Biocondicionamento de sementes de cebola com bioestimulantes a base de algas

Abstract

Onion is the third most economically important vegetable in Brazil, being normally carried out by small and medium farmers. Seed treatment is an important process, as it can promote protection against pathogens and pests and promote plant growth. Priming is a controlled rehydration of the seed, used to obtain gains in germination potential and plant growth. Initially made with water, this technique has demonstrated the possibility of using other compounds. The objective of this research was to verify the effect of the bioconditioning of onion seeds with algae based biostimulants. The work was carried out in the seed and grain laboratories at the Federal University of Fronteira Sul - Campus Chapecó and in the city of Caçador - SC. Onion seeds from the Baia Periforme and Crioula was used, accounting for two separate experiments. The concentrations of the algae solutions were 0; 0.25; 0.5 and 1% of extracts of Ascophyllum nodosum and Solieria spp., used separately. The experiment was divided into two stages: 1) Germination and seedling growth tests in the laboratory; and 2) Evaluation of the emergence of plants and seedling growth in the field. In the laboratory, the experimental design was completely randomized, with a 2x4 factorial scheme (algae x concentrations), separately for each cultivar. The seeds were stored in germination chambers. Initially, the embebition curve of the seeds were determined to adjust the appropriate time of embebition. After that, germination test, length, dry mass, electric conductivity and accelerated aging was analyzed. In field conditions, the experimental design adopted was in randomized blocks, in a 2x4 factorial scheme (algae x concentrations). The production of seedlings in a protected environment was carried out in polypropylene trays, with Meplant© substrate, and the period of analysis was 35 days. The cultivation environment was a screened structure with 50% shading. The variables were percentage of emergence, height, number of leaves, length of roots and dry mass of plants. The data obtained in the two stages were subjected to analysis of variance, comparison of means for the algae factor and regression for the concentrations factor at 5% significance separately for each cultivar. In laboratory evaluation of the cultivar Baia Periforme, the application of extracts caused a linear increase in germination speed. The growth parameters were not altered by the algae extracts. In the evaluation of seedling quality,there was an increase in the percentage of emergence, root length and plant height. However, there was a reduction in levels of shoot dry mass, and root dry mass at high concentrations. Thus, for this cultivar, the use of concentrations between 0,25 and 0,5% is indicated to increase growth and germination. In the laboratory evaluation of the Crioula cultivar, there was a delay in germination, as well as a decrease in root length and dry mass, indicating that for this cultivar, biopriming with algae extracts causes inhibition of germination and growth. In seedlingproduction, there was no statistical difference in all variables, except in the analysis of shoot dry mass, with increases according to the concentrations.