Condições de luminosidade e temperatura na germinação de Tagetes erecta L. E Catharanthus roseus (L.) G. Don

Abstract

In Brazil, floriculture has been gaining prominence in recent years and is characterized as one of the most promising business activities in the agribusiness field, especially benefiting from the country's favorable soil and climate conditions and high productivity in small areas. In the southern region, Rio Grande do Sul stands out in the production of ornamental herbaceous plants, important flowers used in landscaping projects. In this sense, understanding the germination process of ornamental species of economic importance is essential to enable a regular supply and aesthetic quality for the consumer market. Thus, the present study aims to trace the germination curve of Tagetes and Vinca seeds as a function of light and temperature. The bioassays were conducted in the seed and plant physiology laboratory of the Federal University of the Southern Frontier, in a completely randomized design, using four replicates of 25 seeds of each species at five constant temperatures of 8ºC, 16ºC, 24ºC, 32ºC and 40ºC with absence and presence of light in a photoperiod of 12 hours of daily light. The evaluation was made through the daily germination count, speed index and seedling length. The results were submitted to the ANOVA test with 5% probability of error using the SISVAR software. In case of significance, regression analysis was performed. The results obtained demonstrate that both Tagetes and Vinca germinate in the dark and in the presence of photoperiod. For Tagetes, darkness enhanced germination at 8ºC and the presence of light induced germination at higher temperatures. For Vinca, better germination results, germination speed index and seedling length were obtained in the dark, between 24 and 32ºC. The species did not germinate at a temperature of 8ºC. Temperatures of 24 and 32ºC increase germination speed and seedling length for both species, but above 24ºC germination is impaired.