Abstract
Most vascular plants contain Δ5-sterols as the predominant type; however, a few species such as Medicago sativa, have mainly Δ7-sterols. The Δ7-sterols of alfalfa are isomers of the common Δ5-sterols and are generally assumed to be their immediate precursors. Light had a significant influence on the sterol status of M. sativa. High light intensity and a long day favored the accumulation of dihydrospinasterol; a short day and low light intensity, particularly darkness, favored spinasterol accumulation. These data for Δ7-sterol plants agree with those reported for Δ5-sterol plants; light favors the accumulation of the monounsaturated 29 carbon sterols and darkness favors the accumulation of the diunsaturated sterols. Proposed is a mechanism to explain the effect of light on the accumulation of Δ7- and Δ5-sterols.
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Selected References
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