Abstract
The impact of salinity on the physiological and biochemical parameters of tolerant (‘Bonica’) and susceptible (‘Black Beauty’) eggplant varieties (Solanum melongena L.) was determined. The results revealed that the increase in salinity contributes to a significant decline in net photosynthesis (An) in both varieties; however, at the highest salt concentration (160 mM NaCl), the decrease in photorespiration (Rl) was less pronounced in the tolerant cultivar ‘Bonica’. Stomatal conductance (gs) was significantly reduced in ‘Black Beauty’ following exposure to 40 mM NaCl. However, gs of ‘Bonica’ was only substantially reduced at the highest level of NaCl (160 mM). In addition, a significant decrease in Chla, Chlb, total Chl, Chla/b and carotenoids (p > 0.05) was found in ‘Black Beauty’, and soluble carbohydrates accumulation and electrolyte leakage (EL) were more pronounced in ‘Black Beauty’ than in ‘Bonica’. The total phenols increase in ‘Bonica’ was 65% higher than in ‘Black Beauty’. In ‘Bonica’, the roots displayed the highest enzyme scavenging activity compared to the leaves. Salt stress contributes to a significant augmentation of root catalase and guaiacol peroxidase activities. In ‘Bonica’, the Na concentration was higher in roots than in leaves, whereas in ‘Black Beauty‘, the leaves accumulated more Na. Salt stress significantly boosted the Na/K ratio in ‘Black Beauty’, while no significant change occurred in ‘Bonica’. ACC deaminase activity was significantly higher in ‘Bonica’ than in ‘Black Beauty’.
Highlights
Salinity is one of the most serious abiotic stresses limiting plant growth and development, especially in salt-sensitive crops [1,2]
We focused on photosynthetic machinery, shoot and root mineral accumulation patterns, plant growth, and selected biochemical mechanisms involved in salt stress tolerance
Only ‘Black Beauty’ reduced its leaf water potential to levels below −2.5 MPa, while no correlation between leaf water potential and stomatal conductance was observed in ‘Bonica’. This reveals a tendency for isohydric behavior in ‘Bonica’ where a relative constant midday leaf water potential is observed, while the control of the plant water balance under increasing salt stress acts through reduced stomatal conductance
Summary
Salinity is one of the most serious abiotic stresses limiting plant growth and development, especially in salt-sensitive crops [1,2]. During the onset and development of salt stress within a plant, all major processes such as photosynthesis, protein synthesis, and energy and lipid metabolism are affected. Salt accumulation in soil solution reduces water and nutrient uptake. This leads to osmotic stress, ion toxicity, nutrient imbalances and a water deficit. The supply of carbohydrates, which are needed for cell growth, may be hampered because photosynthesis rates are usually lower in plants exposed to salinity, and especially to sodium chloride (NaCl) [5,6]
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