integumenten

Integumenten, in botany typically referred to as integuments in English, are the protective coverings surrounding the ovule of seed plants. The term denotes one or two layers of sporophytic tissue that envelope the nucellus during ovule development. In gymnosperms there is usually a single integument, whereas most angiosperms possess two: an outer integument and an inner integument.

The integuments originate from the ovule primordium and grow to enclose the nucellus, leaving a small opening called the micropyle at the chalazal or micropylar end. The micropyle serves as the entry point for the pollen tube during fertilization. As the ovule matures and fertilization occurs, the integuments typically develop into the seed coat, or testa, providing protection and, in many species, contributing to the seed’s texture and coloration.

Variation among taxa is common. The number, thickness, and degree of fusion of the integuments can differ, influencing seed coat morphology and permeability. In some lineages, one integument may be reduced or lost, while in others the integuments contribute additional tissues or pigments.

Beyond plants, the term integument is used in other biological contexts to refer to coverings or skins, but in the botanical sense, integuments specifically describe the ovule’s protective layers that culminate in the seed coat. See also ovule, nucellus, micropyle, and testa.