Day and night temperature effects during grain-filling in oat

Temperature has a large effect on oat (Avena sativa L.) growth and development. The objective of this study was to determine the effects of day temperature (DT), night temperature (NT), and the day-night temperature differential (DIF) during grain filling on oat grain yield and other agronomic traits and to determine if these traits exhibit a thermoperiodic response. Three genotypes of varying maturity (early-, mid-, and late- season) were grown in controlled environment chambers with varying planting dates to synchronize heading date among the cultivars. At heading, plants of each cultivar were divided into nine treatments of all possible DT-NT combinations of 31, 23, and 15°C. The temperature treatments were imposed until the plants were fully mature. Grain yield was 87%, kernel weight 51%, grain-filling period 27%, and grain-filling rate 45% greater at 15°C DT than at 31°C DT with a NT of 15°C. For NT, grain yield was 24%; kernel weight 12%, and grain-filling period 27% greater at 15°C NT than at 31°C NT with a DT of 15°C. NT had no effect on grain-filling rate. DIF had no effect on any of the traits. No evidence was found for a thermoperiodic response for any of the traits; however, optimal conditions for grain yield, kernel weight, and grain-filling period was at the lowest temperature treatment and the possibility of a thermoperiodic response for these traits cannot be dismissed. All cultivars responded similarly to increased temperatures. Under a 16-h photoperiod, the effect of DT was much larger than the effect of NT.