Showing 2 results for Principal Component Analysis
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.
Akram Oraki, Ehsan Shahbazi, Keramatollah Saeidi, Fariba Rafiei,
Volume 12, Issue 2 (10-2025)
Abstract
Objective: This study evaluated the effects of polyethylene glycol (PEG)-induced drought stress on germination traits, seedling growth, and seed vigor across 24 Nigella sativa genotypes to identify drought-tolerant and -sensitive genotypes.
Method: The experiment was a factorial arrangement based on a completely randomized design (CRD) with three replications, conducted at the Crop Physiology Laboratory of Shahrekord University. The factors comprised 24 N. sativa genotypes and five drought levels induced by PEG at osmotic potentials of 0 (distilled water, control), -0.2, -0.3, -0.4, and -0.6 MPa. Measured traits included germination percentage and rate, mean germination time, root and shoot length, seedling length, seedling fresh and dry weight, and seed vigor.
Results: Analysis of variance (ANOVA) revealed that genotype, drought, and their interaction significantly affected all germination and early seedling growth traits. The strongest positive correlations were observed between seed vigor and seedling length, seedling length and root length, and seed vigor and root length. Principal component analysis (PCA) of the nine traits identified three components with eigenvalues >1, accounting for 87.91% of the total variance. Based on the PCA biplot and Ward's hierarchical cluster analysis, the genotypes were classified into three groups: tolerant (genotypes 3, 8, 11, 24), semi-tolerant (genotypes 1, 2, 9, 12, 14, 17), and sensitive (the remaining 14). Multivariate tests (Pillai's trace, Wilks' lambda, Hotelling-Lawley trace, and Roy's largest root) confirmed highly significant differences among the three groups (p < 0.01), validating the classification robustness.
Conclusions: The findings reveal significant genetic diversity among N. sativa genotypes under drought stress. Genotypes 3, 8, 11, and 24, which showed superior germination performance, are recommended for future breeding programs. Furthermore, clustering enables the selection of parental lines with greater genetic distance (e.g., tolerant genotype 3 and sensitive genotype 5) for hybridization, facilitating the genetic analysis of drought tolerance mechanisms and supporting trait improvement efforts.
Highlights:
- Rapid, cost-effective PEG screening replaces field selection
- Root length as a reliable indicator of seed vigor
- Identifying 4 superior Nigella genotypes for drought tolerance
