Effects Of Pre-Harvest Oxalic Acid Or Calcium Treatment Combined With Naphthyl Acetic Acid On The Storability Of Kiwi Fruit

Fruits and leaves of kiwi fruit (Actinidia deliciosa. cv. Bruno) were sprayed with5mmol·L-1oxalic acid (OA)+10mg·L-naphthyl acetic acid (NAA), or0.5%calcium nitrate solution+10mg·L-1NAA, or water (as control) at40days before harvest, and these treatments were applied3times at7-day intervals. The kiwi fruits were harvested and stored at room temperature (about20°C). The effects of pre-harvest treatments on cell wall metabolism and membrane lipid peroxidation in relation to storability in kiwi fruits were investigated. The main results were as follows:1. As compared to control, the both pre-harvest (OA+NAA) and (Ca+NAA) treatments significantly increased calcium content in the flesh of fruits, maintained fruit firmness, reduced fruit decay, inhibited respiratory rate and ethylene release rate, postponed the climacteric and decreased nutiient loss. In addition, these pre-harvest treatments extended the shelf life of kiwi fruits by5and3days respectively. It was suggested that these pre-harvest treatments could delay ripening process in kiwi fruits during storage.2. As compared to control, the both pre-harvest (OA+NAA) and (Ca+NAA) treatments decreased the activity of pectinesterase (PE), polygalacturonase (PG), P-galactosidase (β-Gal), cellulase (Cx) and the degradation of protopectin, and (Ca+NAA) treatment also decreased the activity of xylanase (Xyl). Moreover, these treatments increased activity of superoxide dismutase (SOD) during period of later storage, reduced peroxidase (POD) activity, malonaldehyde (MDA) content and relative electric conductivity.(Ca+NAA) treatment also decreased the activity of lipoxidase (LOX). Thus, the effects of these treatments including the inhibition of cell wall degradation and maintaining of cell membrane integrity could contribute to delaying ripening process in kiwi fruits during storage.3. The both pre-harvest (OA+NAA) and (Ca+N A A) treatments not only increased the contents of K, Ca, Mg, Fe, Zn and15kinds of amino acid in harvested fruits, but also improved the sensory quality of kiwi fruits. In addition, pre-harvest (OA+NAA) treatment did not increase OA content in the flesh of fruits.