The role of the peanut (Araschis hypogaea) ovular tissue in the photo-morphogenetic response of the embryo

Correlative interactions between the embryo and the ovular tissue in peanut, were studied in vitro. Growth arrest of the embryo in the light was controlled by the ovule. Light perceived by the ovular tissue inhibited embryo growth and the inhibitory effect was diminished by decreasing the amount of ovular tissue remaining attached to the embryo. The suspensor played a major role in the development in vitro of isolated globular and heart-stage but not in the cotyledonary stage embryos. Injury to the suspensor in isolated pro-embryos, inhibited their growth in vitro. Electron microscopy showed disintegrated cells, devoid of starch grains and protein bodies, in nuclear cells surrounding the embryo sac at the micropylar, but not at the chalazal end. This may indicate a role of the suspensor in metabolite absorption by the young embryo. Pro-embryos cultured in a medium with abscisic acid in the dark exhibited a mode of growth arrest similar to that by light. The results suggest that light perceived by the ovular tissue induces the production of substances which diffuse to the embryos and arrest their development.