Effects of Reduced Irradiance on the Biology of Eastern Black Nightshade (Solanum Ptycanthum)
Myers, Randy Allen
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https://hdl.handle.net/2142/71625
Description
Title
Effects of Reduced Irradiance on the Biology of Eastern Black Nightshade (Solanum Ptycanthum)
Author(s)
Myers, Randy Allen
Issue Date
1986
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Abstract
Eastern black nightshade (Solanum ptycanthum Dun.) is problematic in soybean Glycine max (L.) Merr. fields because of its unique ability to survive in the shaded environment under the soybean canopy. These studies were conducted to investigate the effects of shade and soybean interference on plant growth and development, berry production, and seed formation of eastern black nightshade. Increasing interference from soybeans by decreasing the soybean row width, delaying emergence until after the soybean canopy had closed, and restricting escapes to the intrarow spaces reduced the plant growth and berry production of this weed. The largest eastern black nightshade plants that were harvested were positioned between the 75-cm soybean rows and emerged with the soybean seedlings. They produced 264 berries and a plant dry weight of 43 g. The smallest plants that were harvested had a plant dry weight of less than one gram and less than one berry per plant. These plants were positioned in the 32.5-cm soybean rows and emerged 6 weeks after the soybeans had emerged. In a study to determine the effects of shade alone, in the absence of other interference factors, eastern black nightshade plant growth and berry production was also reduced by increasing levels of artificially produced shade and decreasing the length of the growing season that these plants were given at these shade levels. Plants grown without shade had dry weights of 243 g with almost 6000 berries if given a 20 week growing season, but if grown in 6% of full solar radiation plants produced only 23 berries with a dry weight of 3g. High levels of shade had the added effect of slowing the rate of increase of seed weight as the seeds developed in the eastern black nightshade berries. This increased the amount of time after anthesis needed for viable seed production. Adaptation of eastern black nightshade to increased shade was compared with other species (common lambsquarters (Chenopodium album L.), velvetleaf (Abutilon theophrasti Medik.), tumble pigweed (Amaranthus albus L.) and soybean) to determine the characteristics that eastern black nightshade possesses that enable it to be shade-tolerant. For plants grown at the lowest level of available photosynthetic photon flux density, eastern black nightshade had the lowest respiration rate, the lowest root-to-shoot ratio, the lowest leaf density, and the highest leaf area ratio, indicating that it is the most shade-tolerant of the species studied.
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