Figure 7.

Maternal cells in stressed ovules (ov) underwent extensive DNA nicking or fragmentation. In B, D, and F to H, nicked DNA was fluorescein labeled (yellow), while cell walls autofluoresced (red). In A, C, and E, DAPI-stained nuclei were observed (blue). A and B, In healthy pistils, DNA was intact or unbroken. C and D, In stressed pistils, the DNA in many integument nuclei and the chalaza nuclei was nicked. By contrast, nuclei in the carpel walls (cw), stigma (st), and style were not modified in this manner. E and F, While maternal cells from stressed ovules exhibited DNA fragmentation, the nuclei in the gametophyte (arrows) were undamaged. G and H, Embryo and endosperm nuclei from stressed plants did not exhibit any DNA fragmentation or nicking. tt, Transmitting tract.