Movie S4.

z-stack of the aborting seed shown in Fig. 6I from a +/pur5-2 plant, when embryos in green seeds from the same silique were at the heart stage. The embryo had arrested development at the 2/4-cell stage. The peripheral endosperm has fewer nuclei that are unevenly distributed along the anterior-posterior axis, compared to seeds of comparable developmental stage from wild-type plants. The chalazal cyst failed to develop. The seed was Feulgen stained and imaged under a confocal microscope. Optical sections were acquired at 0.5-nm intervals from the top of the seed coat. The movie was created from a zstack of 96 optical sections. Scale bar is 35 μm.