CHAPTER I INTRODUCTION
2.2 Salinity
2.2.1 Effects of salinity on different traits of tomato
2.2.1.3 Effect of salinity on nutritional traits
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Ca+2 were decreased in shoots. Johnson et al. (1992) reported reduction of driving force of sap flow into the fruit was due to low stem water potentials.
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higher in higher salinity condition during early fruit development, but, concentrations were reduced to < 1%, regardless of treatment at maturity stage. Higher fruit acid concentrations resulted from water deficit irrigation and from irrigation with saline water relative to the control in one year out of two. They concluded that fruit quality may be achieved in saline condition.
Lycopene as well as other ntioxidants like vitamin-C play antagonistically against biotic and abiotic. Stress induced by NaCl treatment can be eliminated by the mechanism of antioxidative enzymes as a tolerance (Mittova et al., 2000). Šmídová and Izzo (2009) conducted an experiment to determine the changes in antioxidant content with the maturity stage under different levels of salinity. He considered were lipoic acid, vitamin C and vitamin E as the antioxidants parameters. Shi and Le Maguer (2000) mentioned deep red color is produced due to the activity of lycopene which has some physio-chemical properties against salinity stress. Yong-Gen et al.
(2009) conducted an experiment to describe the mechanisms, of the transport of carbohydrates into tomato fruits and the regulation of starch synthesis during fruit development in tomato plants where he treated the tomato plants with higher salinity.
Accumulation of starch became double at 160 mM compared to control plants and with the maturity of tomato soluble sugars increased. He also reported that under salinity stress, carbohydrate accumulation is increased with the increase of salinity.
Satio et al. (2008) conducted an experiment in hydroponic system with a salinity level of 50 mM NaCl to investigate the effect of salinity on the metabolites such as amino acids, soluble sugars and organic acids. They reported that Brix%, surface color density and membrane stability index were increased with the higher salinity but fruit enlargement was suppressed. They also reported that glucose and amino butyric acids were increased in higher saline condition.
Cuartero et al. (2003) conducted an experiment to determine the effect of salinity on tomato quality. He reported that tomato taste was enhanced with the increase of salinity levels by increasing sugars and ascorbic acids.
Flores et al. (2003) conducted an experiment with tomato plants under a nutrient solution containing 0, 30 and 60 mM NaCl with 14/0, 12/2 and 10/4 NO3–/NH4+ mM ratio to determine the effect of salinity on quality of tomato. Fruit quality was
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increased with the increase of salinity and NH4+ by increasing the sugar contents, organic acids and antioxidants but yield was decreased with increase of salinity. They reported that fruit development was shortened the time of fruit set by 4 to 15%. Fruits of salt treated better than control plants but smaller in size. Compare to the control plants, percentage of dry weight, total soluble solids, and titratable acidity; content of reducing sugars, Cl1, Na+, and various pericarp pigments; and electrical conductivity of the juice were higher in fruits of saline-treated plants but the pH was lower. In case of salt treated plants, ethylene and CO2 evolution rates during ripening, as well as the activities of pectin methyl esterase, polymethylgalacturonase, and polygalacturonase;
were also higher in fruits of the saline-treated plants.
De Pascale et al. (2001) conducted an experiment an experiment with high EC value that leads to increase the vitamin C and total soluble sugars in tomato fruit. Up to the salinity level to 6-7 dS/m lycopene increased but decreased with the increase of salinity levels. Compared with non salanized plants, ascorbic acid was 60% higher in salt treated plants at EC 15.7 dS/m. Giannakoula and Iliyas (2013) conducted an experiment with the application of moderate salt stress and concluded that lycopene content with other antioxidant was enhanced with increase of salinity condition.
Lycopene varied from 20% to 80% in tomato plants grown under salinity condition that indicate that antioxidant increases with the increase of salinity level.
Petersen et al. (1998) carried out an experiment with tomato plants irrigated by different level of saline water. They mentioned that lycopene was increased with the higher salinity at 4-6 dS/m salinity level. As leaf area was smaller and sunlight increases the temperature of leaf and thus lycopene was increased. Vitamin-C content and brix% of tomatoes also increased with the increasing salinity level. Shenan et al.
(1991) conducted an experiment on tomato plants to determine the effect of irrigation cut off and salinity on tomato yield and quality. In both years the irrigation cutoff treatments had more pronounced effects on the SSC in fruit than the salinity treatments. Fruit SSC increased rapidly after irrigations were withheld in comparison to the control and the salinity from-thinning treatment. Similar patterns of SSC changes were observed in both cutoff treatments; however, for clarity, only the 75 day cutoff. Increases in SSC in the cutoff treatments relative to the control were larger in 1986. Salinity increased SSC by 8% in both years; however, marketable soluble solids
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were not significantly affected by either cutoff or salinity. Water content in fruit of plants exposed to deficit irrigation was lower than the control throughout development in 1986 and at maturity in 1985, and at maturity by salinity in 1985.
Fruit sugar, organic acid, and starch contents. At maturity, irrigation cutoff had no effect on the accumulation of hexoses on a dry-weight basis, but significantly increased hexose concentrations on a tissue-water basis relative to the control .Salinity did not significantly affect hexose accumulation on either a dry-weight or a tissue- water basis. Sucrose concentrations were below detectable levels in all treatments.
Fruit acid concentrations in the control and salinity treatments were similar and declined during the period of fruit development. The irrigation cutoff treatment increased titratable acidity levels and citrate concentrations during fruit development but not at maturity in 1986. In 1985, acidity was increased at maturity by both water deficit and saline irrigation. Malate accumulation reached levels roughly one-fifth those of citrate, but was unaffected by experimental treatment (data not shown). The starch content of fruit was unaffected by both the cutoff and salinity treatments throughout development. At maturity starch levels for all treatments had dropped to 1% fruit dry matter.
Akinci et al. (2004) carried out an experiment on salinity effect in the early stage of tomato plants. He reported that Characteristics of germination (percentage and period;
length and fresh-dry weight of radicle and hypcotyl) and seedling (length and fresh- dry weight of root, shoot and whole plant; leaf number and area based on Relative Growth Rate); Na+ and K+ content of leaf; K+/Na+ rate of leaf are affected with the salinity.