Teor de umidade e perda de viabilidade de sementes de Cynophalla flexuosa (L) J. Presi (feijão bravo).

Abstract

The present study seeks to answer the following question: What is the moisture seed content under which the loss of viability and vigor of Cynophalla flexuosa seeds post dispersion occurs? And how long after the harvesting and subsequent drying in the sun and shade do the seeds suffer compromise in viability and vigor? The hypothesis tested was that Cynophalla flexuosa seeds are recalcitrant and short-lived. Seeds were harvested and given different management to them, in April of 2015, when the spontaneous fruit opening in the trees began. Two experiments were carried out: in experiment 1 the harvested seeds remained inside the fruits for drying in the shade, and after two days were removed from the fruits, and continued in the shade. Samples were taken for moisture content and emergency determination, repeated daily. In experiment 2, the seeds were removed from the fruits on the day they were harvested, samples were taken for emergency tests and moisture content, and later placed in full sun for drying and performed tests mentioned above daily. The treatments consisted of the time, in days, after the drying of the seeds. Four replicates of 25 seeds were used for the emergency test and three replicates of 30 seeds for moisture content. The results pointed out that the critical moisture content of seeds dried in the shade was 30%, reached on the sixth day, and the lethal moisture content was 23%, on the seventh day, with emergence of 32% and 0% for the respective moisture contents. In sun-dried seeds the critical content was 27%, reached on the third day and 16% lethal on the fourth day, with emergencies of 19% and 0%, respectively. The IVE for both managements underwent changes, with the decrease of the moisture content with values of 1.24 to 0 for the seeds dried in the shade, and the dry ones in the sun of 1 to 0. The decrease in moisture content affects seedlings root growth, shoot height and total dry mass. It was found that after three days the sun dried seeds suffer compromise in viability and vigor and when shade dry, after six days. The hypothesis tested confirms that the seeds of Feijão Bravo are recalcitrant and short-lived because they lose viability if they are dehydrated.