Effect of temperature on growth and phototropism of Arabidopsis thaliana seedlings

Seedlings of Arabidopsis thaliana grown at 25 degrees C responded to a change in growth temperature by changing their elongation rate within the next 150 min. Regardless of whether the new temperature was higher or lower than 25 degrees C, the seedlings grew slower after the transfer at all tested temperatures. When the seedlings were grown for 2 days at 11.5 degrees C, 17.9 degrees C, and 23.5 degrees C and then transferred to the range of temperatures between 4 degrees C and 38 degrees C they exhibited maximum elongation in the temperature range between 18 degrees C and 23 degrees C. The kinetics of first positive phototropism in seedlings transferred from 25 degrees C to 15 degrees C differed from the kinetics exhibited by seedlings transferred from 25 degrees C to 28 degrees C. At 15 degrees C, measurable curvature began 40-50 min after the blue light (BL) pulse and no straightening was evident within 150 min after the BL pulse. Seedlings transferred to 28 degrees C exhibited kinetics of phototropism similar to the phototropic response of plants maintained at 25 degrees C except that straightening began slightly faster in the seedlings at 28 degrees C. Based on these results, it is concluded that changes in temperature conditions affect both the elongation rate of seedlings and a first positive phototropism and that phototropic curvature and subsequent straightening are independently controlled.