RESUMO
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.
RESUMO
This study was carried out at the State University of Maranhão, São Luís, Brazil from January to November 2012. We assessed the behavior of the yam Dioscorea cayenensis Da Costa, fertilized with different rates and sources of nitrogen (N). The experimental design was randomized, with treatments in a 6 × 2 factorial design. The factors were represented by six rates of N fertilization (0, 50, 100, 150, 200, and 250 kg·ha-1) and two sources (ammonium sulfate and urea) by using four replicates. We evaluated the mean mass, commercial root yield, leaf N content, starch content in the tubers, and percentage of tubers with symptoms of nematode infection (dry and thick skins). The maximum values for the mean masses of commercial tubers were 2.5 and 1.9 kg with doses of 130 and 160 kg of N ha-1 from ammonium sulfate and urea, respectively. Doses of 130 and 154.3 kg of N ha-1 produced the maximum yields of commercial tubers of 19.7 and 14.9 t·ha-1 with ammonium sulfate and urea fertilization, respectively. The maximum levels of foliar N by using urea and ammonium sulfate were 36.5 and 29.3 g·kg-1, respectively, at a dosage of 250 kg·ha-1. The maximum starch contents of 25.7 and 28.3 % were obtained at doses of 114 and 116 kg of N ha-1 of ammonium sulfate and urea, respectively. The percentage of tubers infected with nematodes was 10% when the N source was urea and 15.6% when the source...(AU)
O trabalho foi realizado na Universidade Estadual do Maranhão, São Luís, MA, no período de janeiro a novembro de 2012, com o objetivo de avaliar o comportamento do inhame (Dioscorea cayenensis), cultivar Da Costa, adubado com fontes e doses de N. O delineamento experimental utilizado foi blocos casualizados com os tratamentos distribuídos em arranjo fatorial 6 × 2, com os fatores foram representados por seis doses de N (0, 50, 100, 150, 200 e 250 kg ha-1) e duas fontes (sulfato de amônio e ureia), em quatro repetições. Foram avaliados a massa média, produtividade comercial de túberas, teores de N foliar e amido nas túberas e percentagens de túberas com sintomas de ataque de nematóides (casca seca e casca grossa). Os máximos valores para as massas médias de túberas comerciais foram 2,5 e 1,9 kg alcançados nas doses de 130 e 160 kg ha-1 de N, fonte sulfato de amônio e ureia, respectivamente. As doses de 130,0 e 154,3 kg ha-1 de N foram responsáveis pelas produtividades máximas de túberas comerciais de 19,7 e 14,9 t ha-1, respectivamente, nas fontes sulfato de amônio e ureia. Os teores máximos de N foliar nas fontes ureia e sulfato de amônio foram respectivamente, de 36,5 e 29,3 g kg-1 na dose de 250 kg ha-1. Os teores máximos de amido de 25,7 e 28,3% foram obtidos nas doses de 114 e 116 kg ha-1 de N, respectivamente, nas fontes sulfato de amônio e ureia. A percentagem de...(AU)
Assuntos
Dioscorea/efeitos dos fármacos , Dioscorea/crescimento & desenvolvimento , Nitrogênio/administração & dosagemRESUMO
This study was carried out at the State University of Maranhão, São Luís, Brazil from January to November 2012. We assessed the behavior of the yam Dioscorea cayenensis Da Costa, fertilized with different rates and sources of nitrogen (N). The experimental design was randomized, with treatments in a 6 × 2 factorial design. The factors were represented by six rates of N fertilization (0, 50, 100, 150, 200, and 250 kg·ha-1) and two sources (ammonium sulfate and urea) by using four replicates. We evaluated the mean mass, commercial root yield, leaf N content, starch content in the tubers, and percentage of tubers with symptoms of nematode infection (dry and thick skins). The maximum values for the mean masses of commercial tubers were 2.5 and 1.9 kg with doses of 130 and 160 kg of N ha-1 from ammonium sulfate and urea, respectively. Doses of 130 and 154.3 kg of N ha-1 produced the maximum yields of commercial tubers of 19.7 and 14.9 t·ha-1 with ammonium sulfate and urea fertilization, respectively. The maximum levels of foliar N by using urea and ammonium sulfate were 36.5 and 29.3 g·kg-1, respectively, at a dosage of 250 kg·ha-1. The maximum starch contents of 25.7 and 28.3 % were obtained at doses of 114 and 116 kg of N ha-1 of ammonium sulfate and urea, respectively. The percentage of tubers infected with nematodes was 10% when the N source was urea and 15.6% when the source...
O trabalho foi realizado na Universidade Estadual do Maranhão, São Luís, MA, no período de janeiro a novembro de 2012, com o objetivo de avaliar o comportamento do inhame (Dioscorea cayenensis), cultivar Da Costa, adubado com fontes e doses de N. O delineamento experimental utilizado foi blocos casualizados com os tratamentos distribuídos em arranjo fatorial 6 × 2, com os fatores foram representados por seis doses de N (0, 50, 100, 150, 200 e 250 kg ha-1) e duas fontes (sulfato de amônio e ureia), em quatro repetições. Foram avaliados a massa média, produtividade comercial de túberas, teores de N foliar e amido nas túberas e percentagens de túberas com sintomas de ataque de nematóides (casca seca e casca grossa). Os máximos valores para as massas médias de túberas comerciais foram 2,5 e 1,9 kg alcançados nas doses de 130 e 160 kg ha-1 de N, fonte sulfato de amônio e ureia, respectivamente. As doses de 130,0 e 154,3 kg ha-1 de N foram responsáveis pelas produtividades máximas de túberas comerciais de 19,7 e 14,9 t ha-1, respectivamente, nas fontes sulfato de amônio e ureia. Os teores máximos de N foliar nas fontes ureia e sulfato de amônio foram respectivamente, de 36,5 e 29,3 g kg-1 na dose de 250 kg ha-1. Os teores máximos de amido de 25,7 e 28,3% foram obtidos nas doses de 114 e 116 kg ha-1 de N, respectivamente, nas fontes sulfato de amônio e ureia. A percentagem de...