Studies on the ontogeny of the pigment strand in the caryopsis of wheat

Abstract

The grain of wheat has a groove that extends inward nearly to the centre of the grain. At the base of this crease and extending through its length there is a strand of coloured tissue, the pigment strand. At about 3 days after anthesis the cells of this strand of tissue are similar to meristematic cells, possessing thin walls and the usual complement of organelles. At about 9 days after anthesis the cell walls thicken and lignify. The vacuoles of the lignified cells then begin to accumulate numerous refractile and birefringent granules which stain strongly with the sudan dyes. At about the same time an electron dense layer of adcrusting substance begins to form and accumulate, initially near that part of the wall which is not traversed by the plasmodesmata. Later, it spreads out towards the cell lumen and plasmodesmata and becomes electron-lucent. The staining reactions of the adcrusting substance suggest that it is suberized, but its origin is not clear. At the final stages of development, the cell contents of the pigment strand become disorganized and crushed. The functional significance of the pigment strand in relation to grain development and maturation is discussed. © 1970 CSIRO.