On the Structure of Lettuce (Lactuca sativa L.) Endosperm during Germination

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Abstract
Endosperm cells of lettuce (Lactuca sativa L.) are characterized by thick cell walls and dense cytoplasm which contains numerous protein bodies. Other organelles such as nucleus, mitochondria, plastids and dictyosomes are typical of plant cells. Light and electron microscopy reveal that before radicle emergence micropylar cells of endosperm tissue undergo drastic protoplast alterations. These alterations seem to be the only structural modifications before rupturing of the tissue since the walls of the endosperm cells seem to degrade only after radicle emergence. The differential behaviour of the micropylar area of the endosperm before radicle emergence and the observation that the micropylar cells remain metabolically active long after radicle emergence while the rest of the tissue is almost completely disintegrated, suggests that the endosperm cells of the micropylar area may have a role other than being a main reserve site like the rest of the endosperm.