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Abstract
ABSTRACT Cut sunflower holds significant potential for the floriculture market in Brazil, with its development being strongly influenced by air temperature. This study aimed to determine the thermal sum required for the emergence of various phenological stages and to estimate the phyllochron of 12 newly cut sunflower genotypes in southwestern Mato Grosso, Brazil. The research was conducted in Cáceres, MT, where seedlings were planted in two beds, and ten central plants per genotype in each bed were marked to track reproductive stages, classified as R1, R4, and R5. Air temperature measurements were used to calculate the accumulated thermal sum for the stages emergence-R1, R1-R4, R4-R5, and emergence-R5. A linear regression analysis was performed to assess the relationship between the number of leaves accumulated on the stem and the accumulated thermal sum, enabling phyllochron estimation for each genotype. The accumulated thermal sum for emergence-R1 ranged from 445.29 ºC/day to 791.08 ºC/day, and for emergence-R5, it ranged from 806.51 ºC/day to 1139.10 ºC/day. The relationship between leaf number on the stem and accumulated thermal sum was linear, with a coefficient of determination between 0.98 and 0.99, and phyllochron values ranged from 20 to 26 °C day leaf−1. Thus, the sunflower genotypes assessed exhibited values consistent with standards observed in other genotypes and ornamental species on the market, indicating that they possess commercialization potential and that the region’s climate conditions are suitable for cultivation.
Published Version
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