Author

Keith E. King

Date of Award

5-2003

Document Type

Thesis

Department

Plant Science

First Advisor

Robert Williams

Second Advisor

Raymond Faucette

Third Advisor

Paul Bartholomew

Abstract

Seedling emergence is either hypogeal or epigeal. In hypogeal emergence the cotyledons remain below the soil surface during seedling development, while in epigeal emergence the cotyledons extend above the soil surface due to elongation of the hypocotyl. Here we examine the effect of seed size, and emergence type, on seedling growth. Six legumes with variation in seed size and either epigeal or hypogeal emergence were grown under dark and light conditions. A competition study was also conducted where a hypogeal and epigeal legume were grown in combination with wheat and ryegrass. Legumes expressing epigeal emergence were cowpea (Vigna unguiculata), mung bean (Vigna radiata) and soybean (Glycine max Merr.), while Austrian winter pea (Pisurn sativum var. arvense (L.) Poir), field pea (Pisum arvense) and lentil (Lens culinaris) expressed hypogeal emergence. In the dark growth study, seed size did not have a direct effect on growth, but there was a correlation with the heavier seeded species having heavier seedlings. Soybean had the largest seedlings under both dark and light conditions. Wheat and ryegrass competition reduced both Austrian winter pea and soybean growth. However, the cool air-temperature during the study may have favored the growth of Austrian winter pea, a cool-season legume. Soybean, a warm-season legume, seedling development may have been limited by the cool-temperature. We could not separate hypogeal or epigeal emergence types as to seedling growth or competitiveness. However, seed size did have a direct effect on seedling size, regardless of emergence ' type.

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