EFFECTS OF SHADING OF THE LEAF SHEATH ON THE GROWTH AND DEVELOPMENT OF THE TILLER STEMS OF KENTUCKY BLUEGRASS

Abstract

Two separate greenhouse experiments were conducted to measure the effects of shading of the leaf sheath on the growth and development of tiller stems of cultivars of Kentucky bluegrass (Poa pratensis L.). In the first experiment, four cultivars were grown as single plants and the initial stem was shielded, allowing the tip of the leaf blade to protrude slightly but retaining the sheath in darkness. As growth of the tiller proceeded, further shields were added in a similar fashion for a growth period of 234 days. The second experiment was similarly conducted but included nine cultivars representing a wide range of latitudinal origin. They were grown for a period of 188 days. All shielded stems were much longer than the unshaded stems and developed into long aerial rhizomes with vegetative rhizome-type buds with cataphylls, indicating the morphogenic effect of light on the leaf sheath and the apparent insensitivity of the leaf blade in this reaction. The growth of the stem and buds of the cultivars Windsor, Merion, Geary, and Belturf was less than the growth of stem and buds of Fylking, Pennstar, and Nugget, whereas growth of the uppermost leaf blade was greater. Fylking, Pennstar, and Nugget produced longer stems with many actively growing side shoots and a shorter upper leaf blade. This method of shading might be used as a screening technique in a selection program, particularly for Kentucky bluegrass.