cotyledon - (also called seed leaves) the embryonic leaf within a seed. Dicots (plants like the bean plant above) have two cotyledons. first true leaves - the first two leaves of the plant that emerge from the cotyledon. These leaves are the first to begin the process of photosynthesis. hypocotyl - the part of the stem of a sprouting plant that is above the roots and below the stalk of the cotyledons. primary root - the main, thick part of the root (and the first part to grow). secondary root - small roots that grow from the primary root seed coat - the outer, protective layer that covers the seed. It is shed after the bean sprouts.