Stored metabolites - seed and fruit, Biology

Stored Metabolites - Seed and Fruit

In a large majority of seeds food is stored in the cells of the endosperm. In coconut, wheat and castor bean for example, it is the endosperm which stores the bulk of the food reserves. Food stored in endosperm is utilized by the embryo during development and seed germination. The endosperm is usually a triploid tissue derived from the fusion product of a male gamete (brought by pollen tube) and two polar nuclei in the central cell of the embryo sac. The endosperm surrounds the embryo all around and is ideal for nurturing the embryo till the seedling begins to photosynthesize and becomes antotrophic.

A second seat/site of nutritive tissue in some seeds is the perisperm, which represents the persisting nucellus. Nucellus is observed in some monocot families, such as the Zingiberaceae (to which turmeric and ginger belong), and a few dicotyledonous families, including the Piperaceae (e.g., black pepper) and the Nymphaeaceae (e.g., lotus). In Canna the chalazal cell of the ovule divides repeatedly to form a starch-containing tissue called chalazo sperm. Mature seeds containing persistent endosperm or perisperm are called albuminous and those lacking them exalbuminous.. Mature leguminous seeds lack endosperm. In pea, gram (chick pea) groundnut and a whole range of pulses the large cotyledons of the embryo take up the function of storage of food. In cotton seed also the large, lobed and folded cotyledons are the main repository of nutrients.

Posted Date: 1/23/2013 8:21:02 AM | Location : United States







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