Seed Priming with Silicon as a Potential to Increase Salt Stress Tolerance in Lathyrus odoratus

Abstract

Water shortage is a major problem limiting the expansion of green areas and landscapes. Using seawater as an alternative source of potable water is not a novel idea, but the issue of salt stress needs to be resolved. Salinity has a negative impact on growth and the aesthetic value of ornamental plants. In order to overcome these challenges, Lathyrus odoratus seeds were hydro-primed and halo-primed with silicon (Si) and silicon nanoparticles (SiNPs), and exposed to seawater levels. Seawater markedly reduced seed germination and growth of Lathyrus seedlings, but halo-priming was shown to significantly alleviate its negative effects. Broadly, SiNPs increased the germination percentage, reduced photosynthetic pigments and carbohydrates decrease, and enhanced water relations, despite having a negative effect on germination speed. Halo-priming significantly increased the proline content and the activities of certain enzymatic (SOD, APX and CAT) and nonenzymatic (phenolic and flavonoids) compounds, that positively influenced oxidative stress (lower MDA and H₂O₂ accumulation), resulting in seedlings with more salt stress tolerance. Halo-priming with Si or SiNPs enhanced the Si and K⁺ contents, and K⁺/Na⁺ ratio, associated with a reduction in Na⁺ accumulation. Generally, halo-priming with Si or SiNPs increased Lathyrus seedlings salt stress tolerance, which was confirmed using seawater treatments via improving germination percentage, seedlings growth and activation of the antioxidant machinery, which detoxifies reactive oxygen species (ROS).

Keywords: Lathyrus odoratus; SiNPs; antioxidant; proline; seawater; seed priming.

Figure 1

Effect of seed priming on germination (%) and mean germination time of Lathyrus odoratus seeds irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 2

Effect of seed priming on plant height (cm), fresh weight (g), and dry weight (g) of Lathyrus odoratus seedlings irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 3

Effect of seed priming on leaf water content (%) and relative water content (%) of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 4

Effect of seed priming on total chlorophyll (mg g⁻¹ FW) and carotenoids (mg g⁻¹ FW) contents of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 5

Effect of seed priming on carbohydrates (%) and proline (μmol g⁻¹ FW) contents of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 6

Effect of seed priming on total phenols (mg GAE g⁻¹ DW) and flavonoids (mg CAE g⁻¹ DW) contents of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 7

Effect of seed priming on MDA (mg g⁻¹ FW) and H₂O₂ (μmol g⁻¹ FW) contents of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 8

Effect of seed priming on SOD (U mg⁻¹ protein), CAT (U mg⁻¹ protein), and APX (U mg⁻¹ protein) activities of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 9

Effect of seed priming on Si (mg Kg⁻¹), Na (mmol g⁻¹ DW), K (mmol g⁻¹ DW) contents, and K/Na ratio (g) of Lathyrus odoratus leaves irrigated with seawater levels (0, 10, 20, and 30%). Data are mean value ± SE. Bars with different letters are significantly different at p ≤ 0.05 level.

Figure 10

The mechanisms involved in seed primed Lathyrus (with Si or SiNPs) for gaining salt stress tolerance.