Fig 1.
Schematic representation of the experimental setup comparing Cd and Cu-stressed Cucurbita pepo seedlings with unstressed controls.
Table 1.
Germination percentage (GP) and seed vigor indexes (SVIL and SVIW) of zucchini seeds (C. pepo L.) after 8 days of germination under CdCl2 and CuCl2 stress. dH2O: distilled water.
Fig 2.
Seed reserve mobilization and conversion efficiency in zucchini (C. pepo L.) seeds after 8 days of germination under CdCl2 and CuCl2 stress.
(A) Depleted seed reserve weight (SRW) and seed reserve depletion rate (SRR). (B) Seed metabolic efficiency (SME), seed material respired (SMR), and energy efficiency (EE). Values for the same parameter that do not share the same letter are significantly different at p ≤ 0.05, as determined by Fisher’s LSD test.
Table 2.
Total seedling length (TSL), hypocotyl length (HL), radicle length (RL), HL/RL ratio, total seedling dry weight (TSW), hypocotyl dry weight (HW), radicle dry weight (RW), and HW/RW ratio in zucchini seedlings (C. pepo L.) after 8 days of germination under CdCl2 and CuCl2 stress. dH₂O: distilled water.
Fig 3.
Phytotoxicity of CdCl₂ and CuCl₂ stress on (A) length [hypocotyl (HLP), radicle (RLP), and total seedling (TSLP)] and (B) dry weight [hypocotyl (HWP), radicle (RWP), and total seedling (TSWP)] in zucchini (C. pepo L.) seedlings after 8 days of germination.
Values for the same parameter that do not share the same letter are significantly different at p ≤ 0.05 (Fisher’s LSD test). dH₂O: distilled water.
Fig 4.
Visual phenotypic responses of zucchini (C. pepo) seedlings to CdCl2 and CuCl2 exposure.
Fig 5.
Biochemical content of zucchini (C. pepo L.) seedlings after 8 days of germination under CdCl2 and CuCl2 stress.
(A) Total soluble sugars content of cotyledons, (B) Protein content of cotyledons, and (C) Total soluble sugars content of embryonic axes. Values for the same parameter that are labeled with different letters are significantly different at p ≤ 0.05, as determined by Fisher’s LSD test.
Fig 6.
Principal Component Analysis (PCA) biplot of physiological and biochemical responses in Cucurbita pepo under heavy metal stress, showing relationships among measured parameters along two principal components.
Factor 1 (horizontal axis, 79.7% variance) represents the primary stress response gradient, clearly separating growth-related variables (germination percentage [GP], seed vigor indices [SVIL, SVIW], seedling lengths [TSL, HL, RL], and seedling weights [TSW, HW, RW]) from phytotoxicity indicators (length and weight phytotoxicity measures [TSLP, HLP, RLP, TSWP, HWP, RWP]). Factor 2 (vertical axis, 14.7% variance) reveals an independent metabolic adaptation axis, distinguishing biochemical parameters (seed reserve metrics [SRW, SRR, SMR], metabolic efficiency [SME, EE], and biochemical contents [SGC, PRC, SGE]) from morphological traits.
Table 3.
Correlation matrix of physiological and biochemical parameters in Cucurbita pepo under cadmium and copper stress, showing pairwise Pearson correlation coefficients (r values).