Ecofisiologia de sementes de Piptadenia stipulacea (Benth.) Ducke

Abstract

Piptadenia stipulacea (Benth.) Ducke is a typical tree of the caatinga, commonly known as jurema branca and easily found at roadsides, its wood is used in civil construction, fabrication of coal and also in forest restoration. Thus, this Research aimed to elaborate protocols on germination and vigor of P. stipulacea seeds. The experiments were carried out at the Seed Testing Laboratory from the Department of Agronomy of Federal Rural University of Pernambuco, Recife-PE. The fruits were collected from ten trees located at the experimental station of Farm Saco, which belongs to the IPA, Company of Agropecuary Research in Pernambuco, municipality of Serra Talhada, from July to August 2009 and 2010. In order to verify the effects of substrate and temperature it was used the entirely randomized experimental design and the treatments distributed into factorial arrangement 8x7 (eight temperatures: the constant ones of 10,15,20,25,30,35 and 40 ºC and the alternated of 20-30 ºC and sevens substrates: vermiculite, sand, coconut fiber, sugarcane bagasse, tropstrato®, paper towel and blotting paper) with four repetitions of 25 seeds each and the averages were compared by the Scott-Knott test at 5% level of probability. The water stress was evaluated placing the seeds in the rolled paper substrate, moistened in polyethyleneglycol-6000, in the proportion of 2.5 times the weight of paper, using the following osmotic potential levels: 0; -0.05; -0.1; -0.2; -0.4; -0.6 e -0.8 MPa. In order to evaluate the saline stress, the seeds were placed in rolled paper substrate, moistened in NaCl, CaCl2 e KCl solutions in the following concentrations: 0; 25; 50; 75; 100; 150 e 200 mM. The experimental design used in the experiments of water and saline stress was entirely randomized, with four repetitions of 25 seeds each and the data was submitted to variance and polynomial regression. It was ascertained that, in order to evaluate germination and vigor of jurema branca seeds, the following combinations can be used: temperature of 20°C and coconut fiber substrate, temperature of 25°C in paper towel, and alternated temperature 20-30°C and sugarcane bagasse and vermiculite substrates. The temperature of 35°C with the tested substrates is not recommended as well as the temperature of 40°C as there was death of the embryos. The water and saline stress affects more the speed than the percentage of seeds germination, regardless of the substance used to simulate the stress. PEG 6000 and the NaCl, KCl and CaCl2 salts promoted relevant reduction in the germination and vigor of the seeds. The P. stipulacea seeds’ tolerance to saline stress simulated by NaCI is low, with maximal limit of germinability at 150 Mm and is classified as glycophyte, with low salt tolerance.