Biometria de frutos e sementes, e tolerância à dessecação e ao criocongelamento de sementes de três espécies arbóreas

Abstract

The objectives on this work were to determine the biometric characteristics from fruits and seeds, verifying the effects of reducing water content from seeds, treatment with cryoprotectant before storage in liquid nitrogen, and the way of thawing on the viability and vigor from Lafoensia pacari, Alibertia edulis and Genipa americana seeds. Fruits were collected in the municipality of Cáceres-MT and taken to the laboratory for mass measurement and fruits and seeds dimensions. Seeds of the three species were desiccated up to water contents equal 6, 8, 10, 12, 14 and 16% and these sown in substrate composed by vermiculite and sand in the ratio 1: 1 (v: v). In the study of cryostorage, the seeds were submitted in two types of cryoprotectants and two thawing ways, thus to each cryoprotectant an individual study. The concentrations of dimethylsulfoxide (DMSO) were 0, 5, 10, 15, 20 and 25% and the sucrose: 0, 0.25, 0.50, 0.75, 1.0 and 1.25 M. The seeds were immersed for 3 hours in solution and stored in liquid nitrogen for 120 hours, and then thawed in a fast way (38 ° C in 30 minutes) and a slow way (25 ° C for 4h). After seeding, we evaluated the percentage and the index on emergence speed, length, fresh matter mass and seedlings dry. The highest coefficients of variation occur for number of seeds per fruit and fresh matter mass of seed. The seeds development of L. pacari, A. edulis and G. americana are not affected by the reduction in water content up to 6%. L. pacari and G. Americana seeds must be treated with a solution of 19 and 10% on DMSO, respectively, and thawed in a slow way, A. edulis with 6% on DMSO, regardless of thawing way. L. pacari seeds must be treated with 0.92 M sucrose and thawed in a slow or fast way. In A. edulis, the percentage and emergence speed index are maximum when the seeds are thawed in a fast way without sucrose need. The fast way presents better emergence result when G. americana seeds are treated with solution of 0.67 M sucrose.