BOTANICAL ASPECTS OF CEREALS ovule. All endosperm cells are ultimately derived An important phase in the life cycle, from the from this first endosperm cell and each inherits point of view of grain quality, is germination chromosomes from three nuclei rather than the This occurs when ripe grain is subjected to more usual two Endosperm cells thus have one and damping to an adequate moisture content at an a half times as many chromosomes as cells else- appropriate temperature. In primitive grains the where in the plant. The details of the develop appropriate conditions are those to be expected ment of endosperm, embryo and other grain in the natural habitat of the species at the issues of different cereals are described in relevant beginning of the growing season, but breeding texts(Kiesselbach, 1980; Bushuk, 1976; Wat and cultivation over many years have diminishe 1987; Hulse et al., 1980; Percival, 1921; Evers this relationship Bechtel, 1988; Palmer, 1989; Hoshikawa, 1967) The processing requirements in respect of Stem extension FIG 2. 14 Stages of plant growth corresponding to the phases defined in Zadoks scale. Major phases are represented by higher order numbers thus: 0. germination, 10 seedling growth, 20. tillering, 30 stem elongation, 40. booting, 50. inflorescence emergence, 60. anthesis, 70. milk development, 80 Within major phases additional lower order numbers indicate events of lesser importance The descriptions corresponding to the numbers on the horizontal axis are: ll, first leaf unfolded ves unfolded; 21, main shoot and I tille 23, main shoot and 3 tillers; 24,ma 4 tillers: 25, main shoot and 5 37, Aag(last)leaf just visible; 39, fag leaf ligule/collar just visible; 41, flag leaf sheath g the term boot refers to the swollen sheath of the last leaf, when the inflorescence within causes it to expand. The inflorescence is said to be in boot