Effect of Varying Temperature Regime on Phyllochron in Four Warm-Season Pasture Grasses

Abstract

Using accumulated temperature measures to predict plant development may provide guidance on timing of management practices to minimize competition between warm and cool-season components of mixed pastures. However, temperature and plant development relationships for warm-season pasture grasses common in the southern Great Plains of the USA have not been extensively studied. Under controlled environment conditions, base temperature (T base ) values were determined for Big bluestem ( Andropogon gerardii Vitman), Indiangrass ( Sorghastrum nutans , (L.) Nash), Little bluestem ( Schizachyrium scoparium (Michx) Nash) and, Sideoats grama ( Bouteloua curtipendula (Michx) Torr). Measures of the accumulated temperature requirement for the phyllochron (leaf appearance interval) were made under a range of temperature regimes for these same species. Mean T base was 8.1 &deg C and differences among species were not significant (P > 0.05). Within temperature regimes mainstem leaf appearance was closely and linearly related to accumulated temperature above T base . Increase of 7.5 &deg C in night temperature increased phyllochron by a mean of 43%, but similar increase in day temperature only increased phyllochron by 16%. Phyllochron increased by 6.4 &deg C leaf -1 for each 1 &deg C increase in daily mean temperature within the range of 15.0 &deg C to 22.5 &deg C. If accumulated temperature measures are to monitor reliably the development of warm-season grasses, allowance must be made for changes in phyllochron as the growing season progresses.