Figure 6
Development of ovules and aposporic initials, and megasporogenesis pathway in Hypericum perforatum. (a) Ovule showing an asymmetric growth of the integuments giving rise to its characteristic anatropous shape; Bar=30 μm. (b) Ovule primordium (prior to stage 1), bearing a primary sporogenic cell and showing two basal cells undergoing mitosis (indicated by arrows); Bar=20 μm. (c, d) Ovules at stage 1 bearing a megaspore mother cell; Bar=20 μm; (e–g) Ovules at stage 2 showing a megaspore mother cell or a linear tetrad of megaspores together with one or more aposporic initials in the deeper part of the chalaza; Bar=30 μm (nu, nucellus; fu, funiculus; PSC, primary sporogenic cell; MMC, megaspore mother cell; T, tetrad; fM, functional megaspore; Ai, aposporic initial; ii, inner integuments; oi, outer integuments).
