PHYTOCHROME CONTROLLED SEED-GERMINATION IN LIGHT INSENSITIVE SEEDS OF RAPHANUS-SATIVUS L CV REDONDO GIGANTE

Seed germination of Raphanus sativus is inhibited by light only under low water potential of the medium. Curves of fluence response to white, red and far-red lights demonstrated that the inhibition of seed germination is dependent on light irradiance being far-red light the more effective than the formers and the germination being inhibited by intermitent light indicates phytochrome involvement through the high irradiance reactions in the control of seed germination in radish seeds under water stress conditions.

Effects of microhabitat on palm seed predation in two forest fragments in southeast Brazil

The establishment of plants depends crucially on where seeds are deposited in the environment. Some authors suggest that in forest understory seed predation is lower than in gaps, and higher than at the forest edge. However, most studies have been carried out in large forest patches and very little is known about the effects of microhabitat conditions on seed predation in forest fragments. We evaluated the effects of three microhabitats (gaps, forest edge, and understory) on seed predation of two palm species (Euterpe edulis and Syagrus romanzoffiana) in two semi-deciduous forest fragments (230 and 2100 hat in southeast Brazil. Our objective was to test two hypotheses: (1) Low rodent abundance in small fragments as a result of meso-predator action levels leads to lower seed predation in small fragments. (2) Most mammal species in small fragments are generalists with respect to diet and habitat, so that seed predation is similar in different microhabitats (gaps, forest edge and understory) in the small fragment, but not in the larger one. The study community of small fragments is usually composed of generalist species (in diet and habitat aspects), so we expected the same rate of seed predation among microhabitats (gaps, forest edge and understory) in the tested smaller fragment. The experiment was carried out in the dry season (for E. edulis) and in the wet season (for S. romanzoffiana) in 1999. We conclude that post-dispersal seed predation in forest fragments can be directly connected with mammal communities, reflecting their historical and ecological aspects. (C) 2004 Elsevier SAS. All rights reserved.

Effects of maturation and scarification on seed germination of Syagrus schizophylla (Mart.) glass. (Arecaceae)

Syagrus schizophylla (Mart.) Glass. belongs to the Arecaccae family. This palm is native of Brazil and presents great potential for use in gardens and cultivation in pot. Palms species, with relatively few exceptions, can only be propagated from seeds; even so, there are no reports in the literature about the germination of this palm seeds. The seed maturity is a factor that interferes in the success of the germination process. For some species, studies showed that palm seeds germinated better when the fruits were completely ripe (showing full color) and for other, when they were with green coloration. Several species of the Arecaccae family presents physical dormancy of seeds in varied degrees, demanding treatments for improve germination. The objective of this work was to study the effects of maturation and of the scarification on seed germination of S. schizophylla. The experimental design used was a factorial 3 x 2 (3 maturation stadiums: green, half-ripe - yellow and completely ripe - red; and mechanical scarification: with and without), entirely casualized, with four replications of 15 seeds per plot. The seeds (with 32,43% of humidity) were placed in plastic boxes with sand (60% of humidity, placing water according to weight in each three days), under controlled conditions of alternated temperature of 25-35 degrees C, photoperiod of 12 hours. The percentage of germination and the speed germination index (SGI) were evaluated until 79 days. It was observed that, so much for germination percentage as for SGI, there was not significant difference for the interaction among the two factors, maturation stadium and scarification, however, there were significant differences among the maturation stadiums and between seeds scarified or not. The seeds from green fruits presented lower germination percentage and slower germination when compared with seeds from yellow or red fruits; the seeds from yellow or red fruits didn't differ statistically to each other. To seeds scarificated, independently of the maturation stadium, presented germination percentage significantly larger and the germination was significantly faster when compared with the seeds without scarification.

Criteria for peanut seed pre-conditioning for the tetrazolium test

The staining pattern of peanut (Arachis hypogaea L.) seeds with a tetrazolium solution was evaluated to determine the adequate conditions of seed quality evaluations. Three seed lots with different vigour levels and similar moisture content were pre-conditioned using the combination of five periods of time (4, 8, 12, 16 and 20 hours) and four temperatures (20, 25, 30 and 35 degrees C) and then exposed to a 1.0% tetrazolium solution for three hours. The moisture content levels of seeds conditioned for 8 hours at the temperatures of 25, 30 or 35 degrees C, for 12 hours at 20 or 25 degrees C and for 16 hours at 20 degrees C, were above 30%. In this range of moisture level, the staining in tetrazolium was clear and uniform, reflecting an appropriate conditioning of the seeds. However, under a practical point of view, the period of 16 hours at 20 degrees C showed to be the best option, since it allows to start the pre-conditioning an late afternoon of one day and submit the seeds for staining in the following morning.

Evidence of hetero-epitaxial growth of Pb(Mg1/3Nb2/3)O-3 on the BaTiO3 seed particles of a citrate solution

Citrate solution was employed in preparing Pb(Mg1/3Nb1/3)O-3 (PMN) powder from polymeric precursors. BaTiO3 particles of 600 nm average size were used as seed for growing PMN. X-ray diffraction (XRD) indicated the presence of both, pyrochlore Pb6Nb6MgO22 (P6N) and perovskite phases. Transmission electron microscopy (TEM) observations indicated that only the PMN phase has hetero-epitaxially grown on the BaTiO3 seed particles. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Study of seed-germination and etiolation of seedlings in Emilia-sonchifolia (l) dc and Emilia-fosgerbii nicolson (Asteraceae)

The germination of seeds of Emilia sonchifolia (2n) and E. fosgerbii (4n) was analysed and our results indicate that the former present light insensitive seeds and the latter germinated only under continuous white light. The germination of seeds under shade light presented no differences between both species, However under continuous white light, which maintain 70% of Pfr, the velocity of germination was greater in Emilia sonchifolia when compared to Emilia fosbergii, indicating that the threshold of 4n seeds were greater than 2n seeds. The analysis of the fluence response curves for etiolating process indicated that the process presented no differences between both species. The same was observed for the effect of the shade light in the etiolating process.

Seed dispersal and germination of Cryptocarya moschata Nees & Martius Ex Nees, Ocotea catharinensis Mez and Endlicheria paniculata (Sprengel) Macbride (Lauraceae)

Data of seed dispersal and germination of the studied species are presented, comparing both observations from the wild and nursery. Fruits were collected from Carlos Botelho State Park (24 degrees 44' to 24 degrees 03'S, 47 degrees 46' to 48 degrees 10'W), south of São Paulo State, Brazil. O. catharinensis had low germination percentage, both in the wild and in nursery, and did not tolerate seed storage at low temperature. In nursery, diaspores with removed mesocarp of E. paniculata presented greater germination than those in entire fruits. The high levels of seedling mortality beneath mother-trees of C. moschata, when in comparison to those observed to established seedlings from diaspores dispersed by muriquis (Brachyteles arachnoides E. Geoffroy 1806, Cebidae, Primates), allied to the absence of juveniles in the understory, are in accord with the escape model of Janzen-Connel. In nursery, diaspores of C. moschata dispersed by the primates had greater germination, in smaller time, than those collected from mother-trees.

Seed size and genotype effects on maize (Zea mays L.) yield under different technology levels

Final plant population in maize crop was used as a basis to identify the technology level of a given farmer. Final population of 50,000 plants/hectare was considered as an indication of a high technology level farmer; 35,000 of a medium, and 20,000 of a low technology level farmer. These populations were artificially obtained for the hybrids HT-2X, BR-201, and BR-205 from small, medium and large seeds. The results showed the triple cross hybrid HT-2X to be the most indicated for low technology level regions, due to its lesser sensitivity to variations in seed size and also to its significant outyielding of the other two hybrids. The double cross hybrids BR-201 and BR-205 exhibited much higher sensitivity to variations in seed size so that if they have to be used in a low technology region, the most recommended procedure would be to make use of the largest possible seeds. In conclusion, genotype and seed size seem to be factors capable of compensating for plant population reductions in maize crops. The more prolific hybrids and the largess seeds are more indicated for low technology level regions.

Peanut seed tegument is affected by liming and drying method

Calcium plays a fundamental role in cell division and growth, and is an important constituent of the cell wall. An increase in Ca concentration in the tegument of peanut (Arachis hypogea L.) seeds in response to lime application can affect its structure. The tegument structure can also be affected by the drying method of the seeds. The effects of lime application and drying methods as affecting the peanut seed tegument structure were studied in seeds from a field experiment conducted in Sao Manuel, São Paulo, Brazil. Peanut (cv. Botutatu, Valencia Type) was grown in presence or absence of 2.1 Mg ha(-1) of lime and dried in an oven, in shade and in the field. The tegument anatomical features were described and its structure was analysed. Pectic substances, lipidic reserves and starch accumulation were studied. The peanut tegument exhibited well differentiated exotesta, mesotesta and endotesta rich in pectates and covered by a cuticle. Tannin was not observed but there was lipid accumulation in mature teguments. Lignin was observed in the vascular bundles. Lime increased the tegument thickness and decreased the central cavity mainly in the exotesta cells when the period of seed drying was shortened. The effect of drying method upon the tegument was more noticeable in seeds grown without lime. It can be inferred that liming increased the resistance of the tegument.

Effect of fruit maturation stage and light on seed germination of Aiphanes aculeata

Despite their spiny nature, Aiphanes palms are popular as ornamentals. They can be grown in various soil conditions, but achieve fast, luxuriant growth in sheltered positions with plenty of water. Shaded conditions are the best when plants are young. The objective of this study was to evaluate the effect of fruit maturation stage and light on the germination of seeds of A. aculeata. Fruits were collected at three different maturation stages: (1) yellow, (2) red, (3) collected on the ground without the fleshy mesocarp (removed by birds and insects). The fleshy mesocarp was also removed in treatments (1) and (2). All fruits were then treated with thiram and 25 seeds per plot were seeded in trays full of sand. The treatments (2) and (3) were subdivided in two other treatments: (a) 12 h photoperiod, (b) continuous darkness. The temperature was maintained at 30 degrees C. Seed germination began 34 days after sowing. After 160 days, the final germination percentage was (1) 54,67%, (2a) 61,33%, (2b) 65,33%, (3a) 38,00% and (3b) 45,33%. The best treatment was (2) independently of the light conditions.

Embryology and seed development of Paepalanthus sect. Actinocephalus (Koern.) Ruhland (Eriocaulaceae)

The embryology and seed structure of Paepalanthus sect. Actinocephalus species were studied. The embryological and structural seed characters fit well with those of the other commelinaceous families. Within the Commelinales sensu Dahlgren, Eriocaulaceae and Xyridaceae represent two embryologically close families. In Paepalanthus sect. Actinocephalus the ovule is orthotropus, bitegmic, and tenuicellate with a micropyle formed by the inner integument. The seeds are endotestal. The outer cell layer of the testa and the outer periclinal wall of the endotesta disintegrate during development. The endotegmen is tanniniferous. The outer layer of the tegmen becomes compressed and is no longer recognizable in the mature seed. The seeds are operculate.