Fig 1.
Stress-induced growth inhibition.
Reduction of (A) stem length elongation (cm), (B) leaf fresh weight (FW) (g), and (C) leaf water content percentage (WC%), in oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Fig 2.
Degradation of photosynthetic pigments.
Leaf concentrations of (A) chlorophyll a, (B) chlorophyll b and (C) total carotenoids, in oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Table 1.
Monovalent ion contents in roots and leaves of N. oleander after 15 and 30 days of salt and water-stress treatments.
Values shown are means (n = 5) ± SE.
Fig 3.
K+/Na+ ratios, in (A) roots and (B) leaves in oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Fig 4.
Leaf contents of (A) proline (Pro), (B) glycine betaine (GB), and (C) total soluble sugars (TSS), in oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Fig 5.
Oxidative stress and non-enzymatic antioxidants.
Leaf levels of (A) malondialdehyde (MDA), (B) total phenolic compounds (TPC), and (C) total flavonoids (TF), in oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Fig 6.
Specific activities of (A) superoxide dismutase (SOD), (B) catalase (CAT), (C) ascorbate peroxidase (APX), and (D) glutathione reductase (GR), in leaves of oleander seedlings after 15 and 30 days of (1) salt treatments with the indicated NaCl concentrations, and (2) complete withholding of watering. Bars represent means with SE (n = 5). Different letters above the bars (lowercase for 15 days and capital for 30 days treatments) indicate significant differences between salt or water stress treatments, according to Tukey’s test (α = 0.05).
Fig 7.
Principal Component Analyses (PCAs).
Site score plot of the studied variables in the 15 days (green) and 30 days (red) salt stress treatments in N. oleander. PCAs included, as the analyzed variables: growth parameters, photosynthetic pigments, ions and osmolytes (A) or those related to oxidative stress and antioxidant systems (B). Symbols: FW, fresh weight; WC%, water content percentage; Chl a, chlorophyll a; Chl b, chlorophyll b; Caro, total carotenoids; Na+(r), sodium in roots; Na+(l), sodium in leaves; K+(r), potassium in roots; K+(l), potassium in leaves; Cl-(r), chloride in roots; Cl-(l), chloride in leaves; GB, glycine betaine; MDA, malondialdehyde; TPC, total phenolic compounds; TF, total flavonoids; SOD, superoxide dismutase; CAT, catalase; APX, ascorbate peroxidase; GR, glutathione reductase.