Structural Alterations in Isolated Endosperms of Lactuca sativa L. Achenes.

Endosperm tissue of lettuce (Lactuca sativa L.) achenes germinating in the dark was isolated from the embryo after appropriate time periods of imbibition in the dark and was incubated in water or in gibberellic acid solution in the dark. It was found that endosperms which were dissected from achenes during the first to the eighth hours of imbibition do not show any structural alteration even after 24 h of incubation either in water or in GA(3) while endosperms excised after 9 hours of imbibition show moderate modifications of micropylar area cells if incubated in water for 24 h. Endosperms isolated after 8 hours of imbibition show great structural alterations of their micropylar cells if incubated for the same period in gibberellic acid solution. These results indicate (a) that the presence of the embryo is necessary for a long period for the manifestation of structural modifications of the isolated endosperm; and (b) that the two areas of lettuce endosperm (i.e. micropylar vs lateral) are different.