A. Mirshekari; B. Madani
Abstract
Abstract Background and Objectives Papaya (Carica papaya L.) is a tropical fruit crop. The ‘Eksotika II’ is high yielding cultivar with pleasant aroma, but fruits soften ...
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Abstract Background and Objectives Papaya (Carica papaya L.) is a tropical fruit crop. The ‘Eksotika II’ is high yielding cultivar with pleasant aroma, but fruits soften quickly and lose their quality. Low calcium content causes low fruit quality and storage life. Foliar application of calcium on the fruit is significant to make the cell membrane integrity and cell wall firm and improve fruit quality. The objectives of this study were to determine the effects of calcium chloride foliar application on postharvest quality of papaya fruits. Materials and methods In order to evaluate the effect of calcium chloride (0, 0.5, 1, 1.5 and 2) on leaves, fruits and leaves + fruits of papaya, a factorial experiment based on RCBD was conducted in 2012. Calcium chloride was sprayed starting 21 days after flower anthesis and continued every two weeks for six times. Fruits were stored at 12±1 ̊C and RH=85-90% after harvest. The calcium and magnesium, respiration rate and ethylene, firmness, titratable acidity (TA), soluble solids concentration (SSC) and quality were determined 21 days after storage. Results The highest calcium content in fruits was observed with fruits and fruits + leaves sprayed treatments, while the lowest was recorded on leaves sprayed. Magnesium in peel and pulp of fruits that sprayed on fruits or fruits + leaves was lowest, while the highest was observed in leaves sprayed. Decreased in respiration rate and ethylene production were observed in fruits sprayed on fruits and fruits + leaves. The SSC was lowest in fruits + leaves treatment. Inverse results were recorded for TA. Moreover, calcium content in the peel and pulp, TA and overall quality increased when calcium chloride concentration in fruits and fruits + leaves treatments increased, While there was no effect on calcium content when applied to the leaves, but it increased TA. Discussion Results of this study showed that calcium could not transfer from leaf to fruit and vice versa in papaya. Since calcium moves in the transpiration stream, little or no subsequent translocation occurs from leaf to fruit. Unchanged ethylene production and respiration rate when calcium was applied to the leaves might be related to the immobility of calcium. Calcium was considered as a binding agent between cell walls which result in higher fruit firmness. Calcium is hypothesized to delay ripening by reducing disintegration of tissues and maintaining membrane integrity. The positive correlation might be related to magnesium and malate in fruits and malate might not be used in the process of respiration and thus increase in TA. The effect of calcium in decreasing SSC in fruits is possibly due to the decreasing respiration rate and metabolism activity that postpones ripening process.
