Role of Gibberellic Acid and Calcium Chloride in Ripening Related Biochemical Changes in Guava (Psidium guajava L.) Fruit
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Date
2016
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Publisher
CCSHAU
Abstract
During present investigations, guava fruits of cultivars L-49 and Hisar Surkha, harvested at
IG, MG, T, R and OR stage were analyzed for various physico-chemical and biochemical parameters.
TSS and sugars (total, reducing and non reducing) increased while fruit firmness and acidity decreased
during ripening. Content of cell wall components viz. NDF, ADF, hemicellulose, cellulose, lignin,
pectin and silica was maximum at MG stage and decreased thereafter. PME was maximally active at
turning stage while PG and cellulase increased continuously. ROS indices viz. LOX activity,
superoxide radical and H2O2 content increased progressively while the activities of ROS scavenging
enzymes viz. SOD, CAT, POX, APX and GR and the content of ROS scavenging metabolites viz.
ascorbate and glutathione increased initially but later on during ripening, a significant decline was
observed. However, b-carotene content decreased throughout ripening. Ethylene evolution and ACC
oxidase activity were maximum at turning stage. Pre-treatment of fruits with GA3 and CaCl2 caused
significant inhibition of cell wall degrading enzymes, activation of ROS scavenging enzymes and
reduction in ethylene evolution during storage. ACC oxidase and glutathione content were however,
not affected by treatments. PG, purified 88 fold with 35 per cent recovery, was thermostable and a
homodimer with Mr of 80 kDa. It exhibited Michaelis Menten kinetics with Km value of 0.14%. K+,
Na+ and Fe3+ ions were found to be stimulatory. However, divalent ions Ca2+, Zn2+ and Mg2+ had
inhibitory effect. The metal binding reagent EDTA and various low molecular weight polyols were
found to be inhibitory. All reducing agents namely b-ME, DTT and cysteine activated PG.
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Keywords
Guava, Ripening, Biochemical changes, Antioxidative system, Storage GA3, CaCl2, PG