Avaliação da germinação e vigor de sementes de Plathymenia reticulata Benth

Abstract

Brazil is a country of extreme diversity in relation to forest formations, and a great part of these species, even today, has not been properly studied or there are relatively few studies available of them, such is the case of the Plathymenia reticulata Benth. P. reticulata, also known as “candeia” or “vinhático”, is a pioneer species from South America, occurring in Brazil in the Cerrado and Atlantic Forest biomes, classified as of high economic interest due to its great use potential in the most diverse sectors and areas, such as medicinal use, for sawmills or handicrafts. The present study aimed to contribute to the analysis of forest seeds by use of biometric characteristics of the seeds, establishing the methodology and appropriate environmental conditions to evaluate the germination and vigor of the seeds, as well as the initial growth of P. reticulata seedlings. For the biometric evaluation of the seeds, it was carried out a manual measurement of the length, width and thickness of 100 seeds taken at random. The pre-germination treatments tested were imbibition of the intact seeds in distilled water at room temperature for 24 h; mechanical scarification with sandpaper for mass n. 100 on the opposite side of the hilum, until the first sign of appearance of the cotyledons; mechanical scarification with the same type of sandpaper but followed by imbibition of the scarified seeds in distilled water, at room temperature, for 24 h; and imbibition in water at 80°C until it achieved room temperature, in addition to the control, where the seeds have not undergone any type of treatment. The effects of the substrates blotting paper, paper towel, sand, coconut powder, medium and fine vermiculite, of the different constant temperatures (15, 20, 25, 30, 35, 40°C) and of the alternating one (20- 30 °C) were evaluated on the germination and vigor of the seeds and seedlings of the species studied species. Different sowing depths (0.0, 0.5, 1.0, 1.5 and 2.0 cm) were tested to verify their influence on the emergence of P. reticulata seedlings. With the results obtained, it was possible to conclude that P. reticulata seeds have a medium diversity in their biometric characteristics, being the thickness and the length of seeds the characteristics with greater and smaller variability, respectively; the best pre-germination treatment for overcoming dormancy is the mechanical scarification with sandpaper for mass n. 100 on the opposite side of the hilum, until the appearance of the cotyledons, with or without further imbibition in distilled water for 24 h; the temperatures that provided greater germination and vigor of seeds and seedlings were 20 and 25°C, when the substrates used are blotting paper, paper towels, medium and fine vermiculite. However, the temperature of 35°C can also be recommended when the medium vermiculite substrate is used. In the alternating temperature of 20-30°C, the substrates blotting paper, medium and fine vermiculite can all be indicated for seed germination test of the studied species. The optimal sowing depths for P. reticulata seeds are 1.0, 1.5 and 2.0 cm.