Effects of Ca-Gluconate on Fruit Firmness and Softening Enzyme Activities in Tomato using Hydroponics Systems

This study was carried out to investigate the effects of Ca-gluconate (Ca-glu) on fruit firmness and softening enzyme activities of hydroponically grown tomato (Solanium esculentum Mill.). The obtained results revealed that the rate of weight loss was markedly increased from at storage to 5 days after storage (DAS) in control, and was constantly increased until 7 DAS as 4.1% in Ca-glu treatment. Fruit firmness was more rapidly decreased in Ca-glu induced fruit compared to control. Results showed that fruit firmness in control and Ca-glu treated fruit were 0.67 and $0.95kg{\cdot}{\varphi}12mm^{-1}$, respectively. In our investigation, no difference was revealed in Hunter's 'a' value between control and Ca-glu treated fruit. Total carotenoids content of control fruit were rapidly increased while the Ca-glu treated fruit were gently increased. Lycopene content was higher ($63.3{\mu}g{\cdot}g^{-1}\;FW$) in control than Ca-glu treatment ($56.8{\mu}g{\cdot}g^{-1}\;FW$). The activity of Polygalacturonase (PG) was rapidly increased with increasing storage period as from 0.4 to 1.2 units whereas the PG activity of Ca-glu treatment was gently increased from 1 to 7 DAS, and rapidly increased from 7 to 11 DAS. However, the pectinesterase (PE) activity was rapidly increased in control fruit, when the storage period was increased, but interestingly, the Ca-glu treated fruit was slowly increased from 1 to 7 DAS, and rapidly increased 7to 11 DAS. ${\beta}$-galactosidase activity of Ca-glu induced fruit was rapidly increased from 1 to 7 DAS as from 1.6 to 3.0 units, and gently increased from 7 to 11 DAS. ${\beta}$-galactosidase activity of control were higher than Ca-glu treatment.