Effect of lead on the physiological, biochemical and ultrastructural properties of Leucaena leucocephala

Abstract

Heavy metals are characterised by a relatively high density and cause genotoxic, cytotoxic and mutagenic effects on plants, animals and humans. Lead (Pb) is one of the heavy metals that causes toxicity to plants and animals.• This experiment was conducted using a hydroponic technique to study the effects of Pb(NO 3 ) 2 on physiological, biochemical and ultrastructural characteristics in Leucaena leucocephala seedlings. Plants were grown in a growth chamber for 21 days in Hoagland's solution supplemented with 0 (control), 25, 50, 100, 300, 500 and 700 µM Pb(NO 3 ) 2 .• Shoot heights as well as root lengths decreased significantly in Pb-treated plants with 300, 500 and 700 µM. In Pb-treated plants with high Pb concentrations, photosynthesis rate (P N ), stomatal conductance (g s ) and transpiration rate (E) decreased. Total protein and carbohydrate content in Pb-treated plants with 300, 500 and 700 µM increased significantly in leaves. Moreover, in Pb-treated plants with 300, 500 and 700 µM Pb(NO 3 ) 2 , mesophyll cells had enlarged chloroplasts with disrupted thylakoid membranes associated with large starch grains. In contrast, Pb treatments with 25, 50 µM and 100 µM were not toxic to the plants. Thick sections of roots of Pb-treated plants with 300, 500 and 700 µM Pb showed distinct changes in structure of epidermal and cortical cells. Moreover, thin sections of roots of Pb-treated plants with 300, 500 and 700 µM Pb had thickened walls of xylem cells.• These results will shed more light in understanding the effects of heavy metal stress on plants.

Effects of Heavy Metals on Stomata in Plants: A Review

“…Given their direct contact with the external environment, stomata are considered to be an important apparatus for plants to adapt to environmental stress [6][7][8][9]. An increasing number of studies have shown that heavy metal exposure can cause damages in the structure and function of plant stomata, and ultimately lead to changes in plant physiology and ecology [4,[10][11][12]. Our analysis revealed an increasing interest in the study of stomata under heavy metal stress (Figure 1); the systematic understanding of the effects of heavy metals on plant stomata is still limited because research on the interactions between heavy metals and stomata is still in its infancy.…”

Spirulina platensis improves growth, oil content, and antioxidant activitiy of rosemary plant under cadmium and lead stress

“…In this respect, cadmium promoted a significant reduction in biomass production, height, root parameters, and inhibited the production and expansion of leaves in potato ( solanum tuberosum ) plants at 50 µM 11 , and inhibited growth of wheat plants by accumulation of Cd in plant tissue 36 . Pb significantly reduced shoot height, root length, and dry mass in Leucaena leucocephala seedlings at 300–700 µM Pb (NO 3 ) 2 37 . Intuitively, application of S. platensis under heavy metals stress revealed a much greater ability to promote the growth of rosemary plants compared with untreated plants.…”

“…In this connection, Cd-negatively affected plant photosynthetic enzyme activity, pigment content, leaf stomatal conductance, induced chlorophyll degradation, and disorder in grana and thylakoids arrangements, resulting in decreased photosynthesis rate, and chlorophyll content in potato plants 11 . According to 37 chlorophyll decreases in Leucaena leucocephala seedlings have been attributed to Pb (NO 3 ) 2 at 300–700 µM induced chlorophyll synthesis inhibition. In another research, stress of cadmium (10 and 40 mg kg −1 ) and lead (60 and 180 mg kg −1 ) significantly decreased chl a, chl b, chl a + b and carotenoid in Matricaria chamomilla 46 .…”

Effect of adding Silybum and Licorice Powder on Carbohydrate and Protein Concentration in Beans Grown in Soil Treated with Cobalt and Copper

“…And possibly a decrease in photosynthetic pigments as a result of the negative effects of heavy elements in the plant (AL-Rashedy, 2020). And Plants treated with heavy metals had a decrease in the rate of photosynthesis, stomata conduction and transpiration rate (Alkhatib et al, 2019) This is one of the reasons that reduce the process of carbohydrate formation. This is similar to what was found (Selvaraj, 2018) in that the exposure of black gram plants to toxic concentrations of nickel led to a decrease in the concentration of photosynthetic pigments such as chlorophyll and carotenoids due to an imbalance in cellular systems, and this negatively affects the concentration of carbohydrates, which is the main product of the photosynthesis optical.…”