Growth and development of lettuce cultivar Brasil- 202, White Boston and Regina inside and outside of a polyethylene greenhouse were compared in Santa Maria, RS. During a winter period of 50 days the greenhouse caused an increase in about 256 degree-days in the temperature values above the base temperature for growth (estimated in 10°C). Mean soil temperature was also 5.3°C higher inside the greenhouse. The growth patterns of plants cultivated inside the greenhouse were similar to those cultivated outside. Growth parameters of leaf surface, shoot fresh weight, dry weight of leaves. stem and roots and the shoot/root ratio were lower outside the greenhouse. The number of leaves per plant was similar in both conditions. Brasil-202 showed earlier growth and higher dry matter accumulation. Protection of plants with polyethylene greenhouses is an efficient technique to improve lettuce crop production in winter.
Lettuce; Lactuca sativa L.; growth; development; protected cultivation
