Qualidade fisiológica de sementes de alface em diferentes temperaturas

Abstract

Lettuce is a crop of the leafy vegetable group, with a great emphasis on Brazilian food and an expressive percentage of production for the farmers working in its cultivation. The propagation of lettuce is made by seeds, which have as obstacles, the reduced size and cultivation dependent on the temperature, humidity and luminosity, which can lead to common dormancy processes in the crop. The objective of this work was to evaluate the effect of different temperatures on the physiological quality of lettuce cultivars. The experimental design was completely randomized in a factorial scheme (5x8), with four replications, where each of the replicates was composed of 50 seeds, totaling 200 seeds per treatment. The treatments were composed of five temperatures: 15; 20; 25; 30 and 35ºC and eight cultivars: White of Boston, Great Rapids, Great Lakes, Hanson Repolhuda, Four Seasons, Regina, Salad Bowl and Veneranda. The seeds were germinated on Germitest® paper moistened with distilled water and kept in BOD for seven days. Seed quality was evaluated through the mass of one thousand seeds, first count test, germination standard test, germination speed index and substrate emergence. To analyze the vigor of the seeds, they were submitted to the accelerated aging test at 41ºC for 48 hours and to the tetrazolium test. Seeds were also evaluated for substrate emergence for 4, 7 and 15 days. It was concluded that the majority of cultivars analyzed had temperatures at or above 25ºC reduction in speed and percentage of seed germination. It was also observed that in the temperature of 35ºC all the cultivars analyzed did not present germination. The cultivars Grand Rapids and Four Seasons differed in relation to the others for most of the analyzed characteristics, being that these cultivars presented greater potential of germination than the others in the temperature of 30ºC, besides presenting values in relation to its vigor by the tetrazolium test . These alternative cultivars may be used to grow lettuce in the hottest periods of the year in the Campos Gerais region.