plants, especially monocots, parts of the nucellus enlarge or proliferate after
fertilization, and have a role as a regulating or storage tissue for the
developing embryo. Seed storage tissues derived from the nucellus are termed
perisperm. In some monocots (e.g. some members of the order Poales) endosperm
is entirely absent from the mature seed, and perisperm represents the primary
storage tissue. Seeds of Yucca possess perisperm that contains membrane-bound
protein and oil bodies within the cells, together with reserve carbohydrates in
the thick cell walls. Some members of the monocot order Zingiberales (gingers,
bananas and their relatives) possess perisperm, but this is often entirely
compressed in the mature seed, with only the cell walls remaining (e.g. Musa).
In other members of Zingiberales (e.g. Canna), mitotic activity during ovule
development causes the chalaza region of the nucellus to become massive; this
region is then sometimes termed a pachychalaza. In Acorus the perisperm is
dermal in origin, formed from nucellar epidermal cells that elongate and become
filled with transparent proteinaceous cell contents.