Effects of temperature and radiation on lettuce growing.

Lettuces were planted in the spring at 20 X 25 cm in glasshouses with several temperature regimes and differing light transmission (43-76%), and the effects were determined of air temperature and radiation on the percentage soil cover and yield. With heated, lightly heated and unheated glasshouses the time from planting to almost 100% soil cover was 33, 47 and 54 days, respectively, equivalent to about 600 degree-days. Variations in the total radiation received during these periods were marked. Growth in terms of fresh weight increase was slow initially under all conditions, but when the plants had attained about 60 g fresh weight they grew rapidly, and subsequent fresh weight increases were closely correlated with total radiation. (Abstract retrieved from CAB Abstracts by CABI’s permission