Development of the ovular structures in peach [Prunus persica (L.) Batsch]

Abstract

Changes in the ovular tissues of peach (Prunus persica (L.) Batsch) were studied from anthesis to fertilization or degeneration in pollinated and unpollinated flowers. During this time the ovule undergoes a continuous developmental process. At anthesis the megagametophyte is immature and is not fully developed until 12 days later. During the first three weeks following anthesis the ovule increases in length from 400 to 1200μUm, and the nucellus and integuments undergo various changes particularly in the distribution of starch and cutin. These appear to be connected with early embryo sac nutrition and protection. As the ovule matures, starch accumulates mainly in the embryo sac, integuments and at the nucellar tip. This starch disappears during early embryo sac elongation. Concomitant with starch depletion, the cutin that separated the integuments from the nucellus vanishes. Other cutin accumulates between cells in the nucellar tip, thus protecting and isolating the embryo sac. Most of these changes appear to be a fixed feature of ovule development since they were also observed in a few long lived ovules in unpollinated flowers. However, in unpollinated flowers development of most of the ovules is soon interrupted: callose accumulates af the chalaza, starch disappears and the ovules degenerate.