Date of Award

Summer 1984

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Lytton J. Musselman

Committee Member

Paul W. Kirk, Jr.

Committee Member

Robert Eplee

Committee Member

James F. Matta

Committee Member

Kneeland K. Nesius

Call Number for Print

Special Collections LD4331.B46 C64


The effect of temperature on the germination of Orobanche ramosa L., branched broomrape, was investigated by dividing the physiological stages leading to germination into discrete events: pretreatment, a period when the seed becomes receptive to stimulant, and posttreatment, when stimulant application (GR-24) induces germination. Seed was pretreated and posttreated at 16 different temperature combinations. Optimal pretreatment was at 15°C and 18°C, maximum posttreatment at 18°C. Highest germination was obtained by pretreating and posttreating seed at 18°C, lowest at 24°C. The effect of different pretreatment regimes was tested. Seeds were pretreated over moist filter paper and in soil for Oto 56 days. In vitro assay showed nearly identical pretreatment effects during the first two weeks of the experiment. Germination response declined after 21 days pretreatment over paper, but remained optimal (75% or greater) with soil pretreatment. The efficacy of strigol and the strigol analogs (GR compounds) GR-7, GR-24, GR-42 and GR-60 was tested. Concentrations of 0.01 ppm to 100 ppm GR-24, 1.0 ppm to 100 ppm GR-7 and 10 ppm strigol induced maximum germination. In greenhouse studies broomrape was potted with a variety of potential host plants. Hosts included tobacco, tomato, eggplant, bell pepper, sunflower, broadbean and celery. The parasite grew to maturity on tobacco and tomato, only the underground stages were observed on other hosts.


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