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Influence of Gibberellic Acid on the Winter Growth of Varieties of Tall Fescue (Festuca arundinacea Schreb.)¹

The winter growth of varieties of tall rescue (Festuca arundinacea Schreb.) that had originated from the Mediterranean region (‘Oregon 1000’ and ‘Tunisian’)and northern Europe (‘Alta’) were studied outdoors in the Mediterranean climate of western Oregon, and in controlled environment chambers.

Cubes of sod taken during the winter months from swards of Alta and Tunisian showed that Alta had a greater density of tillers and buds, and based on etiolated regrowth, a higher level of reserves. Monthly sowing of seed in pots from May through October showed that a preceding exposure to summer conditions was unnecessary to establish differences in winter growth.

During the winter, foliar growth of both Alta and Oregon 1000 was increased by a temperature of 15 to 20 C, a foliar spray of 0.1% gibberellie acid (GA), and possibly by a long photoperiod. Although chlorophyll concentration in the foliage was reduced by GA, the total chlorophyll per plant was increased by 10 to 30%.

Regrowth from reserves at 7/3.5 C (day/night) was described by a monomolecular function. The time taken for 63% of the total regrowth to be attained was 103 and 53 days for Alta and Tunisian respectively; these response times were halved for both varieties by GA.

Tunisian made more growth than Alta at 7/3.5 C, 19 langley per day (400 to 700 nm). The water soluble carbohydrates (WSC) were 6.4 and 7.9% of the total dry weight of Alta and Tunisian respectively, with greater concentrations in stems than leaves and roots; fructosans were the dominant WSC with sucrose, followed by reducing sugars of lesser concentrations. The level of WSC was increased by GA to 12.0 and 11.0% for Alta and Tunisian respectively. The greatest increase was that of sucrose.

Key Words: Ecotype • Growth analysis • Regrowth • Photosynthesis • Carbohydrates

² Former Research Assistant and Professor, respectively, Department of Farm Crops, Oregon State University, Corvallis, Oregon. Senior author now at the Department of Soil Science, University of Guelph, Guelph, Ontario, Canada.

Received for publication March 30, 1970.