Melhoria da qualidade física e estudo da germinação de sementes de candeia (Eremanthus incanus (Less.) Less. e Eremanthus erythropappus (DC.) Mac Leish)

Abstract

Eremanthus incanus and Eremanthus erythropappus are forest tree species that present poor germination indices. This work intended to identify and suggest methods for evaluation of the physical and physiological quality of Eremanthus incanus and Eremanthus erythropappus seeds. The seeds used in these studies were collected in 2001 and 2002 years, respectively in Morro do Pilar and Lavras (E. incanus) and in Carrancas and Lavras (E. erythropappus). The seeds were dried, cleaned and kept in semi-permeable bags at cold room until the moment of the tests. To facilitate the identification of empty seeds a protocol using x-rays of the seeds combining potency of the radiation (Kv) and time of exposition to radiation (seconds) was developed. For removal of the empty seeds from the seed lot an experiment was undertaken by using a seed blower type South Dakota combining the opening of the apparatus and time. For germination studies two experiment were performed in which initially was tested the effect of temperatures and lately temperature alternation and light sensibility. For the germination tests the seeds were first passed through a blower, washed in sodium hypochlorite (1% for 10 minutes) and placed on paper in a gerbox. The first experiment was performed in a thermogradient table and the second in germinator type Mengelsdorfii. The imbibition curves were performed under the same conditions as the second part of the germination test. The radiation of 30 kv for 45 seconds allowed evaluation of the internal structures of the seeds. Separation of seeds by the blower allowed increase from 71.25 to 98.50% the percentage of seeds with embryo for E. incanus in the treatment using opening 3.0 and time of 30 seconds. For E. erythropappus there was an increase of 14.75 to 93.37% percentage of seeds with embryo at opening 6.0 by the time of 30 seconds. The germination tests showed that the seeds showed no dormancy and when empty seeds were removed from the seed lot germinability was higher. The seeds reached the maximum germination at 10 days for E. incanus and 14 for E. erythropappus and alternation of temperature (20-30o C) for 10 hours under light was the ideal condition for germination. The germination studies revealed also that germination might take place in the absence of light for both species. For both species phase I of imbibition was attained at 6 hours of imbibition and phase II at 72 hours independently of the conditions tested.