Estimativa do filocrono em girassol de corte na região norte do Rio Grande do Sul

Abstract

The production of cut flowers can be an income diversification alternative for small producers, such as the cut sunflower. The experiment aimed to estimate the phyllochron of sunflower (Helianthus annus L.) of the cultivar Vincent Choice in the field, in three municipalities in the northern region of Rio Grande do Sul. The experiment was conducted in three municipalities in the northern region of Rio Grande do Sul, namely Caiçara, Novo Xingu and Seberi. The number of leaves (NF) of the marked plants was collected weekly until the Final Number of Leaves (NFF). The daily thermal sum (STd) was calculated as base temperature for the sunflower Tb = 7.2ºC. The daily thermal sum was accumulated from emergence, resulting in the accumulated thermal sum (STa). A simple linear regression was performed between the number of leaves (NF) and the accumulated thermal sum (STa) to calculate the phyllochron. An R2 ranging from 0.98 to 0.99 was obtained for all municipalities and sowing dates. The average values ​​of Phylochron obtained by municipality was 28.33 ºC day leaf-1, being the average of Novo Xingu of four sowing dates, the average of Seberi of 27.58 ºC day leaf-1 in two sowing dates and two sites, and the only Caiçara sowing date of 21.69 ºC day leaf-1, with a production cycle of around 60 days. It is possible to verify the influence of air temperature on the phyllochron results in the cities studied.