Degree Type

Dissertation

Date of Award

1988

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

Micheal D. K. Owen

Abstract

Woolly cupgrass seeds at physiological maturity are dormant. The purpose of these studies was to evaluate the seed production capability of woolly cupgrass, seed dormancy factors, and the factors that influence the germination and emergence of woolly cupgrass. Planting of woolly cupgrass later than the month of May greatly reduced woolly cupgrass yield by reducing the production of tillers, panicles, seed numbers/panicle, the number of seeds/raceme, and plant dry weight;The rate of imbibition between dormant and nondormant seeds was the same. Dehulling promoted the germination of dormant seeds by 60%. Oxygen levels above atmospheric concentration completely terminated the dormancy of partly dehulled seeds. The oxygen uptake of dehulled dormant and intact nondormant seeds was significantly greater than that of intact dormant woolly cupgrass seeds. Seed leaching did not promote the germination of intact dormant seeds. Leachate from dormant seeds did not inhibit the germination of nondormant seeds. Excised embryos from dormant seeds germinated under laboratory conditions. Prechilling dehulled seeds for 2 weeks and intact dormant seeds for 6 weeks at 5 C, completely terminated the dormancy of woolly cupgrass. In the field, the termination of seed dormancy was completed by the first week of December. These results suggest that woolly cupgrass seeds possess two types of dormancy. Caryopses dormancy which may be imposed by the seed coat or the endosperm can be terminated by prechilling or by oxygen levels higher than atmospheric concentration. The second type of dormancy is imposed by the seed hulls which limit oxygen diffusion to the embryo;Nondormant woolly cupgrass seeds are not photoblastic. The optimum temperature range for woolly cupgrass seed germination was between 20 and 38 C. Any microenvironment with 4% oxygen concentration can promote the germination of nondormant woolly cupgrass seeds. The optimum seedling emergence depth for woolly cupgrass was between 1 and 4 cm.

DOI

https://doi.org/10.31274/rtd-180813-8850

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Iliya A. Bello

Language

en

Proquest ID

AAI8909126

File Format

application/pdf

File Size

163 pages

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