Endogenous Growth Regulators and Summer Tillering of Tall Fescue¹

Abstract

In the southern Corn Belt, tall fescue ( Festuca arundinacea Schreb.) produces most of its vegetative growth during the spring and autumn. Generally little growth or new tiller initiation occurs during midsummer, even though the potential sites (buds) for tiller production are present. Failure of buds to elongate into tillers may be controlled by endogenous growth regulators. We investigated the influence of endogenous plant auxins on the elongation of buds into new tillers for tall fescue grown under field and growth chamber conditions. High temperature in the field and growth chamber (31/17 C) favored the accumulation of endogenous auxin in stem bases, and this appeared related to the inhibition of tiller initiation in early summer. Low temperature in the field and growth chamber (22/11 C) favored the accumulation of auxin in shoots and a high level of shoot auxin appeared related to active tiller development. Endogenous auxin levels in both shoots and stem bases were low in late summer.