Influence of Cool and Warm Temperatures and Temperature Reversal at Inflorescence Emergence on Growth of Timothy, Orchardgrass, and Tall Fescue1

Abstract

AbstractTimothy (Phleum pratense L.), orchardgrass (Dactylis glomerata L.), and tall fescue (Festuca arundinacea Schreb.) were grown from small propogules in pots of soil in growth chambers to evaluate the effect of temperature and temperature change on flowering, tillering, dry matter accumulation and distribution, and leaf‐blade area accumulation within and among species.Temperature greatly influenced maturation rate, growth rate, yield, tillering, leaf‐blade area, specific leaf‐blade weight (SLW), and dry matter (DM) distribution within each species. Except for maturation rate and DM distribution, each parameter was highest for all three species in cool (C, 18 C day/10 C night) or warm‐cool (WC, 32 day/24 C night with a change to 18 C day/10 C night at early inflorescence emergence) temperature regimes. Flowering in timothy was not affected by temperature. Significantly fewer flowering culms were obtained in orchardgrass at warm (W, 32 C day/24 C night) compared with C temperatures, while the opposite was true in tall fescue. Late anthesis in each of the grasses occurred first in the W regime and last in the C regime. Maturation rate, after switching from cool to warm (CW, 18 C day/ 10 C night with a change to 32 C day/24 C night at early inflorescence emergence) or warm to cool temperatures (WC) at early inflorescence emergence, varied among the three species. Timothy had the largest increase in maturation rate following the change from C to W temperatures, while that of tall fescue was least affected by the temperature change. Influence of temperature regimes on DM distribution among plant parts varied among species. Timothy was most sensitive to changes from C to W temperatures, while tall fescue was least sensitive. Warm temperatures slowed leaf‐blade area accumulation in orchardgrass and tall fescue in the CW regime and completely stopped it in timothy. Cool temperatures in the WC regimes stimulated leaf‐blade area accumulation in all three grasses. SLW of all three grasses increased with growth stage. Tall fescue had the highest SLW averaged over temperatures and growth stages, followed by orchardgrass and timothy. Change in temperature in the CW regime was followed by a decrease in SLW in each species compared with the C regime, while the opposite was true in the WC compared with the W regime. Timothy, followed in order by tall fescue and orchardgrass, produced the most DM in the C, CW, and WC regimes. Orchardgrass and tall fescue had similar DM yields which were higher than timothy in the W regime. Dry matter accumulation (DMA) rates in corresponding temperatures regimes were similar among species.It was concluded that the grasses differed in growth and development response to temperature and in sensitivity to temperature change. Differences in total plant yield among the three grasses in comparative temperature regimes were due to differences in DMA rates and in length of growth period.