PHYSIOLOGY OF FLOWER DEVELOPMENT IN TROPAEOLUM MAJUS L.

Know as Garden Nasturtium, Indian Cress or Monks Cress, this perennial flowering plant is native from the Andes of South America. It is used as non-conventional fresh vegetable, as well as a medicinal herb and as ornamental plant in landscape projects. Its flower has flavor similar to watercress, being used as an exotic ingredient in green salads. Despite of the colorfulness of the flowers and fast growth of the plant, the use as ornamental flower is still limited. In addition, there is only scarce information available on the physiological changes throughout the flower opening and senescence. Thus, in this work were determined: the production of ethylene and CO₂, content of carbohydrates and anthocyanin pigment in five stages of flower development, as follow: 1 – closed bud flower, showing some petal color at the tip of the bud end; 2 – closed bud flower, showing the color of the petal in whole surface; 3 – recent fresh unfold petals; 4 – complete opened flower without symptoms of senescence; 5 – senescent and signs of wilted petals. Production of CO₂ decreased with the flower opening and senescence, and compared to the first stage of development, a reduction of 72% was detected at stage five. There was an increase of 62% on ethylene production from the first to the second and third stage of development, followed by a sharp decline in the last two stages. Regardless the stage of flower development, starch was the minor non structural carbohydrate, showing a continuous decrease with the flower ageing. Total soluble sugar increased by 66% from the stage 1 to 2, keeping stable up to the stage 4, and then fell by 54% when the petal were completely wilted. Petals anthocyanin content had a slight reduction from the stage 1 to 3, followed by elevation up to the end of flower senescence.