Camila Kissmann

Germinação de sementes de Stryphnodendron Mart. osmocondicionadas

RESUMO - Objetivou-se com esse trabalho avaliar a germinacao de sementes de tres especies de Stryphnodendron Mart. (Stryphnodendron adstringens (Mart.) Coville, S. obovatum Benth. e S. polyphyllum Mart.) osmocondicionadas em diferentes agentes osmoticos, nos potenciais de -1.0 MPa e -0.5 MPa. Sementes escarificadas em acido sulfurico durante 40 minutos foram condicionadas nos seguintes tratamentos: 1) PEG 6000; 2) PEG 6000 + KNO 3 , em partes iguais; 3) KNO 3 ; 4) Agua e 5) Testemunha, e incubadas em câmara de germinacao (BOD) na temperatura de 20 °C (± 2 °C) durante 0 h (controle), 6h, 12h e 24 horas, com luz continua. Para cada especie, o delineamento estatistico foi o inteiramente casualizado em esquema fatorial 5 (tratamentos de osmocondicionamento) x 4 (tempos de condicionamento) com quatro repeticoes de 20 sementes. Foram avaliados a porcentagem de germinacao (%G), indice de velocidade de germinacao (IVG), comprimento medio de raiz (CMR) e de parte aerea (CMPA), e massa fresca (MF) e seca (MS) das plântulas condicionadas a -1,0 MPa e, a %G e IVG daquelas condicionadas a -0,5 MPa. O osmocondicionamento no potencial de -1,0 MPa nao alterou significativamente o desempenho fisiologico das sementes de S. obovatum e S. polyphyllum, mas foi prejudicial ao desenvolvimento de S. adstringens. O condicionamento das sementes de S. adstringens e S. polyphyllum em potencial de -0,5 MPa promove maior %G e IVG. ABSTRACT - The objective of this study was to evaluate the germination of seeds of three species of Stryphnodendron Mart. (Stryphnodendron adstringens (Mart.) Coville, S. obovatum Benth. and S. polyphyllum Mart.) under priming in different osmotic agents, in osmotic potentials of -1.0 MPa and -0.5 MPa. Seeds scarified in concentrated sulphuric acid for 40 minutes were conditioned in the following treatments: 1) PEG 6000; 2) PEG 6000 + KNO 3 , in equal parts; 3) KNO 3 ; 4) Water and 5) Control. Afterwards, they were incubated in a germination chamber (BOD type) at a temperature of 20 °C (± 2 °C) during 0 h (control), 6 h, 12 h and 24 hours, under continuous light. For each species, the experiment was carried out in a completely randomized factorial with 5 (priming treatments) x 4 (priming time) factors and four repetitions of 20 seeds. The percentage of germination, germination speed index, length of root and aerial parts, and fresh and dry mass of seedlings obtained from seeds conditioned in -1.0 MPa osmotic potential and the %G and IGS of those conditioned at -0.5 MPa, were evaluated. Priming in the potential

Germinação e crescimento de Caesalpinia ferrea mart. Ex tul. Em diferentes substratos

Seedlings production of native species for commercial planting and for recovery of degraded areas leads to an increasing seeking for technologies that reduce costs to establish native species, as for example alternative substratum. The objective of this work was to provide better emergency of seeds and initial growth of seedlings of Caesalpinia ferrea Mart. ex Tul. plants, therefore it was tested different types of substrates, using dystroferric red latosol, clay texture - C, mixed with sand - S (0.5 dm3 of land / 0.5 dm3 of sand), adding organic fertilizer (OF) organosuper® and chemical fertilizer (CF) Yoorin® at different ratios, constituting the following substrates: 1) C+S (control); 2) C+S+OF (9.86 g dm-3); 3) C+S+OF (14.69 g dm-3); 4) C+S+OF (19.46 g dm-3), 5) S+C+CF (8.4 g dm-3). The composition earth + sand + 19.46 g dm-3 of the organic fertilizer provided better emergence of seedlings and greater Emergence Speed Index of wood-iron seedlings, presenting values of 60.4 and 0.330, respectively. Chemical fertilization increased the production of fresh and dry mass of seedlings, with values of 399.9mg and 169.8respectively, with means which did not significantly differ from the highest dose of organic fertilization.

Increased growth of Araucaria angustifolia under warm conditions is unaccompanied by increased photosynthetic performance

Key messageAlthoughA. angustifoliaoccurs in regions with subtropical climate, warm conditions do not seem to impair the growth of young plants.AbstractThe effects of increasing temperature are worth studying even in tree species from subtropical climates. Araucaria angustifolia occurs in the south and southeast of Brazil and in Argentina and its growth and success may be associated with low temperatures. We measured growth, photosynthetic parameters and the nutritional status of this plant growing under artificial warm and cool conditions. We expected growth and photosynthetic performance to increase under cool rather than warm conditions. Under high daily temperature, plants showed increased leaf area per plant, more leaves, containing more nitrogen. However, CO2 assimilation rates at light saturation were similar in plants grown under both conditions, and photosynthetic nitrogen use efficiency was 25% higher in plants under cool conditions. This may be the first report of temperature effects on the growth of this species. Despite enhancing growth in A. angustifolia, warm conditions do not directly influence photosynthetic activities, but enhance leaf area per plant allowing increased CO2 uptake.

Different approaches on seed germination to look into global warming effects on Araucaria angustifolia

Araucaria angustifolia is a key species in the South America. Trustworthiness of the forecast reduction of Araucaria forests due to the global warming requires germination studies. We simulated daily temperature oscillations based on soil temperatures observed in the summer and obtained greater germination performance as compared to when germination was studied under constant temperatures. However, A. angustifolia seeds are dispersed in the winter, and germination performances obtained either under daily temperature oscillations or constant conditions suggest that these seeds require temperatures that are higher than those we observed in its natural habitat during seed dispersal. Therefore, these seeds may not germinate immediately after dispersal in the field. Based on scientific projections, only unlikely temperature raises will lower germination performances of A. angustifolia seeds, eventually affecting its success. We propose that germination performance measured under constant temperatures must be carefully interpreted and that laboratory data intended for extrapolation to field conditions needs a more complex model, still not available.

Light environment influences the flood tolerance in Cordia americana (L.) Gottschling & J.S.Mill.

The subtropical riverine forests present a variation in soil water availability throughout the year, following precipitation seasonality. The objective of this work was to evaluate the responses of Cordia americana to different light intensities combined with soil flooding. Seedlings were acclimated to light treatments, with full sun and shade conditions. Sun and shade plants were subjected to soil flooding during periods of 10 (short) and 30 (longer) days. After 10 days, flooded plants had a higher root dry mass accumulation and soluble sugars content, regardless of the light condition. Shade plants presented higher shoot soluble sugars content in relation to the sun plants. After 30 days, a higher shoot soluble sugar content was observed in sun and shade flooded plants. In addition, a higher root soluble sugar content was also observed in sun plants under flood. Periods of short flooding, characterized in subtropical forests as from 5 to 15 days, favor the growth of shade plants and the roots sugar accumulation, fact that can explain the species distribution. However, long periods of flooding may be associated with light environment plasticity, suggesting that the sun plants present a higher flooding tolerance, directly associated with the ability to maintain the sugar content.