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

Abstract

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.

Assessment of the adaptive and phytoremediation potential of Miscanthus×giganteus grown in flotation tailings

“…Investigations related to Pb toxicity in different plant species have shown that it inhibits photosynthesis by causing negative effects on various components of the photosynthetic machinery; the authors detected Pb-induced distortions of chloroplast ultrastructure, obstruction of electron transport rate, decreased stomatal conductance and gas exchange, inhibition of the activities of enzymes involved in the Calvin cycle, etc. [9,[52][53][54][55].…”

Probing the Role of the Chloroplasts in Heavy Metal Tolerance and Accumulation in Euglena gracilis

“…As the difference between the accumulation of Pb by chloroplast and non-chloroplast-containing strains was not significant, chloroplasts may not greatly contribute to Pb bioaccumulation. Despite its lower toxicity, Pb has been reported to cause inhibition of the photosystem in plants, leading to swollen and deformed chloroplasts [38,39]. In the alga Chara vulgaris, Pb impaired the membrane system of chloroplasts and destroyed the thylakoid structure [40].…”

Melatonin-Nitric Oxide Crosstalk and Their Roles in the Redox Network in Plants

“…High concentrations of lead (Pb) in plants typically cause inimical changes in cell morphology, reduce cell growth, and eventually lead to cell death [96]. In maize plants exposed to Pb for 10 days, melatonin (0.05 or 0.10 mM) treatment resulted in reduced Pb toxicity and enhanced endogenous NO content.…”