The Relation of the Cotyledons to Root Development of Pine Embryos Grown in Vitro.

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Abstract
Excised mature embryos of Pinus lambertiana were grown under aseptic conditions using a modified Knop''s solution in 1% agar with and without 2% sucrose. Sucrose supplied to the embryos through the cotyledons exerted a much greater beneficial effect on rate and duration of root growth than when supplied directly to the root. The effect of varying concentrations of IAA, GA, and TIBA on root growth and embryo development was also studied. The inhibitory effect of IAA on root growth was apparent at all concentrations; however root morphology appeared somewhat modified in the presence of sucrose. There was an initial stimulation of root growth by the addition of GA, but the effect was not sustained; the shoots did not exhibit a beneficial response. Embryo growth was retarded by TIBA and the polar auxin-transport system was shown to be effectively disrupted.