Introduction

Seeds contribute on a world basis some 55% of our daily per capita protein and energy supply. Of this, 90% is accounted for by cereals (Duffus & Slaughter, 1980). The contribution is even greater if allowance is made for the inclusion of cereals and other seed crops in the diet of farm animals. It is therefore not surprising that there has long been an interest in the mechanisms regulating seed growth and maturation, since such studies could lead to the identification of key factors involved in the control of yield and quality in the harvested material.

The aim of this chapter is, then, to review present understanding of the control mechanisms involved in seed growth and development. The major emphasis is on the cereals, including barley, wheat, rice, oats and maize. The morphological, physiological and biochemical changes accompanying grain growth and development are described, and the influence of genotype and environmental conditions on these changes is discussed.

Developmental morphology

The cereal seed is surrounded by a seed coat or testa, which is fused to the pericarp, forming a single-seeded fruit known as a caryopsis. The harvested material is termed a grain or kernel; in wheat, rye, triticale, maize, grain sorghum and the naked-grain millets, this consists solely of a caryopsis. In oats, barley, rice and the husked types of sorghum and millet, the grain consists of a caryopsis, together with the lemma and palea, which adhere to the outer surface.