The experiment was conducted at the Universidade Federal de Mato Grosso experimental area, in Cáceres, Mato Grosso State, from May to August 2011, with the objective of evaluating the influence of different environments and spacings in the production and tolerance to early bolting of romaine lettuce cultivar Sophia. The experimental design used was a randomized block design in a 2 x 5 factorial design, with two spacings (30 x 30 cm and 25 x 25 cm) and five protected environments (with 30 and 50% shade screens, 30 and 50% thermo-reflective screens and an open field), totaling ten treatments with four replicates each. The plots consisted of four rows with five plants each, totaling twenty plants per plot. The six central plants were considered as useful area for yield evaluation. The plots that used the spacing 30 x 30 cm had 1.8 m² each, and the 25 x 25 cm plots had 1.5 m² each. Seedlings were transplanted at 26 days and the crop was harvested 46 days after transplanting. The 25 x 25 cm spacing between plants and the open field provided the highest yield of romaine lettuce. However, the time for early bolting of plants in open field was shorter than in environments with shading screens or thermo-reflective screens.
flowering; greenhouse crops; Lactuca sativa spacing; light incidence
