EMERGENCE OF SEMIDWARF AND STANDARD WHEATS, AND ITS ASSOCIATION WITH COLEOPTILE LENGTH

The relationship between coleoptile length, depth of sowing and emergence of wheat was examined by measuring the emergence of 10 semidwarf and standard varieties from 4 sowing depths under different soil conditions in 2 yr. The coleoptile lengths of the same varieties were measured under dark, controlled-environment conditions. The emergence from deep sowings depended on the coleoptile length of the variety. When the depth of sowing exceeded the coleoptile length of each variety, its emergence was drastically reduced. The semidwarf wheats had shorter coleoptiles than the standard varieties, so the depth at which their emergance was drastically reduced was shallower than for the standard varieties. Since semidwarf varieties developed for the Victorian [Australian] wheat growing areas would be 70-90 cm high, they would have emergence comparable to ''Olympic'' unless sown deeper than 11-14 cm under normal soil conditions, or deeper than 10-11 cm under hard compacted or crusted conditions. The importance of sowing all varieties, but particularly semidwarf varieties, at the recommended depths is emphasized. A very close association was found between mature plant height and coleoptile length within the semidwarf wheats studied (r = 0.90).