Abohassan Farhang Sardrodi, Malihe Sadeghizadeh, Ali Khatibi, Ghasemali Abdollahi Koshki, Alireza Jamali Kharanjani,
Volume 12, Issue 2 (10-2025)
Abstract
Objective: This study aimed to distinguish early stimulatory effects from inhibitory responses in basil seeds under alkaline stress (sodium carbonate).
Method: An experiment based on completely randomized design was conducted with four Na₂CO₃ levels (0, 5, 15, and 30 mM) and three replications. Germination dynamics were assessed via germination percentage (GP), germination rate (GR), and mean germination time (MGT). Post-germination growth was evaluated using seed vigor index (SVI), biomass allocation (fresh/dry weights), and total biomass index (TBI). Salt tolerance indices (STI) were calculated, and multivariate analyses (correlation heatmap and PCA) were performed.
Results: A clear hormetic response was observed. At 5 mM, TBI reached its maximum (STI.TBI = 2.28), indicating significant growth stimulation. Concentrations above 15 mM caused a sharp decline in all indices. At 30 mM, germination capacity and early growth were severely reduced, along with decreased germination rate and disrupted biomass allocation. PCA explained 97.75% of total variance and clearly differentiated treatments. The heatmap showed a strong correlation (r = 0.962) between germination rate and seedling establishment.
Conclusions: A stimulatory threshold exists at 5 mM Na₂CO₃. The transition from hormesis to toxicity occurs between 5 and 15 mM, reflecting a limited adaptability range for Damavand basil. TBI and PCA-based clustering are reliable indicators for evaluating salt tolerance. These findings emphasize the need for careful soil and water management in alkaline environments.
Highlights
- Mild sodium carbonate stress (5 mM) stimulated seedling growth in Damavand basil, confirming a hormetic response.
- PCA effectively discriminated stress levels, explaining 97.8% of total variance.
- Total Biomass Index (TBI) was identified as the most reliable indicator of alkaline stress tolerance.
- Severe stress (30 mM) impaired biomass allocation and germination kinetics, leading to poor seedling establishment.
