epigeal

Epigeal refers to a mode of seed germination in which the seed’s cotyledons emerge above the soil surface as the hypocotyl elongates. The term comes from the Greek epi meaning upon and ge meaning earth. In epigeal germination, the seedling often relies on the elongation of the hypocotyl to lift the cotyledons and shoot system above the ground; the cotyledons frequently become green and photosynthetic, contributing to the plant’s early energy supply.

During this process, the first true leaves usually develop after the cotyledons emerge. The cotyledons may provide energy until photosynthesis begins in the mature leaves. The phenomenon is common in many dicotyledonous plants, particularly several legumes and sunflowers and related species.

Epigeal germination is contrasted with hypogeal germination, in which the cotyledons remain below the soil surface. The two modes reflect different strategies for seedling establishment and energy use, with hypogeal species typically protecting the cotyledons in the soil.