Anatomy of stone and seeds

Introduction
Most of us have a good idea what fruits and vegetables are when we eat them, it is difficult to provide a definition for the convention of just what makes one food a vegetable and another a fruit. For a botanist, the definitions are easier; a fruit is the structure of an angiosperm that develops from the ovary and accessory tissues and surrounds and protects the seed(s).

The process of fertilization initiates both seed and fruit development. While seeds are developing from the ovules, the ovary tissue undergoes a series of complex changes that results in the development of the fruit. Many fruits are “fleshy” and contain sugars that attract animals who disperse the enclosed seeds to new locations after successfully passing through the digestive system of the animal. Non-fleshy, fruits use other mechanisms for seed dispersal. In some plants, fruits can develop without fertilization. This is called parthenocarpy, and such fruits are typically seedless.

Fruits occur only in angiosperms. As the embryo and endosperm develop following double fertilization, the ovary increases in size and is gradually transformed into a fruit. During this process, the ovary wall grows and differentiates, resulting in the fruit wall, or pericarp. The ovule enlarges into a seed, and tissues of the inner (if present) and outer integuments become the seed coat. With the exception of parthenocarpy fruits are developed only after double fertilization. As the embryo develops, parenchymatous extra-embryonic tissues of a flower undergo complex taxon-specific histologic modifications designed for embryo protection and seed dispersal. The other floral parts, i.e. style, perianth and androecium, usually dry up and fall off. At the same time both the cells of the pericarp and those of the seed coat divide and grow. The cells often contain chloroplasts capable of intense photosynthesis, which may provide significant amounts of assimilates for the growing heterotrophic embryo. ( Marshall, and Grace,1992).

The morphology and internal structure of fruits are very diverse. These differences are taxon-specific and they are, to a considerable extent, related to dispersal and germination strategies. The classification of the fruits may be based on the consistence of the pericarp as to whether it is dry and hard, or soft and fleshy. Fruits may also be classified on the basis whether they dehisce or not when ripe and whether they are single-seeded or multiple-seeded. In single-seeded indehiscent fruits, the unit of dissemination is fruit itself rather than seed.