Salicylic acid priming before cadmium exposure increases wheat growth but does not uniformly reverse cadmium effects on membrane glycerolipids

Abstract

Cadmium (Cd) is an abiotic stressor negatively affecting plant growth and reducing crop productivity. The effects of Cd (25 μM) and of pre-soaking seeds with salicylic acid (SA) (500 μM) on morphological, physiological, and glycerolipid changes in two cultivars of wheat (Triticum aestivum L. 'Tosunbey' and 'Cumhuriyet') were explored. Parameters measured were length, fresh and dry biomass, Cd concentration, osmotic potential (ψ), lipid peroxidation, and polar lipid species in roots and leaves, as well as leaf chlorophyll a, carotenoids, and fv/fm. Fresh biomass of roots and leaves and leaf length were strongly depressed by Cd treatment compared to the control, but significantly increased with SA + Cd compared to Cd alone. Cd reduced leaf levels of chlorophyll a, carotenoids, and fv/fm, compared to controls. Treatment with SA + Cd increased pigment levels and fv/fm compared to Cd alone. Cd treatment led to a decrease in DW of total membrane lipids in leaves and depressed levels of monogalactosyldiacylglycerol and phosphatidic acid in leaves and roots of both cultivars. The effects of SA priming and SA + Cd treatment on lipid content and composition were cultivar-specific, suggesting that lipid metabolism may not be a primary target underlying SA remediation of the damaging effects of Cd on wheat growth and development.

Keywords: Galactolipids; Triticum aestivum, wheat; heavy metal; lipidomics; mass spectrometry; soil contamination; stress mitigation.

Fig. 1

Typical morphological performance of seedlings of wheat cultivars; (a) Triticum aestivum L. ‘Cumhuriyet’ and (b) ‘Tosunbey’ grown under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment for 10 days. Control (0); Cd, 25 μM; and SA, 100 mM. Scale bar: 1 cm.

Fig. 2

Leaf and root lengths (a), fresh (fw) and dry (dw) weights (b) in leaves and roots of two wheat cultivars grown under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Different small letters (a, b, c, and d) above columns indicate significant difference among treatments according to one‐way ANOVA at p < 0.05. The same letters indicate no difference. Bars indicate ±SD. The four treatments were compared separately for each cultivar and plant. Each bar represents the mean of a minimum of 10 seedlings.

Fig. 3

Leaf and root osmotic potential (ψ, MPa) in two wheat cultivars grown under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Different small letters (a, b, c, and d) above columns indicate significant differences among treatments according to one‐way ANOVA at p < 0.05. The same letters indicate no difference. Bars indicate ±SD. The four treatments were compared separately for each cultivar and plant. Each column is the mean of a minimum of 10 seedlings.

Fig. 4

Chlorophylls (Chl), carotenoids (Car) (a) and leaf fv/fm (b) in leaves of two wheat cultivars grown under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Different small letters (a, b, c, and d) above columns indicate significant difference among treatments according to one‐way ANOVA at p < 0.05. The same letters indicate no difference. Bars indicate ±SD. The four treatments were compared separately for each cultivar and plant. Each column is the mean of a minimum of 10 seedlings.

Fig. 5

Accumulation of Cd in leaves and roots in two wheat cultivars grown under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Different small letters (a, b, c, and d) above columns indicate significant differences among treatments according to one‐way ANOVA at p < 0.05. The same letters indicate no difference. Bars indicate ±SD of three independent biological replicates. The four treatments were compared separately for each cultivar and plant.

Fig. 6

Changes in molecular species of leaf lipids of wheat ‘Cumhuriyet’ under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Changes in molecular species of DGDG, MGDG, and PG (a), lysophospholipids (b), PC and PE (c), PI and PA (d), PS (e), and sulfoquinovosyldiacylglycerol (f). Values are means ± SD (nmol mg⁻¹ dry weight; n = 3). a, b, c and d on columns indicate significance of differences (p < 0.05) among treatments calculated by one‐way ANOVA. The same letters indicate no difference.

Fig. 7

Changes in molecular species of root lipids of wheat ‘Cumhuriyet’ under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Changes in molecular species of DGDG, MGDG, and PG (a), lysophospholipids (b), PC and PE (c), PI and PA (d), PS (e), and sulfoquinovosyldiacylglycerol (SQDG) (f). Values are means ± SD (nmol mg⁻¹ dry weight; n = 3). a, b, c and d on columns indicate significance of differences (p < 0.05) among treatments calculated by one‐way ANOVA. The same letters indicate no difference.

Fig. 8

Changes in molecular species of leaf lipids of wheat ‘Tosunbey’ under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Changes in molecular species of DGDG, MGDG, and PG (a), lysophospholipids (b), PC and PE (c), PI and PA (d), PS (e), and SQDG (f). Values are mean ± SD (nmol mg⁻¹ dry weight; n = 3). a, b, c and d on columns indicate significance of difference (p < 0.05) among treatments calculated by one‐way ANOVA. The same letters indicate no difference.

Fig. 9

Changes in molecular species of root lipids of wheat ‘Tosunbey’ under control conditions, Cd treatment, SA priming, and SA priming with Cd treatment. Changes in molecular species of DGDG, MGDG, and PG (a), lysophospholipids (b), PC and PE (c), PI and PA (d), PS (e), and sulfoquinovosyldiacylglycerol (f). Values are mean ± SD (nmol mg⁻¹ dry weight; n = 3). a, b, c and d on columns indicate significance of the difference (p < 0.05) among treatments calculated by one‐way ANOVA. The same letters indicate no difference.