Fig. 4. Phenotypic analysis of wild-type and acr4 mutant plants. (A,B) Ovule primordia immediately prior to integument initiation in wild-type (A) and mutant (B) plants. (C,D) The initiation of the inner (arrowheads) and outer (arrows) integuments in wild-type and mutant ovules respectively. In the mutant, the irregular initiation of integument outgrowth is visible, with at least two outgrowths observed in one region of outer integument initiation (asterisks), whereas other regions have no outgrowths. (E,F) Ongoing integument outgrowth. In wild-type ovules (E) the leading edges of the integuments are smooth, whereas in mutants (F) they are ragged and often retarded. (The nucellus has snapped off in the right hand ovule of F.) (G) A mature wild-type ovule at anthesis. The outer integument has overgrown the inner integument and nucellus to give a narrow micropyle (m) facing the funiculus (f). (H-J) A weak, a medium and a severe mature mutant ovule phenotype, respectively. In H, the retardation of outer integument (arrow) growth has left an open micropyle within which the inner integument (arrowhead) and nucellus are visible. In I the inner integument (arrowhead) looks relatively normal whereas the outer integument (arrow) has failed to elongate correctly. (J) The inner integument (arrowhead) has failed to grow out leaving the nucellus almost completely exposed. (K) Wild-type sepal margin (arrowhead) showing well organised border cells covered in cuticular decoration. (L) Mutant sepal margin (arrowhead) showing typical irregularities in cell organisation, `lumpy' appearance and regions devoid of cuticular decoration. Scale bars: 20 µm.

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