Ana Dionisia da Luz Coelho Novembre

Conservação de sementes de açaí (Euterpe oleracea Mart.)

The acai palm (Euterpe oleracea Mart.), grown principally for its palm heart and highly nutritious berrys, has recalcitrant seeds which cannot be stored for long periods because they do not resist drying or low temperatures. The effects of seed moisture content and storage temperature on the maintenance of seed quality were investigated using acai palm cultivar BRS Para seeds conditioned in polyethylene bags at moisture contents of 43.4%, 37.4%, 30.3%, 26.1%, 21.0%, 15.1% and 11.9% and storage temperatures of 20 oC, 15 oC and 10 oC for 360 days, periodic samples being taken to determine moisture content, germination and vigor. At all the temperatures studied, partial drying to a water content of 37.4% did not produce any immediate effects on germination or vigor but as the water content dropped there was progressive deterioration until at 15.1% germination ceased. After 360 days, seeds with a water content of 21.0% or less did not germinate independent of storage temperature. Seeds with a water content of 43.4% stored at 20 oC remained viable for up to 270 days.

Dormancy as exaptation to protect mimetic seeds against deterioration before dispersal

BACKGROUND AND AIMSnMimetic seeds simulate the appearance of fleshy fruits and arilled seeds without producing nutritive tissues as a reward for seed dispersers. In this strategy of seed dispersal, seeds may remain attached to the mother plant for long periods after maturity, increasing their availability to naïve seed dispersers. The hypothesis that seed coat impermeability in many tropical Fabaceae with mimetic seeds serves as an exaptation to protect the seeds from deterioration and rotting while awaiting dispersal was investigated.nnnMETHODSnSeed coat impermeability was evaluated in five mimetic-seeded species of tropical Fabaceae in south-eastern Brazil (Abarema langsdorffii, Abrus precatorius, Adenanthera pavonina, Erythrina velutina and Ormosia arborea) and in Erythrina speciosa, a basal species in its genus, which has monochromatic brown seeds and no mimetic displays. Seed hardness was evaluated as a defence against accelerated ageing (humid chamber at 41 degrees C for 144 h). Seed development and physiological potential of O. arborea was evaluated and the effect of holding mature seeds in pods on the mother plant in the field for a period of 1 year under humid tropical conditions was compared with seeds stored under controlled conditions (15 degrees C and 40 % relative air humidity).nnnKEY RESULTSnAll five mimetic-seeded species, and E. speciosa, showed strong coat impermeability, which protected the seeds against deterioration in accelerated ageing. Most O. arborea seeds only became dormant 2 months after pod dehiscence. Germination of seeds after 1 year on the plant in a humid tropical climate was 56 %, compared with 80 % for seeds stored in controlled conditions (15 degrees C, 45 % relative humidity). Seedling shoot length after 1 year did not differ between seed sources.nnnCONCLUSIONSnDormancy acts in mimetic-seeded species as an exaptation to reduce seed deterioration, allowing an increase in their effective dispersal period and mitigating the losses incurred by low removal rates by naïve avian frugivores.

Características da semente em relação ao seu potencial fisiológico e a qualidade de mudas de café (Coffea arabica L.)

The main objective of this work was to evaluate the influence of arabic coffee seed characteristics in its physiological potential and overall seedling quality. The experiment described here consisted of six treatments, with four replications, in a completely random model, combined with a factorial outline (3x2). The two seed characteristics evaluated were size (3 sieves: 18/64, 20/64and 22/64) and mass (2 classes: heavy and light). The seeds were from Catuai Amarelo IAC 86 variety (Coffea arabica L.). The seed physiologic quality was evaluated by germination rate and initial population index. Seedling quality was estimated by the variables leaf area index, cotyledon leaves, plant height, stem diameter, and leaf, stem and root dry matter. The data analysis suggested that size separation although necessary is not sufficient for an appropriate selection for high seed physiologic potential and quality of seedling production. On the other hand, total mass amount, which represents a partial estimative of endosperm mass, is a fundamental characteristic to be considered. Therefore, the association of bots arabic Coffee seed size and mass aspects should be recommended as a technical procedure during seed selection process.