Publication Date


Document Type


First Advisor

McIlrath, Wayne

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Plants; Effect of light on


It has been shown that certain monocarpic plants exhibit photoinductive senescence even though prevented from undergoing reproductive development. This study was undertaken to determine whether photoinductive senescence could be demonstrated for the cotyledons of such plants. Species selected for this study included the short-day species morning glory (Pharbitis nil. Chois, var. Scarlett O’Hara) and cocklebur (Xanthium strumarium L., Chicago strain), long-day species spinach (Spinacia oleracea L. var. Bloomsdale Long Standing) and radish (Raphanus sativa L. var. Scarlet Globe Short Top), and day-neutral species tomato (Lycopersicon esculantum Mill. var. Marglobe) and sunflower (Helianthus annuus L. var. Mammoth Russian). Debudded and intact soil grown plants were exposed to daylengths of 8, 10, 12, 14, 16 and 18 hours in the greenhouse and photoperiod chambers. The cotyledons of intact plants of a given species died at about the same time irrespective of photoperiod. The same held true for the cotyledons of debudded plants. The senescence of cotyledons on cocklebur (Xanthium strumarium L., Chicago strain) and morning glory (Pharbitis nil. Chois, var. Scarlett O’Hara) plants grown in and cultured in controlled environment chambers under floral inductive (10 hours) and non-inductive (10 hour interrupted) photoperiods, however, was somewhat different. As in the greenhouse soil-grown plants, the cotyledons of Xanthium plants died at about the same time in the two photoperiods. Those on morning glory showed a statistically significant delay in senescence when subjected to a non-inductive daylength. The possible reason for this difference between the two species is discussed.


Includes bibliographical references.


22 pages




Northern Illinois University

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