Diferentes comprimentos de onda e intensidades luminosas na germinação de sementes de Melocactus zehntneri (chapéu-de-frade) e desenvolvimento vegetativo de Hylocereus undatus (pitaia).
Magnani, Mariana Freitas Campos
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Melocactus zehntneri and Hylocereus undatus are cacti popularly known as Chapéu-de-Frade and Pitaia, respectively. They are cacti with great commercial potential and have great importance in the economic movement of the country. As a way to establish improvements in the production of these species, the present project aimed to determine the influence of wavelengths and light intensity on the germination of M. zehntneri seeds and on the in vitro vegetative development of H. undatus. To this end, the seeds of fenugreek hat were disinfected and sown in Petri dishes containing two layers of filter paper saturated with 5 mL of sterile deionized water. Later they were placed on different light intensities and wavelengths provided by Light Emitting Diode (LED) lamps and grown in a growth room, these in the wavelength ranges of blue, red, red + blue (3:1) and, as a control, white light. As a complementary experiment to the germination, the influence of the light deprived environment on the germination of M. zehntneri seeds was tested, being taken to the bright environment of the growth room after three periods: 10, 20 and 30 days. Pitaia was subcultured in vitro from the initial material and placed in flasks containing culture medium. Subsequently, they were randomly arranged on three different light sources: blue, red, blue + red and, as a control, white light. The effect of lights on the germination of M. zehntneri seeds influenced the development of different pigments in the seedlings. The wavelengths that had the best effect on germination were the red and white spectrum under intensity III and red + blue under intensity II, reaching 67.5%, 72.5% and 70% of germinated seeds, respectively. In the in vitro development of H. undatus, the photoresponse under the blue, red + blue and white wavelengths were the most vigorous, presenting the highest mean values for the variables analyzed. In the light deprivation experiment for three periods of time, all treatments caused the germination rate to be reduced to almost zero, even after being exposed to light, suggesting that the seeds were induced to secondary dormancy.
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