Effect of Pb concentrations in the soil on the growth characteristics of <i>Ligustrum lucidum</i> seedlings.

(a) stem diameter, (b) seedling height, and (c) dry weight. Vertical bars indicate means ± SD, n = 4. ANOVA values with different letters are significantly different (P < 0.05).</p

Ultrastructure of cells in the leaves of <i>Ligustrum lucidum</i> seedlings under different lead concentrations.

(a) 0 mg kg-1, (b, c) 200 mg kg-1, (d, e, f) 600 mg kg-1, (g, h) 1000 mg kg-1, and (I, j) 1400 mg kg-1. C, chloroplasts; CM, chloroplast envelope; CW, cell wall; N, nucleus; MB, multivesicular body; P, lipid globules; S, starch grain; T, thylakoid lamellae. Scale bars: 0.5 μm in a, e, and h; 1 μm in f; 2 μm in b, c, d, j, h, and i.</p

Linear correlations between the dry weight (DW), photosynthetic function (Pn), and their influencing factors in <i>Ligustrum lucidum</i> seedlings under lead stress.

<p>Linear correlations between the dry weight (DW), photosynthetic function (Pn), and their influencing factors in <i>Ligustrum lucidum</i> seedlings under lead stress.</p

Multiple linear regression analyses of biomass accumulation and photosynthetic functions in <i>Ligustrum lucidum</i> seedlings under lead stress conditions, considering the factors that influence the photosynthesis and chlorophyll fluorescence indices.

<p>Multiple linear regression analyses of biomass accumulation and photosynthetic functions in <i>Ligustrum lucidum</i> seedlings under lead stress conditions, considering the factors that influence the photosynthesis and chlorophyll fluorescence indices.</p

Effects of lead stress on the growth, physiology, and cellular structure of privet seedlings

<div><p>In this study, we investigated the effects of different lead (Pb) concentrations (0, 200, 600, 1000, 1400 mg kg^-1 soil) on the growth, ion enrichment in the tissues, photosynthetic and physiological characteristics, and cellular structures of privet seedlings. We observed that with the increase in the concentrations of Pb, the growth of privet seedlings was restricted, and the level of Pb ion increased in the roots, stem, and leaves of the seedlings; however, most of the ions were concentrated in the roots. Moreover, a decreasing trend was observed for chlorophyll a, chlorophyll b, total chlorophyll, net photosynthesis (Pn), transpiration rate (Tr), stomatal conductance (Gs), sub-stomatal CO₂ concentration (Ci), maximal photochemical efficiency (Fv/Fm), photochemical quenching (qP), and quantum efficiency of photosystem II (ΦPSII). In contrast, the carotene levels, minimum fluorescence (F₀), and non-photochemical quenching (qN) showed an increasing trend. Under Pb stress, the chloroplasts were swollen and deformed, and the thylakoid lamellae were gradually expanded, resulting in separation from the cell wall and eventual shrinkage of the nucleus. Using multiple linear regression analysis, we found that the content of Pb in the leaves exerted the maximum effect on the seedling growth. We observed that the decrease in photosynthetic activation energy, increase in pressure because of the excess activation energy, and decrease in the transpiration rate could result in maximum effect on the photosynthetic abilities of the seedlings under Pb stress. Our results should help in better understanding of the effects of heavy metals on plants and in assessing their potential for use in bioremediation.</p></div

Effects of lead stress on the growth, physiology, and cellular structure of privet seedlings - Fig 3

<p><b>Variations in the Contents of Total Chlorophyll (a), Chlorophyll a (b), Chlorophyll b (c), and Carotenoids (d) in <i>Ligustrum lucidum</i> Seedlings under Lead Stress.</b> Vertical bars in the figure indicate means ± SD, n = 3. Different letters indicate a significant difference at <i>P</i> < 0.05.</p

Effect of lead concentrations in the soil on the lead concentrations in <i>Ligustrum lucidum</i> seedlings.

<p>(a) root, (b) stem, (c) leaf. Vertical bars indicate means ± SD, n = 3. ANOVA values with different letters are significantly different (<i>P</i> < 0.05).</p

Effects of lead stress on the growth, physiology, and cellular structure of privet seedlings - Fig 5

<p><b>Effects of Lead Stress on the Initial fluorescence (F</b>_<b>0</b><b>; a), Maximum Photochemical Efficiency (F</b>_<b>v</b><b>/F</b>_<b>m</b><b>; b), Photochemical Quenching (qP; c), Nonphotochemical Quenching (qN; d), and Quantum Yield (ΦPSII; e) of <i>Ligustrum lucidum</i> Seedlings.</b> Vertical bars in the figure indicate means ± SD, n = 5. Different letters indicate significant differences at <i>P</i> < 0.05.</p

Effects of lead stress on the growth, physiology, and cellular structure of privet seedlings - Fig 4

<p><b>Variation in the Net Photosynthetic Rate (Pn; a), Stomatal Conductance (gs; b), Intracellular CO</b>_<b>2</b><b>Concentration (Ci; c), and Transpiration Rate (Tr; d) of <i>Ligustrum lucidum</i> Seedlings under Lead Stress.</b> Vertical bars in the figure indicate means ± SD, n = 5. Different letters indicate significant differences at <i>P</i> < 0.05.</p