Growth and development temperature influences level of tolerance to high light stress.

The influence of growth and development temperature on the relative tolerance of photosynthetic tissue to high light stress at chilling temperatures was investigated. Two tuber-bearing potato species, Solanum tuberosum L. cv Red Pontiac and Solanum commersonii were grown for 4 weeks, at either 12 or 24 degrees C with 12 hours of about 375 micromoles per second per square meter of photosynthetically active radiation. Paired leaf discs were cut from directly across the midvein of leaflets of comparable developmental stage and light environment from each species at each growth temperature treatment. One disc of each pair was exposed to 1 degrees C and about 1000 micromoles per second per square meter photosynthetically active radiation for 4 hours, and the other disc was held at 1 degrees C in total darkness for the same duration. Photosynthetic tissue of S. tuberosum, developed at 12 degrees C, was much more tolerant to high light and low temperature stress than tissue developed under 24 degrees C conditions. Following the high light treatment, 24 degrees C-grown S. tuberosum tissue demonstrated light-limited and light-saturated rates that were approximately 50% of their paired dark controls. In contrast, the 12 degrees C-grown tissue from S. tuberosum that was subjected to the light stress showed only a 18 and 6% reduction in light-limited and light-saturated rates of photosynthetic oxygen evolution, respectively. Tissue from 24 degrees C-grown S. commersonii was much less sensitive to the light stress than was tissue from S. tuberosum grown under the same conditions. The results presented here demonstrate that: (a) acclimation of S. tuberosum to lower temperature growth conditions with a constant light environment, results in the increased capacity of photosynthetic tissue to tolerate high light stress at chilling temperature and (b) following growth and development at relatively high temperatures S. commersonii, a frost- and heat-tolerant wild species, has a much greater tolerance to the high light stress at chilling temperature than does S. tuberosum cv Red Pontiac, a frost-sensitive cultivated species.