Tomato fruit setting on high density defoliated tomato plants with similar leaf area index was determined in three environmental conditions, inside polyethylene tunnels. Experiment 1 was carried out in autumn when average solar radiation received by the crop was 8.0 MJ m-2 day-1. Average external temperature was 18.1ºC. Experiments 2 and 3 were conducted in spring, when average external temperature was 19.7ºC. In experiment 2, average solar radiation received by the crop was 12.4 MJ m-2 day-1, whereas in experiment 3 it was reduced to 5.9 MJ m-2 day-1 by a 52% shading net. Plants were grown in bags, spaced 1.0 m between row and 0.3 m within row bags distance, using 5.5 L of a commercial substrate. Nutrients and water were supplied by means of a nutrient solution, delivered daily in order to replace volumes lost by transpiration. Treatments consisted of one (T1), two (T2) and three (T3) plants per bag, leading to plant densities of 3.3, 6.7 and 10 plants m-2, respectively. In T1, three leaves per sympod were kept, with a ratio of 3:1 between number of leaves and inflorescences per sympod. In T2, two and one leaf was kept respectively on two consecutive sympods, alternatively on both plants. The ratio between number of leaves and inflorescences was 3:2. In T3, with three plants per bag, only one leaf per sympod was kept on each plant. The ratio between number of leaves and inflorescences was 3:3. In all experiments, the number of trusses per area in T2 and T3 was two and three times higher than in T1, respectively. The number of fruits per unit ground area was lower in T1 plants and similar in T2 and T3 plants in the first experiment, whereas in the second and third experiments similar values were observed among treatments. Results indicated that tomato plants adjust the number of fruits, and exceeding flowers are aborted. The use of a plant density of 6.7 plants m-2 combined with a 3:2 ratio between number of leaves and inflorescences per unit ground area seems to be the upper limit in maximizing the number of set fruits of this crop.
Lycopersicum esculentum; fruit number; fruit emission; fruit set; competition for assimilates
