CHAPTER II CHAPTER II
2.5 Effect of different salinity treatment on tomato plant .1 Effect of salinity on agromorphogenic traits
2.5.2 Effect of salinity on physiological traits
Edris ci ciL (2012); reported that salinity treatment strongly affected the yield in cherry tomato. Addition of supplemental Ca and K' can ameliorate negative impact of high salinity. Small fruit development in salinity conditions could be related to disorder in water relations and decrease in photosynthetic productions (due to leaf area reduction) as well as chlorophyll content. Siddiky ci al. (2012); reported that different salinity level (2. 4. 8 and 12 dS!m) significantly affects on tomato plant height. leaf area, plant growh. yield, dry matter plant. Na and Cl accumulation in tomato tissues.. Under saline condition, all plant parameters of tomato varieties were reduced compared to the control. Plant growth. fruit number. fruit size and yield were decreased gradually with the increase of salinity levels.
Hajiboland ci al. (2010): conducted an experiment where plants treated with the arhuseular rnycorrhizal fungi Glo,nttc intraradices (+AMF) showed beneficial effect in salt condition. Tomato (Solatiurn /vcopersicum L.) cultivars Behta and Piazar were cultivated in soil without salt (EC = 0.63 dS/m). with
low (EC = 5 dS/m). or high (EC = 10 (IS/m) salinity. Growth and plant yield reduction affected by salinity can he the reason of variation in photosynthetic products translocation toward root. decrease of plant top especially leaves, partial or total enclosed of stomata. chlorophyll content. direct effect of salt on phou synthesis system and ion balance. Mycorrhization alleviated salt-induced reduction of P. Ca. and K uptake. Ca/Na and lCJa ratios were also better in
—AMP. Mycorrhization improved the net assimilation rates through both elevating stomatal conductance and protecting photoehemical processes of PSIT against salinity.
Rafat and Raliq (2009). reported that, total chlorophyll content in tomato plant proportionally decrease with the increase in salinity levels up to 0.41/0 sea sail solution (EC 5.4 dS/m). Amini and Ehsnapour (2006). studied the effect of MS and agar medium containing NaCI and sucrose on germination percentage, seedling growth. chlorophyll content. acid phosphate activity and soluble proteins in different eultivars of Lvcopersicon escu/entum Mill.(Cv. Isfahani.
Shirazy. Khozestani and Khorasani). Seeds were germinated under various mediuni. MS with sucrose, water agar with and without sucrose with different concentration of NaCI (0. 40. 80. 120 and 160 mM). Increasing salinity decrease the germination percentage and seedling dry weight. The highest germination percentage was found in cv. Isfahani and lowest in cv. Shirazy.
Chlorophyll content (Chl-a. Chl-h. and total Chi) were decreased with increasing salinity in both cv. Isilihani and Shirazy. Acid PhOsPhates activity was decreased in stem leaf while it was increased in roots. Enzyme activity was decreased on stem leaf in cv. Shirazy but increased in cv. Isfahani. Soluble proteins in roots of both cv. showed variation.
1-lajer et al. (2006); conducted an experiment to assess the effect of sea water salinity (1500, 2500 and 3500 ppm) on the growth of tomato (Lycopersicon escu/entum) cultivars (Trust. Grace and Plitz) in Saudi Arabia. The sea water salinity delayed seed germination and reduced germination percentage especially with increasing salinity level. They also I'ound that leaf area, total
chlorophyll and k contents. fresh weight of area! parts and percentage of dry weight of areal parts. as well as yield and some areal quality parameters rcsponded negatively as the salinity level increase. Al-Sobhi et al. (2005) found that chlorophyll-a and b content of tomato cultivars leaves decreased in general with the increasing sea water salinity. The highest chlorophyll content was in P11t7 cultivars leaves, while the lowest content was in the Trust cultivar leaves for plants grown under salinity stress. The chlorophyll content of leaves of different tomato cultivars decreased by NaCl stress.
Juan et al. (2005); conducted an experiment to identi!y the most reliable nutritional and biochemical indicators for improving salt tolerance in tomato.
The result showed that salt-resistant tomato cultivars were characterized by reduced uptake and foliar accumulation of Na and Cl'. increased K! uptake.
and greater synthesis of sucrose. carotenoids. and thiol groups. Akinci et al.
(2004); tested the response of tomato to salinity and concluded that increasing NaCl stress caused reduction in relative root, shoot and whole plant growth.
They also showed that salinity increase Na content and decrease the K content of tomato seedling leaves.
Dasgan ci al. (2002); worked on 55 tomato genotpcs to investigate the relationships among the salinity scale classes based on visual appearance and shoot Na accumulation. K'/Na' and Ca7 Naratios and shoot root dry weights.
Higher Na4 concentration on shoot of tomato indicated higher shoot damage.
Shoot K/Na and Ca1 Na ratios were signilicantly correlated with the salinity scale classes. The higher shoot KVNat and Ca/ Na ratios indicated lower shoot damage. Munns (2002). reported that salinity reduces the ability of plants to take up water, and this quickly causes reductions in plant growth rate. When excessive amounts of salt enter the plant. salt will eventually rise to toxic levels in the older transpiring leaves, causing premature senescence. and reduce the photosynthetic leaf area of the plant to a level that cannot sustain growth.
Higher amount of Na and Cl- accumulation in plant was the cause of salt toxicity. Salt-tolerant plants differ from salt-sensitive ones in having a low rate
of Na and Cl' transport to leaves, and the ability to compartmentalize these ions in vacuoles to prevent their build-up in cytoplasm or cell walls and thus avoid salt toxicity.
Foolad and [in (1997). conducted study on tomato and concluded that the inherent capabilities of a variety to maintain high tissue Ca' levels and to exclude Na from shoot were essential for the adaptation under salt stress environment and these features were highly heritable. Faiz et al. (1994):
reported that fruit yield and plant dry weight decreased with increasing salinity.
The concentration of N. K' and Ca decreased with shoots and fruits with increasing salinity. Johnson ci c'sL (1992): reported that low stem water potentials have an immediate and direct effect on phloeni turgor. reducing the driving force for sap flow into the fruit. Fruit diameter increased when the apoplasmic water potential gradient thvored solution flow into the fruit and fruit shrinkage occurred only when the water potential gradient was inverted.
Since fruit water potential remained relatively constant, the diurnal variation in stern water potential was sufficient to account for the correlation with changes in fruit diameter. An automated psychrometer was used to measure fruit and stern water potentials of tomato plants.
Blits and Al-Maghrahi (1991). conducted an experiment on plant under salinity srcss show succulence and xero-rnorphism e.g. NaCl caused succulence on cotton. tomato and salicomia. It cause many structural changes as smaller leaves with reduetuction in number. fewer stomata and thickening of leaf cuticles and earlier lignifications of roots. Increasing NaCI concentration in nutrient solution adversely affected tomato shoot and root. plant height. K concentration and K4 \Na ratio. Rrungnoli and Lauteri (1991). reported that growth of leaf area is inhibited by salinity in tomato plants. Acid phosphate activity was decrease in stcm leaf while it was increased in roots.
2.5.3 Effect of salinity on nutritional traits
Antioxidants like vitamin-C and lycopene with their antagonist liinctions against free radicals are very useful in protection against various biotic and abiotic stresses (Dc Pascale et UI.. 2001). From the nutritional and health points of view, tomato is characterized by high content in carotenoids (lycopene) and vitamin-C. Recent studies on tomato (Mittova et al., 2000) showed the involvement of antioxidative enzymes in the tolerance mechanism to salt stress induced by NaCI. SmidovA and lzzo (2009). evaluated the change in antioxidant content with maturation stage in tomato berries under elevated salinity conditions. The examined antioxidants were lipoic acid, vitamin C and vitamin E. It was found that in the majority ol' berries examined the content of dihydrolipoic acid, reduced ascorhate and u-tocopherol increased with maturation. Furthermore. the interplay between them was shown. These results are of great importance also from nutritional and health point of view. The data on mechanisms of the antioxidant response in tomato berries under salinity conditions are inadequate and incomplete.
Lycopene is the pigment principally responsible for the characteristic deep-red color of ripe tomato fruits and tomato products. It has attracted attention due to its biological and physicoehemical properties, especially related to its effects as a natural antioxidant. Although it has no provitamin A activity. lycopene does exhibit a physical quenching rate constant with singlet oxygen almost twice as high as that of beta-carotene. This makes its presence in the diet of considerable interest. Increasing clinical evidence supports the role of lycopene as a inicronutrient with important health benefits. because it appears to provide protection against a broad range of epithelial cancers (Shi and i.e Maguer.
2000).
Yong-Gen et al. (2009): conducted an experiment to elucidate the mechanisms, of the transport of carbohydrates into tomato fruits and the regulation of starch synthesis during fruit development in tomato plants. Tomato plants cv. Micro-
Foul exposed to high levels of salinity stress were examined. Growth with 160 mM NaCI doubled starch accumulation in tomato fruits compared to control plants during the early stages of development, and soluble sugars increased as the fruit matured. Tracer analysis with l3C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur a1er ripening. Salinity stress also up-regulated sucrose transporter expression iii source leaves and increased activity of ADP-glucose pyrophosphorylase (AGPase) in fruits during the early development stages. The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit.
Satio c/al. (2008): conducted an experiment to investigate the effects of SOnilvI NaCI in a hudroponic solution on the levels of various metabolites, including amino acids, soluble sugars. and organic acids, and on the expression level of salinity-responsive genes during fruit development. Results indicate that under salinity. brix (%). surface color density and flesh firmness of the fruit were signifleantly enhanced. whereas fruit enlargement was suppresses. Salinity stress strongly promoted glucose and amino hutyric acids. Cuartero ci al.
(2003); conducted an experiment on the effect of salinity on tomato crop and reported that salinity has increased fruit taste by increasing both sugars and ascorbic acid. but can't produce too much acid.
Flores ci al. (2003): conducted an experiment with tomato plants cv. Daniela grown in a nutrient solution containing 0. 30 and 60 mM NaCI and fertilized with 14/0. 12/2 and 10/4 NO3 INII.( niM ratio to determine the effect of salinity and nitrogen source. The increase in salinity and NH4 concentration in the nutrient solutions increased fruit quality by increasing the content of sugars.
organic acids and antioxidants. However, the increase in fruit quality was associated with a decrease in yield.
Dc Pascale et at (2001): found that increased EC leads to higher contents of Vitamin-C and total soluble solid in tomato fruits. Lycopene content increase with the increasing salinity up to 6-7 dS/m but at excessive salinity inhibition cffects may take over, resulting in reduced lycopene. Vitamin-C (ascorbic acid) content of tomato fruits increased with salinity and it was 60% higher in tomatoes grown at EC of 15.7 dS/m. compared with non-saitized controls.
(iiannakoula and Iliyas (2013) has showed in their research that the application of moderate salt stress on tomato plants can enhance lcopene and potentially other antioxidant concentrations in fruits. The increase in lycopene in response to salt stress in the tomato fruits varied from 20% to 80%. Although the specific biological mechanisms involved in increasing fruit lycopene deposition has not been clearly elucidated, evidence suggests that increasing antioxidant concentrations is a primary physiological response of the plant to salt stress.
Petersen et al. (1998): conducted an experiment with tomato plants irrigated by saline water. The NaCl-salinity enhances the lycopene concentrations up to 4-6 dS/m but restrict the lycopene concentration
or
tomato fruits at high salinity.This was probably due to a high temperature-induced inhibition of lycopene biosynthesis in tomatoes exposed to high solar radiation arising from smaller leaf area and consequently more fruits directly exposed to sunlight in salt- stressed plants. Vitamin-C content and brix percentage of tomatoes increase with the increasing salinity level of irrigation water.
From the above review of literature, it may conclude that salinity has marked effect on tomato plant growth and development with its nutritional quality as well as yield of tomato plant.