Structural changes in the ovary of Pisum sativum L. induced by pollination and gibberellic acid

Early changes in the morphological organization of the ovary wall of Pisum sativum L. cv. Alaska during the transformation of the ovary into young developing fruit were studied. Changes in either pollinated or unpollinated and gibberellic acid (GA₃)-treated ovaries were very similar and were characterized by a rapid enlargement of mesocarpic cells and an increase in the number of cell ‘layers’ in the endocarp. Unpollinated and untreated ovaries in emasculated flowers continued growing slowly until 2 days after anthesis and then began to degenerate. Degeneration was initiated in the endocarp, and on day 4 after anthesis the endocarp cells were completely wrinkled and no cellular ‘layers’ were distinguishable. The beginning of endocarp degeneration was coincident with the loss of sensitivity of unpollinated ovaries in response to GA₃.