Estimativa do vigor das sementes e das plântulas de Bixa orellana L

Abstract

Multiplication in such species as the achiote tree is limited, due to inadequate knowledge of the morphological and physiological characteristics of the seeds and seedlings, and the restricted methods for determining seed quality. The aim of this research was to study the suitability of the accelerated ageing test to estimate vigour in seeds of the achiote (Bixa orellana L.), relating the results of the test to the formation of seedlings and the differences in genotype of the genetic accessions. The achiote seeds, represented by four genetic accessions, and three lots, were evaluated for germination, first germination count, classification of seedling vigour, and seedling emergence (total and speed index). The accelerated ageing test evaluated a temperature of 41°C, and periods of 48, 72 and 96 hours of exposure of the seeds to a relative humidity of 100% (water) and 76% (saturated NaCl solution). The saturated solution reduces the amount of water absorbed by the achiote seeds under conditions of accelerated ageing, reducing seed deterioration, favouring uniformity of results and reducing the proliferation of fungi common in the germination of seeds of the achiote. The accelerated ageing test with water or saline solution for 72 or 96 hours is efficient in classifying the achiote seeds as to quality. The variation in the water content of the seeds should be between 23.6 and 28.9% (72 hours) and 29.7 and 32.9% (96 hours) when using water, and between 7.3 and 9.5% with the use of the NaCl solution.