Fabrício de Oliveira Reis

Light as an indicator of ecological succession in brazilwood (Caesalpinia echinata Lam.)

The ecophysiological behavior of brazilwood (Caesalpinia echinata Lam.) plants was evaluated as affected by light quantity and quality. Nine-month-old plants were cultivated under 0%, 50%, and 80% artificial shading, and natural shading imposed by a closed canopy for a period of 392 days. At the end of that period growth parameters were measured, including relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf mass (SLM) and root:shoot ratio (R:S). Higher leaf area, dry mass and RGR were obtained under 50% artificial shade. Under full sunlight (0% shade), growth was satisfactory showing higher R:S and SLM. Growth was inhibited under 80% artificial and natural shading indicating that C. echinata is not pioneer-succession or climax specie. Simulating a gap, plants cultivated under artificial shade (50%) were transferred to full sunlight for an interval of 192 h, during which net photosynthesis (A), transpiration (E), stomatic conductance (gs), deficit of pressure vapor (VPDleaf-to-air) and the efficiency quantum potential of photosystem II (Fv/Fm) were analyzed. Plants transferred to full sunlight presented severe burning and abscission of the leaflets, as well as inhibition of A and of the photochemical efficiency of PSII (Fv/Fm). This observation associated with the reduced growth under full sunlight and better performance under moderate shade suggests characteristics of intermediate species.

Efeito fungitóxico do óleo essencial de aroeira da praia (Schinus terebinthifolius RADDI) sobre Colletotrichum gloeosporioides

Neste trabalho foi avaliado o efeito do oleo essencial do fruto de Schinus terebinthifolius sobre o crescimento micelial do fungo Colletotrichum gloeosporioides in vitro, e no desenvolvimento da antracnose no periodo de pos-colheita em mamoes. As diferentes concentracoes de oleo foram diluidas em Tween 80 a 8%. No experimento in vitro foram preparados meios de cultura BDA nas concentracoes de 0,05; 0,10; 0,25 e 0,50% do oleo essencial. O controle negativo foi realizado apenas com meio BDA e o controle solvente com meio BDA e Tween 80 a 8%. A inibicao do crescimento do fungo foi diretamente proporcional a quantidade do oleo e a maior inibicao encontrada foi de 79,07% na concentracao de oleo de 0,50%. No experimento in vivo os frutos do mamoeiro foram inoculados com o fungo em quatro tratamentos: com biofilme; com biofilme mais 0,50% do oleo; com fungicida Prochloraz e frutos controle. Embora o tratamento com oleo tenha sido eficiente contra o fungo, nao foi indicado comercialmente, pois apresentou valores elevados de perda de massa fresca, de firmeza, e tambem sintomas de fitotoxidade. O oleo tem propriedade antifungica contra C. gloeosporioides in vitro e in vivo, contudo, nao e recomendado para o mamao em funcao da fitotoxidez

Mancha fisiológica do mamão 'formosa': relações com o potencial hídrico do solo, o teor de sólidos solúveis totais do látex e as variáveis do clima

Em varias regioes produtoras de mamao do Brasil, tem sido observado um disturbio fisiologico nos frutos denominado de Mancha Fisiologica do Mamao (MFM). Tal disturbio pode causar significativos prejuizos ao produtor, uma vez que pode comprometer a qualidade do fruto da especie. Procurou-se buscar, neste trabalho, possiveis relacoes entre a incidencia da MFM, o potencial hidrico do solo, o teor de solidos soluveis no latex, a amplitude termica e o deficit de pressao de vapor do ar. Para tanto, num plantio comercial localizado na cidade de Sao Francisco do Itabapoana - RJ, foram monitorados o deficit de pressao de vapor do ar, o potencial hidrico do solo, o teor de solidos soluveis no latex dos frutos em duas faces do fruto (face proxima ao tronco e face oposta ao tronco) e a amplitude termica do ar. Foi verificado que nos meses que antecederam a epoca de maior incidencia da MFM, o deficit hidrico do solo acentuado (media diaria -113,6kPa nos meses de abril a julho), em associacao com menores demandas evaporativas do ar (media diaria nos meses de abril a julho 0,6kPa) e uma amplitude termica media de 11,3oC nessas mesmas epocas, contribuiu para a maior incidencia da MFM, nos meses julho a outubro.

Influence of chromium in Laguncularia racemosa (L). Gaertn f. physiology

Most studies of chromium have been realized in the sediments and in mangrove trees. However, little is known about its effect on growth and metabolism in this vegetation. L. racemosa plants were grown in solution with 20% of ionic strength of Hoagland and Arnon containing 100 mM NaCl and supplemented with 0.00, 0.05 and 0.50 mg L-1 of Cr+3. The growth, the pigments and gas exchange measurements showed no changes in response to doses of chromium. After 30 days the initiation of treatments, plants of L. racemosa had average 0.559 g of total dry weight, 1.34 mg L-1 of total chlorophyll and 7.9 µmol m-2 s-1 of A (CO2 photosynthetic assimilation). The photochemical potential efficiency was affected by the intermediate dose of 0.05 mg L-1 of Cr+3 (Fv/Fm=0.73) and it was associated with improved translocation of chromium from root to leaves. L. racemosa accumulated Cr+3 in the root, especially in the highest dose (560 mg g-1 DW) representing twenty-eight times the value obtained in control. The concentration of chromium in stem and leaves was not influenced by the tested doses. There was a reduction of fructose and sucrose in the largest dose of chromium, suggesting the drain of these carbohydrates to meet the energy demand of root absorption. The results suggest that L. racemosa owns characteristics of a chromium-tolerant species.

Relationship between sap flow and environmental variables in a microspray irrigation upon papaya tree canopy

Irrigation management and the use of plants adapted to water stress conditions have been very important to the success of plant production. It is now recognized that fine-tuning irrigation can improve crop water-use efficiency, creating positive impact on quality of products, and on cost of production. The water stress in fruit crops is generally caused by the deficit of water in the soil, in the atmosphere or in both. The environmental variables control the plant water loss. However, high values of leaf to air vapor pressure deficit (VPDleaf-to-air) can cause the stomatal closure and can reduce the transpiration process, mainly in large trees. In this experiment, it was used the heat dissipation method developed by GRANIER (1985) to sap flow measurements. The aim of this study was to determine the relationship between xylem sap flow and reference evapotranspiration (ET0) in papaya plants cultivated with and without microspray irrigation over canopy and under field conditions. It was also investigated the relationship between xylem sap flow, photosynthetic photons flux density (PPFD) and air vapor pressure deficit (VPDair) values. There was a delay between the loss of water through the leaves and the movement of water through the trunk (lag phase). From January to March, there was a better relation between xylem sap flow and VPDair, which was not observed from June to August, probably because of this lag phase. From January to March, plants cultivated with microaspersion showed an increase in xylem sap flow, in relation to plants cultivated without microaspersion when, at this stage, the ET0 was higher.