Ecophysiology and water use efficiency of soybean cultivars under field conditions

A wide range of soybean cultivars is available on the market and understanding the physiological response and yield of these materials is fundamental to develop new management systems. Thus, the objective of the present study was to assess ecophysiological parameters and yield of soybean cultivars under field conditions. The experiment was carried out on a farm located in the municipality of Açailândia, Maranhão, Brazil. Three commercial cultivars were used (SC1, SC2 and SC3), and gas exchanges, SPAD index, Fv/Fm, photosynthesis index (PI), instantaneous water use efficiency (WUE) and intrinsic instantaneous of the use of water (iWUE) were assessed during the vegetative (V5) and reproductive (R5) stages. In addition, the biomass and production components were obtained. A randomized complete block design was used, with three cultivars and six replications. SC2 obtained the best mean for the photochemical variables. SC2 was more efficient at both development stages in WUE, but the maximum iWUE values were obtained in SC3. The SC2 cultivar obtained the best responses in the main variables analyzed, resulting in a higher yield.

Physiological characteristics of citrus plants infested with citrus blackfly

Abstract Aleurocanthus woglumi (Ashby, 1915) is an important agricultural pest that causes yield losses of 20-80% in citrus plants by removing plant nutrients while feeding and allowing the formation of sooty mold. The objective of this study was to evaluate physiological changes in citrus plants in response to A. woglumi infestation under field conditions. The experiment was conducted in a citrus orchard in Paço do Lumiar, Maranhão, Brazil. Thirty-two citrus plants were used, including eight of each of the following varieties: Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine. Four random plants with A. woglumi infestation and four plants free from this pest were selected from each variety. The physiological parameters evaluated were photochemical efficiency and gas exchange. Regarding photochemical efficiency, infested plants presented photoinhibition damage, with a performance index of 4.22. The gas exchange parameters of infested plants changed, with reductions in photosynthetic CO2 assimilation of 69.7% (Tahiti), 64% (Tanjaroa), 68.8% (Nissey) and 63.3% (Ponkan). Plants infested with A. woglumi also presented physiological changes; their photosynthetic CO2 assimilation, stomatal conductance, instantaneous transpiration, and performance indexes were affected. The infested citrus plants showed photoinhibition of photosystem II. The photosynthetic CO2 assimilation decreased approximately 70% in Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine plants infested with A. woglumi.

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 / Skin freckles on 'Formosa' papaya: relationships with soil water potential, total soluble solids of latex and climate variables

Em várias regiões produtoras de mamão do Brasil, tem sido observado um distúrbio fisiológico nos frutos denominado de Mancha Fisiológica do Mamão (MFM). Tal distúrbio pode causar significativos prejuízos ao produtor, uma vez que pode comprometer a qualidade do fruto da espécie. Procurou-se buscar, neste trabalho, possíveis relações entre a incidência da MFM, o potencial hídrico do solo, o teor de sólidos solúveis no látex, a amplitude térmica e o déficit de pressão de vapor do ar. Para tanto, num plantio comercial localizado na cidade de São Francisco do Itabapoana - RJ, foram monitorados o déficit de pressão de vapor do ar, o potencial hídrico do solo, o teor de sólidos solúveis no látex dos frutos em duas faces do fruto (face próxima ao tronco e face oposta ao tronco) e a amplitude térmica do ar. Foi verificado que nos meses que antecederam a época de maior incidência da MFM, o déficit hídrico do solo acentuado (média diária -113,6kPa nos meses de abril a julho), em associação com menores demandas evaporativas do ar (média diária nos meses de abril a julho 0,6kPa) e uma amplitude térmica média de 11,3ºC nessas mesmas épocas, contribuiu para a maior incidência da MFM, nos meses julho a outubro.

In some papaya producing regions in Brazil, it was observed a physiological disturb in the fruits called Skin Freckles (SF). Such disturb may cause significant damages to crops, since it may affect the quality of the fruits. This work aimed to search possible relationship among the SF incidence, the soil water potential, the soluble solid content in the latex, the thermal amplitude and the air vapor pressure deficit. These studies were carried out in a commercial orchard located in the town of São Francisco de Itabapoana - RJ, where some characteristics were monitored including the air vapor pressure deficit, the soil water potential, the soluble solid content in the latex in two faces of the fruit (the face close to the trunk and the opposing face to the trunk) and the air thermal amplitude. One verified that in the months that preceeded the period of higher incidence of the SF, the soil water deficit increased (daily average of -113,6kPa from April to July), in association with smaller air evaporative demands (daily average of 0,6kPa from April to July) and a thermal amplitude average of 11,3ºC in these same periods contributed for the higher incidence of the SF in the months between July and October.