Growth of lettuce cultivars in a protected environment

Abstract

The objective of this study was to investigate the agronomic characteristics of different lettuce cultivars during growth in a protected environment in the municipality of Videira, in the Midwest region of Santa Catarina. For this purpose, lettuce seedlings, Lactuca sativa L., of different cultivars: Americana [variety (var.) Yasmim], Crespa (var. Lirice), Lisa (var. Stela), Mimosa (var. Natali) and Romana (var. Luisa), were grown in plastic pots containing 5 dm3 of substrate inside the greenhouse of the Instituto Federal Catarinense, Videira Campus. The plants grew with the substrate maintained close to field capacity until the end of the experiment, which lasted 45 days after transplanting (DAT) of the seedlings into the pots. Irrigation control was performed by the gravimetric method (daily weighing of the pots), adding water until the mass of the pot reached the previously determined value, considering the mass of soil and water. The experiment was set up in a completely randomized design (CRD) with four replicates, with five lettuce cultivars (American, Crespa, Lisa, Mimosa and Romana). Each experimental unit consisted of a plastic pot containing one plant. The data were subjected to analysis of variance, and the treatments were compared by the Scott-Knott test (5% probability) using the R^® software program, version 4.3.2. Growth evaluations were performed at the end of the experimental period, at 45 DAT from the seedlings to the pots. At each collection, the following variables were analyzed for each plant (cultivar): height, stem diameter, number of leaves, root and stem length. Leaf, stem, root and total dry matter (leaf, branches and stem, and root) was also evaluated. According to the experimental climatic conditions presented, it is suggested that among the cultivars, Americana and Crespa were the most promising for cultivation, exhibiting growth characteristics that are favorable to the producer, such as shorter stem length, providing greater resistance to early flowering, and increases in leaf dry matter, indicating greater allocation of carbohydrates for leaf growth, a desirable characteristic in the genetic improvement of lettuce plants, being essential in obtaining higher productivity, thus meeting the demands of the consumer market. Among the cultivars, Romana seems to be the least suitable for cultivation, since it can pass prematurely from the vegetative to the reproductive phase, emitting inflorescences, an undesirable characteristic for growth.