Julio Marcos Filho

Avaliação do potencial fisiológico de lotes de sementes de soja

Several procedures can be used to evaluate the physiological potential of soybean seeds, but it is fundamental that reliable procedures are associated with the field performance of the seed lots. This research aimed to evaluate the physiological potential of soybean seed lots with quick tests, as well as vigor assessment, seedling field emergence and the computer image analysis system (SVIS®), to identify the most efficient procedure for classifying soybean seed lots. The physiological potential of five seed lots of BRS Valiosa RR and CD 208 was evaluated for two periods (before and after cold room storage) by the germination test (paper and sand), rapid evaluation tests (water imbibition and pH exudates), vigor tests (accelerated aging and electrical conductivity), seedling field emergence and the computer image analysis system (SVIS®). Germination (sand substrate), electrical conductivity and water imbibition tests were effective in separating the seed lots of both cultivars, but only the water imbibition test allowed classification in both evaluation periods. The water imbibition test is therefore considered as promising for evaluating physiological potential during seed production and storage.

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.

Priming of pioneer tree Guazuma ulmifolia (Malvaceae) seeds evaluated by an automated computer image analysis

Direct seeding is one of the most promising methods in restoration ecology, but low field seedling emergence from pioneer tree seeds still reduces its large scale applicability. The aim of this research was to evaluate seed priming for the pioneer tree species Guazuma ulmifolia. Priming treatments were selected based on seed hydration curves in water and in PEG 8000 solution. Seeds were primed in water for 16 h and in Polyethylene glycol - PEG 8000 (-0.8 MPa for 56 and 88 h) at 20°C to reach approximately 30% water content. Half of the seed sample of each treatment was dried back to the initial moisture content (7.2%); both dried and non-dried primed seeds as well as the unprimed seeds (control) were tested for germination (percentage and rate) and vigor (electrical conductivity of seed leachates). Seedling emergence percentage and rate were evaluated under greenhouse conditions, while seedling length and uniformity of seedling development were estimated using the automated image analysis software SVIS®. Primed seeds showed the highest physiological potential, which was mainly demonstrated by image analysis. Fresh or dried primed seeds in water for 16 h and in PEG (-0.8 MPa) for 56 h, and fresh primed seeds in PEG for 88 h, improved G. ulmifolia germination performance. It is suggested that these treatments were promising to enhance efficiency of stand establishment of this species by direct seeding in restoration ecology programs.

ASSESSMENT OF THE pHySiOlOgicAl pOTENTiAl OF bEll pEppEr SEEDS AND rElATiONSHip WiTH SEEDliNg EMErgENcE 1

3 ABSTRACT - The objective in this study was to verify the efficiency of different procedures for evaluating the physiological potential of bell pepper seed and identify its relationship with germination at different temperatures and with seedling emergence. Five seed lots each of the Reinger and Sentinel hybrids were used. Seed physiological potential was evaluated by germination, saturated salt accelerated aging (48 h/41 °C), seedling emergence (percentage and speed), and tetrazolium tests (preconditioning at 45 °C/3 h and seed staining at 45 °C/2 h). Germination (percentage and speed) on a thermogradient table at 15 °C, 18 °C, 21 °C, 25 °C and 30 °C was also evaluated the saturated salt accelerated aging and tetrazolium tests are suitable for access the physiological potential of bell pepper seeds. It was also confirmed that vigorous seed lots perform better when exposed to different temperatures during germination.