No abstract

Postharvest quality of hydroponic lettuce in greenhouse shaded with thermo-reflective and black screensQuality characteristics of leafy vegetables are affected by the duration of exposure, quality and intensity of light. This study was carried out under greenhouse conditions to evaluate the postharvest quality of hydroponic lettuce affect by thermo-reflective screens with different percentages of attenuation of solar radiation. The experiment was arranged in a 2 x 5 factorial randomized block design, with three replicates and treatments consisting of four thermoreflective screens ( 40; 50; 60 and 70% of attenuation of solar radiation) and one control with the black screen 50%. Lettuce (cv. Olinda, Crespa) plants grown in each experimental plot, represented by an individual hydroponic system, were evaluated for quality at harvest and after four days of cold storage (7.6 ± 1 ºC and 27 ± 5% UR). The over-shading caused by thermo-reflective 60 and 70% and black screen 50% affected the lettuce appearance. The plants shaded with thermo-reflective 40% showed lower mass loss after four days of storage. The shading provided by the thermoreflective and black screens did not affect the acid content, soluble solids, vitamin C and chlorophyll content of lettuce.Key words: Lactuca sativa L., mesh shading, soilless culture, storage. Considerando que a duração da exposição, a qualidade e intensidade de luz afetam as características de qualidade das hortaliças folhosas, conduziu-se um experimento, em ambiente protegido, com o objetivo de avaliar a qualidade pós-colheita da alface hidropônica, sob os efeitos das malhas de sombreamento, com diferentes percentagens de atenuação da radiação solar. O delineamento experimental foi o de blocos casualizados, no esquema fatorial 2 x 5, com três repetições, sendo os tratamentos constituídos por quatro malhas termorefletoras (40; 50; 60 e 70% de sombreamento) e uma testemunha, com malha negra 50%. Em cada parcela, representada por um sistema hidropônico individual, foi cultivada a alface (cv. Olinda, Crespa), sendo avaliada sua qualidade por ocasião da colheita e após quatro dias de armazenamento refrigerado (7,6 ± 1 ºC e 27 ± 5 % UR). Observou-se que o excesso de sombreamento, ocasionado pelas malhas termorefletoras 60 e 70% e malha negra 50%, comprometeram a aparência da alface. As plantas submetidas ao sombreamento com a malha termorefletora 40% apresentaram menor perda de massa, ao final de quatro dias de armazenamento. Os graus de sombreamento ocasionados pelas malhas termorefletoras e pela malha negra não influenciaram nos teores de ácido cítrico, sólidos solúveis, vitamina C e clorofila total da alface. Palavras-chave:Lactuca sativa L., sombreamento, cultivo hidropônico, armazenamento. 639Qualidade pós-colheita da alface hidropônica em ambiente protegido sob malhas...Rev. Ceres, Viçosa, v. 58, n.5, p. 638-644, set/out, 2011

RESUMO Objetivou-se avaliar o efeito dos danos mecânicos provocados por impacto, corte e abrasão sobre a qualidade de banana 'Prata Catarina', submetida

Brackish waters represent great potential for profitable agricultural production; however, productive usage depends on the adoption of proper cultural practices as well as a culture tolerant of salinity, which can require some restrictions related to soil and crop production. Given the lack of information pertaining to hydroponic melon culture, the objective of this study was to investigate physiological changes promoted by the use of brackish water in the preparation of the nutrient solution for melon (Cucumis melo L., cv. AF 015) growth in coconut fiber substrate under greenhouse conditions in Mossoró-RN, a semiarid region of Brazil. The experimental design was completely randomized, with 12 treatments arranged in a 4 x 3 factorial scheme, with 4 salt concentration levels (1.1 - control, 2.5, 4.0 and 5.5 dS m-1) and 3 exposition times (vegetative growth: 10-30 days after transplanting, DAT; flowering: 31 to 50 DAT; and fruiting and ripening: 51-70 DAT, which are the assessment phases of physiological maturation). Increasing salt concentrations in the nutrient solution reduced photosynthetic efficiency, stomatal conductance and transpiration, but increased the intercellular CO2 concentration in melon plants. A salt concentration in the low to intermediate range (2.5 dS m-1) resulted in the best water use efficiency by melon crops.

In Mossoró-RN, which is part of the semi-arid region of Brazil, a large part of the country’s melon production is concentrated, whose great potential is currently limited by water quality due to salt concentration. Therefore, the objective of this work was to investigate the use of saline nutritive solutions in the irrigation of greenhouse melon (Cucumis melo L. cv. Néctar) culture in coconut fiber. The experiment was carried out using a randomized block design with a 5 x 2 factorial arrangement, with four replications, where the treatments consisted of nutritivesolutions with five salinity levels (1.25 - control, 1.43, 1.86; 2.96 and 4.86 dS m-1) and for two different times to evaluate fruit quality parameters (at harvest and after 12 days of storage). Increasing the salinity in the nutrient solution reduces fruits’ mean weight, while total yield is only reduced with EC above 3.5 dS m-1. Fruit length anddiameter and peel and pulp thickness, SS and pH, decrease when submitted to nutrient solution with EC above 3.8 dS m-1. The peel and pulp thickness, pulp internal cavity, firmness, SS, pH, TA and fruit SS/TA ratio were influenced by the storage period.