Mercury-Induced Phytotoxicity and Responses in Upland Cotton (Gossypium hirsutum L.) Seedlings

Abstract

Cotton is a potential and excellent candidate to balance both agricultural production and remediation of mercury-contained soil, as its main production fiber hardly involves into food chains. However, in cotton, there is known rarely about the tolerance and response to mercury (Hg) environments. In this study, the biochemical and physiological damages, in response to Hg concentrations (0, 1, 10, 50 and 100 µM), were investigated in upland cotton seedlings. The results on germination of cottonseeds indicated the germination rates were suppressed by high Hg levels, as the decrease of percentage was more than 10% at 1000 µM Hg. Shoots and roots’ growth were significantly inhibited over 10 µM Hg. The inhibitor rates (IR) in fresh weight were close in values between shoots and roots, whereas those in dry weight the root growth were more obviously influenced by Hg. In comparison of organs, the growth inhibition ranked as root > leaf > stem. The declining of translocation factor (TF) opposed the Hg level as even low to 0.05 at 50 µM Hg. The assimilation in terms of photosynthesis, of cotton plants, was affected negatively by Hg, as evidenced from the performances on pigments (chlorophyll a and b) and gas exchange (Intercellular CO2 concentration (Ci), CO2 assimilation rate (Pn) and stomatal conductance (Gs)). Sick phenotypes on leaf surface included small white zone, shrinking and necrosis. Membrane lipid peroxidation and leakage were Hg dose-dependent as indicated by malondialdehyde (MDA) content and relative conductivity (RC) values in leaves and roots. More than 10 µM Hg damaged antioxidant enzyme system in both leaves and roots (p < 0.05). Concludingly, 10 µM Hg post negative consequences to upland cotton plants in growth, physiology and biochemistry, whereas high phytotoxicity and damage appeared at more than 50 µM Hg concentration.

The Defensive Role of Endogenous H2S in Brassica rapa against Mercury-Selenium Combined Stress

“…Treatment with Hg alone slightly inhibited root growth ( Figure 1 A). This confirms the phytotoxic effect of Hg even at low levels [ 19 ]. Se induces phytotoxicity only at high concentrations [ 20 ].…”

Mercury Phytotoxicity and Tolerance in Three Wild Plants during Germination and Seedling Development

“…H. americanus did not show germination inhibition in the 4.0 mg/L Hg treatment, indicating a higher tolerance. Other tree and shrub species such as Gossypium hirsutum (cotton) were able to maintain 80% germination at 200 mg/kg Hg [ 43 ], and Quercus ilex did not have decreased germination at 10 mg/kg Hg, but its root length was reduced at 1.0 mg/kg Hg [ 44 ]. On the other hand, the neotropical tree Plathymenia reticulate (Fabaceae), from the Brazilian Cerrado reduced its germination by 80% when exposed to 10 −3 M HgCl 2 for 72 h [ 45 ].…”

Syntrichia caninervis adapt to mercury stress by altering submicrostructure and physiological properties in the Gurbantünggüt Desert

“…For example, Sergio et al reported that trace metal elements cause the plasmolysis and an obvious thickening of cell wall due to the harmful influences on the intracellular structure of bryophytes 40 . Vecchia et al found that most of the damage caused by trace metal elements was related to biological membrane, resulting in that the organelles with abundance in membrane structure are more vulnerable to serious damage than other structures 25 . Among many membrane-abundance organelles, chloroplasts and mitochondria may be the most severely damaged organelles by trace metal elements, because the latter hindered the division and expansion of these two organelles, as well as affected their shape and arrangement of the cystoid system 41 , 42 .…”

“…The concentration of Hg used in previous studies related to negative effects on plants ranged up to 100 µM 25 – 27 . Therefore, we conducted a pre-experiment with Hg concentration gradients (0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 µM, the Hg treatment, obtained using HgCl 2 (Analytical Reagent) water (DI) solution).…”