide diffusion by the seed coat; (5) dormancy of the embryo or part of it; (6) a combination of the above factors; (7) secondary dormancy. Other investigators have added to this list inhibiting substances in the seed coat and in the embryo (1,2,11,14,18,36,50,51,57).

A great many seeds may be after-ripened by a low temperature treatment (22,23,33,34,40,45). The length of treatment may vary with the amount of incident light for seeds that are light-sensitive (12,37,42,63,66,71,72), although the effect of light on other seeds is not temperature-dependent (3,29,62,67). The red portion of the solar spectrum has the greatest effect on germination (3,12,75,76). Studies indicate that light initiates or inhibits germination by affecting compounds in the seed (62,67). Still other seeds will germinate only after being stored for various periods at a relatively high temperature (58,68).

Many of the chemical changes that take place during the after-ripening period (30,34,60,72,73) are reversible and secondary dormancy can occur if seeds are subjected to unfavorable conditions (10,15,21,27,38,63).

The studies reported here concern the effect of the seed coat on the germination of Rhodotypos kerrioides (jet bead).

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