Temperatura base, filocrono e métodos para avaliação do potencial fisiológico em sementes de quinoa

Abstract

Quinoa belonging to the Amaranthaceae family is an annual plant widely cultivated in the Andean region, where climatic conditions are severe due to water scarcity and temperature variations. Despite the agronomic and food potential, little is known about the thermal needs of the crop and there are no official recommendations for conducting vigor tests. The objective of this work was to determine the lower base temperature (Tb) and phyllochron and to establish a methodology capable of evaluating the physiological quality of quinoa seeds through the tests of accelerated aging (EA) and electrical conductivity (CE). In the period from 2016 to 2018, three experiments were conducted, one in the field and two in the laboratory, which are presented in the form of three chapters. The experiments were carried out in the experimental area of the Department of Phytotechnics and in the Didactic and Seed Research Laboratory. To determine Tb and phyllochron and the accumulated thermal sum was calculated from the germination up to the fifth pair of leaves in eight sowing dates. The seed experiment was conducted with four batches from the field experiment, which were characterized by tests of first germination count; germination; emergence of seedlings in substrate; aerial and root length, thousand seed mass and initial water content. The accelerated aging test was carried out with two temperatures (41 and 45º C) for periods 12, 24, 36, 48, 60 and 72 h. The electrical conductivity with 25, 50 and 75 seeds at 20 ° C, in two volumes of deionized water: 25 and 50 mL. The readings were taken in five periods of imbibition: 1, 2, 3, 4, 5 h. The results showed that Tb was 7 ° C and the genotype Q 13-31, required 28 °C leaf day-¹. The accelerated aging test conducted at 45 ºC, for 12 hours, and the electrical conductivity test with 50 seeds soaked in 50 mL of deionized water, for 2 h are efficient to detect differences in vigor between the quinoa seed lots.