Luiz Roberto Angelocci

Efeitos ambientais na capacidade fotossintética de genótipos de feijoeiro

Photosynthetic responses to daily environmental changes were studied in bean (Phaseolus vulgarisxa0L.) genotypes Carioca, Ouro Negro, and Guarumbe. Light response curves of CO2 assimilation and stomatal conductance (gs) were also evaluated under controlled (optimum) environmental condition. Under this condition, CO2 assimilation of Carioca was not saturated at 2,000 µmol m-2 s-1, whereas Guarumbe and Ouro Negro exhibited different levels of light saturation. All genotypes showed dynamic photoinhibition and reversible increase in the minimum chlorophyll fluorescence yield under natural condition, as well as lower photosynthetic capacity when compared with optimum environmental condition. Since differences in gs were not observed between natural and controlled conditions for Guarumbe and Ouro Negro, the lower photosynthetic capacity of these genotypes under natural condition seems to be caused by high temperature effects on biochemical reactions, as suggested by increased alternative electron sinks. The highest gs values of Carioca were observed at controlled condition, providing evidences that reduction of photosynthetic capacity at natural condition was due to low gs in addition to the high temperature effects on the photosynthetic apparatus. Carioca exhibited the highest photosynthetic rates under optimum environmental condition, and was more affected by daily changes of air temperature and leaf-to-air vapor pressure difference.

CONSTRUÇÃO E AVALIAÇÃO DE PSICRÔMETRO ASPIRADO DE TERMOPAR

The construction of a low cost aspirated thermocouple psychrometer made of PVC tubes is described. The instrument can easily be connected to dataloggers. The aspiration is made by fans used in microcomputers and temperatures measured with cooper-constantan thermocouples. A cotton string was used to make the wet junction. Its perfomance was evaluated in comparison to an Assman aspirated psychrometer and a Vaisala Inc. capacitive higrometer, in natural and controlled environments. The results show a good agreement between measures, allowing air vapour, relative humidity, temperature and specific humidity gradients to be determined using the proposed psychrometer.

EVAPOTRANSPIRATION AND IRRIGATION REQUIREMENTS OF A COFFEE PLANTATION IN SOUTHERN BRAZIL

Crop evapotranspiration (ETc) was measured as evaporative heat flux from a drip-irrigated coffee ( Coffea arabica ) plantation with 5-year-old trees using the Bowen ratio-energy balance technique. Crop transpiration (T) was determined with the stem heat balance method. Irrigation requirements were determined by comparing the ETc and T with reference evapotranspiration (ETo) derived from the Penman-Monteith equation and expressed as the ETc/ETo (Kc) and T/ETo (Kcb) ratios. Also, relationships were established between ETc and T and class A pan evaporation (ECA). The influence of inter-row vegetation on ETc was analysed, since the measurements were taken in a period of transition between dry-wet seasons. The average Kc value obtained was 1.00. The strong coupling of coffee plants to atmospheric conditions and high sensitivity of coffee plants to large vapour pressure deficits and air/leaf temperatures caused variations in Kcb in relation to ETo. Kcb ranged from 0.67, when ETo exceeded 4 mm d −1 , to 1.27 when ETo was less than 2 mm d −1 . When vegetation did not occupy the inter-row ground spaces, T represented about 0.87ETc, but 0.68ETc when ground vegetation filled the inter-row spaces.

Transpiration, leaf diffusive conductance, and atmospheric water demand relationship in an irrigated acid lime orchard

Realizaram-se determinacoes de condutância foliar a difusao de vapor (gl) e de transpiracao (T) em plantas de lima acida Tahiti com o uso de porometros de equilibrio dinâmico e balanco nulo, em pomar irrigado em Piracicaba, SP. O clima da regiao e do tipo subtropical. Efetuaram-se as medidas ao longo do periodo diurno, em varios dias entre fevereiro e novembro de 1998, e, em setembro e outubro, em folhas em expansao e naquelas totalmente expandidas, tanto ao sol quanto a sombra, bem como em folhas de lancamentos antigos, no interior da copa. As folhas mais antigas apresentaram valores menores de gl e de T em relacao aos outros grupos. Nos outros meses, as medidas foram feitas somente em folhas plenamente expandidas ao sol e a sombra. Os maiores valores de gl e T foram observados de fevereiro a abril. Para folhas ao sol, os valores de gl foram altos desde 8-9h ate o meio-dia, decrescendo gradualmente a tarde, com oscilacoes. Para as folhas a sombra, a variacao de gl ao longo do dia apresentou crescente aumento desde a primeira medida ate o meio-dia, chegando a valores proximos daqueles obtidos nas folhas ao sol e diminuindo a tarde. Em abril, a primeira medida realizada as 9 h mostrou baixos valores de gl e de T para as folhas ao sol e a sombra, sendo crescentes para aquelas ao sol ate o meio-dia, com decrescimo a tarde. De maio a novembro, houve uma diminuicao acentuada de gl e de T em relacao aos meses anteriores. Realizaram-se analises de regressao para estabelecer relacoes matematicas entre os valores medios de gl e de densidade de fluxo de fotons fotossinteticamente ativos, temperatura e deficit de pressao de vapor do ar. Com base nessas analises, discutem-se as causas de ocorrencia dos padroes de variacao de gl e de T observados ao longo do dia e do periodo experimental, discutindo-se o efeito de cada variavel ambiental sobre a resposta estomatica.

Estimativa do coeficiente de cultura do cafeeiro em função de variáveis climatológicas e fitotécnicas

Estimativas do Coeficiente de Cultura do CafeeiroRESUMOCom base em pesquisa realizada no cafezal do Departamento de Producao Vegetal da ESALQ,Universidade de Sao Paulo, utilizando a cultivar Mundo Novo IAC 388-17, enxertada na cultivar ApoataIAC 2258, plantada no espacamento de 2,5 m x 1,0 m (4.000 plantas.ha

Radiation balance of coffee hedgerows

A radiacao, tanto de ondas curtas como de ondas longas, absorvida por um renque de plantas de uma cultura que cobre de forma descontinua o solo, e uma variavel importante para os estudos das trocas de massa e de energia com a atmosfera. Este trabalho apresenta um dispositivo que movimenta oito saldo-radiometros dispostos em torno de um renque. O movimento de ida e volta ao longo de um trecho de um renque, permite a integracao do saldo de radiacao na superficie de um cilindro nocional de medidas, representando o balanco de radiacao (Rnc) do trecho amostrado. O equipamento apresentou um bom desempenho quando empregado em dois cafezais, mostrando potencial para a realizacao de medidas de campo, com valores medidos confiaveis. Foram obtidas boas correlacoes entre Rnc e a irradiância solar global e, tambem, entre Rnc e o saldo de radiacao medido sobre gramado e sobre o cafezal, para dados obtidos em intervalos de 15 minutos, diurnos e diarios. Uma adaptacao da Lei de Beer tambem foi avaliada para modelagem de Rnc, resultando valores superestimados em 10% em relacao aos valores integrados em 15 minutos pelo dispositivo movel , mas para os integrados no periodo diurno a concordância entre dados estimados e medidos nao foi boa.

Field determintation of young acid lime plants transpiration by the stem heat balance method

ABSTRACT: The stem heat balance method (HBM) measures sap flow (SF) in plants, and can be used toestimate daily transpiration flow. It is a powerful technique for water relations and irrigation field studies,but it has to be tested in species of particular interest. This paper discusses effectiveness of the HBM toestimate transpiration of young acid lime plants ( Citrus latifolia Tan. cv. Tahiti), grafted on citrumelo cv.Swingle ( Poncirus trifoliata Raf. x C. paradisi Macf.), in the field using commercial gauges (model SAG10-ws, Dynamax Inc., Huston), in Piracicaba, State of Sao Paulo, Brazil. SF was correlated to transpirationdetermined by weighing lysimeters and by a steady-state null-balance porometer. The mean ratio betweendaily values of SF and lysimetric measurements was practically unitary, showing a mean difference ofonly 0.05%, being the comparisons of values in periods shorter than 24 hours impaired by effect of windturbulence on lysimeters. The same occurred (mean difference of 0.38%) when SF and canopy transpirationestimated from porometer measurements were compared in 20-min periods, but transpiration tended toexceed SF in periods of higher transpiration and data dispersion was high (r

Growing degree-days for the 'Niagara Rosada' grapevine pruned in different seasons.

Plant growth and development are proportional to biological time, or the thermal time of the species, which can be defined as the integral of the temperature over time between the lower and upper temperature developmental thresholds. The objective of this study was to investigate the efficiency of the growing degree-day (GDD) approach for vines of the ‘Niagara Rosada’ cultivar pruned in winter and summer seasons, and physiological phases (mobilisation and reserve accumulation) in a humid subtropical region. The experiment was carried out on 13-year-old plants in Piracicaba, São Paulo State-Brazil, evaluating 24 production cycles, 12 from the winter pruning, and 12 from the summer pruning. The statistical design was comprised of randomised blocks, using the pruning dates as treatment: 20 July, 4 August, 19 August, and 3 September (winter); 1 February, 15 February, 2 March, and 16 March (summer). Comparison of the mean values of GDD among pruning dates was evaluated by the Tukey test, and comparison between pruning seasons was made by the F test for orthogonal contrasts, both at the 5% probability level. The results showed good agreement between the values of GDD required to complete the cycle from the winter pruning until harvest when compared with other studies performed with the same cultivar grown in the Southern and Southeastern regions of Brazil. However, there was a consistent statistical difference between GDD computed for winter and summer pruning, which allowed us to conclude that this bio-meteorological index is not sufficient to distinguish vines pruned in different seasons and physiological phases applied in humid subtropical climates.

Desempenho da sonda de dissipação térmica na medida da transpiração de plantas jovens de Lima Ácida

Because of the difficulty to quantify water consumption of a single tree, for irrigation scheduling, a series of techniques has appeared that directly measure the sap flow through the stem which can be related directly to transpiration. The objective of this work was to evaluate the performance of one of these methods, called heat dissipation probe method (HDP), in the measurement of sap flow using x91Tahitix92 lemon trees. Experiments were installed in an orchard of young trees, located in the experimental farm of irrigation of ESALQ, in Piracicaba, Sao Paulo State, Brazil. The evaluation was carried out using two weight lysimeters. The results demonstrated that the method can be used to measure the transpiration in citrus; however, the accuracy depends on theoretical concepts that should be considered and of certain corrections that should be accomplished. Those considerations as well as the advantages and disadvantages of this method are discussed in this work.

Zoneamento agroecológico para a região de Ribeirão Preto utilizando um sistema de informações geográficas

Objetivando contribuir com a metodologia de identificacao de potencialidades de uso das terras, este trabalho apresenta uma proposta de zoneamento agroecologico da quadricula de Ribeirao Preto, SP, localizada entre as coordenadas de 21o00S a 21o30S e 47o30W a 48o00W, com base em caracteristicas de solo, relevo e clima, utilizando-se de um Sistema de Informacoes Geograficas. Para caracterizar o regime termico-hidrico da area utilizou-se os dados de temperatura do ar e de chuva, de 22 localidades, referentes ao periodo de 1967 a 1996. De acordo com os criterios adotados, quanto a capacidade de uso das terras, o zoneamento identificou seis unidades de utilizacao da area: agricultura (I); agricultura (II); agricultura (III); pecuaria; agrossilvicultura e preservacao. As principais conclusoes referentes a area de estudo foram: o regime termico-hidrico e praticamente homogeneo, a vocacao dominante e para agricultura (I) representando aproximadamente 191.118 hectares, correspondentes a 66,3% da area e cerca de 82,5% das terras possuem vocacao para agropecuaria e 10,4% devem ser preservadas ou utilizadas seguindo tecnicas conservacionistas.