Metabolismo bioquímico, produção e avaliação póscolheita em plantas de alface submetidas à aplicação de silicato de cálcio foliar

Abstract

Lettuce is considered the most consumed leafy vegetable in Brazil, however, some obstacles need to be overcome in this production chain, such as its short shelf life, due to its high water content in its composition, favoring its deterioration and poor quality. However, studies have shown positive results in the use of silicate fertilizer in various agricultural crops, because, when accumulated in the cuticle of the leaves, it promotes a reduction in mass loss. In the same way, Si can also act on the metabolism of carbon and nitrogen. Therefore, the objective of the study was to determine the effects of doses and two sources of silicon, via leaf, on growth, production, post-harvest conservation and biochemical metabolism in curly lettuce plants in a greenhouse in two application times. Four experiments were carried out, and in Experiment I, a 2x5 factorial scheme was followed, with the sources of calcium silicate and sodium metasilicate and five doses of silicon: 0, 2, 4, 6, 8 mg L-1 Si, with six repetitions, lettuce plants being grown in pots filled with substrate. In experiment II, three lettuce plants were removed and taken to the refrigerator, weighing at intervals of five and 10 days for post-harvest evaluation and the same conditions as in experiment I were submitted. Experiment III was in randomized blocks, factorial 5x2, with four repetitions, totaling 10 treatments, (5 doses of Si: 0; 2; 4; 6 and 8 mg L-1 and two application times: 20 and 27 DAT). The IV experiment was in subdivided plots, with 5 doses of Si (0; 2; 4; 6 and 8 mg L-1), two times of foliar application (20 and 27 DAT), with four weighing intervals (5, 10, 15 and 20 days after harvest) and three replications. Lettuces were grown in Leonard pots, filled with sand, receiving nutrient solution. It is concluded that in experiment I and II in the tested concentrations there is a beneficial effect of silicon in the form of calcium silicate, with increments in the number of leaves, fresh and dry mass of the stem, fresh and dry mass of the leaves, fresh and dry mass of the aerial part, fresh and dry root mass, reduction in root length and weight loss during the post-harvest conservation period and the use of sodium metasilicate via foliar application on lettuce plants is not recommended. In experiments III and IV, the foliar application of Si influenced the growth variables: an increase of 18% in the dose 4 mg L-1 for plant height, reduction in length and fresh root mass, and in the biochemical variables there was a reduction in ammonium content and variations in nitrate content. The greatest loss of mass occurred at 27 DAT at a dose of 2 mg L-1 compared to 20 DAT.