Potencial fisiológico de sementes e produção de mudas de espécies florestais ocorrentes na caatinga de Pernambuco.

Abstract

The present study aimed to generate information about the morphology of fruits, seeds, seedlings, germination phases and categories of normal and abnormal seedlings of P. bracteosa, P. gardnerian and P. pyramidalis; establish the most appropriate procedure for determining the moisture content of the seeds of the studied species; recommend pre-germination treatment to overcome dormancy of seeds of species; establish the optimum conditions of substrate temperature, photoperiod and levels of moistening of paper substrates and vermiculite for use in germination and seed vigor of the species and to evaluate the effects of different substrates, containers and shading levels on the production of seedlings of the species under study. For that were made descriptions and illustrations of the morphological characteristics of fruits, seeds, seedling and germination stages. For determination of water content was measured using the method oven at 105±3°C for 24 hours, with samples of seeds of different weights 5, 10 and 15 g and using different aluminum capsules (6 cm diameter x 5 cm height) and (8 cm diameter x 3 cm height). To break dormancy of seeds, and the control (no treatment), were performed the following treatments: soaking in water for 24 hours, soaking in water at 80ºC until it reaches room temperature; scarification n°. 100 for mass at the opposite the hilum; scarification n°. 100 for mass followed by soaking in water for 24 hours; chemical scarification with concentrated sulfuric acid for 30 seconds, 1, 5 and 10 minutes. The performance germination and vigor were also evaluated by subjecting the seeds at different temperatures and substrates. To review the photoperiod, the seeds of the species P. gardneriana, were subjected to continuous light, continuous dark, photoperiod of 12 hours light and 12 hours of dark and light and photoperiod of 8 hours light and 16 hours of dark, at constant temperature of 25ºC. In testing the germination and vigor, to evaluate the different levels of water for moistening of the substrate, the seeds of P. bracteosa were sown between a sheet of blotting paper and paper towel moistened in the substrates being equivalent to 2,0; 2,5; 3,0 and 3,5 times the weight of dry substrates. The seeds of P. bracteosa also were sown in vermiculite medium, moist equivalent of 50, 60, 70 and 80% of water holding capacity. The seedlings of the species studied were grown in nursery conditions, testing substrates are semi-fine vermiculite + manure; Tropstrato® + manure, coir dust + manure and sugarcane bagasse + manure in different containers: polyethylene bag and cartridge in different shading levels: full sunlight (0%) and ambient shading in the proportions 30%, 50% and 70%. The variables evaluated were: germination (%), first count (%), germination speed index, length of the primary root and shoot and root dry mass and shoot. The results showed that the fruit of P. bracteosa and P. gardneriana are dried, simple, kind and legume seeds of both species are stenospermics, epigeal germination and seedling phanerocotylar. For more accurate determination of moisture content of seeds of the species P. bracteosa capsules are recommended 6 x 4 cm) and 8 x 3 cm using samples of 5 or 15 g of seed; to P. gardneriana containers are the most suitable for 6 x 4 cm and 8 x 3 cm and seed samples 5, 10 and 15 g, except for sample 15 g and the container 6 x 4 cm, while for P. pyramidalis, it is recommended that the weight of the seed sample 15g and container of 6 x 4 cm. The seeds of P. bracteosa and P. pyramidalis not require the use of pre-germination treatments to overcome dormancy and chemical scarification of the seeds of P. gardneriana sulfuric acid for one minute is the most efficient method. The constant temperature of 25°C and vermiculite, and 20°C and the substrate blotting paper, and 10 and 15°C with the substrate paper towel are recommended for testing of germination and vigor of P. bracteosa. The seeds of P. gardneriana showed high germination and vigor when subjected to constant temperatures of 25 and 30ºC and plated on substrates sand and vermiculite, 20°C when kept in sugarcane bagasse and 10°C on the paper towel and the alternating temperature of 20-30ºC and coconut coir substrate. The best conditions for performance evaluation germination and vigor of P. pyramidalis are the constant temperatures of 30ºC and the mixture of sand and sugar cane bagasse, 25°C, combined with vermiculite and 20°C, along with sand and paper towels. The seeds of P. gardneriana behaved as neutral photoblastic in laboratory condition at 25ºC. The seeds of P. bracteosa kept the substrate moistened with water volume of 3,5 times the weight of blotter paper and paper towel dried showed higher vigor. The vermiculite moistened with water at 60, 70 and 80% capacity retention of the substrate can be used in the germination and vigor of P. bracteosa. For the production of seedlings of P. bracteosa should be used vermiculite substrates + manure or Tropstrato® + manure in plastic bags and kept in the greenhouse with shade screen 50%. The plastic bags combined with manure + vermiculite in a greenhouse with 30% shade screen and substrate Tropstrato® + manure in full sun environment can be recommended for seedling production P. gardneriana. The best conditions for production of seedlings of P. pyramidalis are manure + vermiculite in plastic bags and protected environment with 70% shade screen and substrate Tropstrato® + manure in tubes, kept in the greenhouse with shade screen 50%.