Heavy metal in the environment and effect on plant physiology

Muhammad Arifin Sandhi

Masters Student, EcologyStockholm UniversitySE- 10691, Sweden

Some Real Scenario…….

Why?

• Burning Fossil fuels• Rapid Industrilization• Mining and Smelting• Sewage Sludge• Chemical fertilzers • Pesticide, herbicide residues

( Memon et al., 2001)

Review

A brief summary about heavy metals,their availibilty,uptake and distribution pathway in plants.

Changes of plant physiology as effects of metal accumulation

The BeginingIndustrial Revolutions during18th century

http://www.lessons-from-history.com/

Heavy Metal Specific gravity 5gm/cm3

Formation of Ligands based on Oxygen

Nutrients and Heavy Metals

Essentials, required for all kinds of plant.

Cu-Photosynthesis

Zn-connective between DNA binding proteins & hydrolytic enzymes

Beneficial, required by specific plant groups.

Ni-Activation of enzymes

Co- Essential for N fixation Non-essentials, not required and accumulated in plant

body due to their weak uptake control mechanism and heavy metals under this category like Cd, Hg, Cr, etc.

(Morgan, nd; Clemens et al., 2002)

Availabilty & Uptake• Persistence• Bonding of negetive (Soil) and positive

(metal) charge.• Metal binds with hydroxyl (-OH), Carboxyl

group (COOH) and phenolic group of soil and 98% metal binds with inorganic compounds.

• In terrestrial system metal ions enter in the plant through root hair > cortex and in aquatic system ,through foliage either crack on the cuticle or stomata >plasmolema.

Physiological Effects of Metal in Plants

Cellular Interactions Stored in epidermis,collencyma and vacoular

comapartment for either less metabolic activity there or further use in future.

H+ -ATPaseworks for pumping the proton in both plasma membrane and tonoplast.

Transporter proteins (in membrane) works as carrier and channels for metal transport.

These protein classfied as Phytochelatins (PC), Metallothioneinin (MT) originated from plant and animal respectively.

Proteins bind with metals and also works as a chelator.

Some organic acid helps to transport metals from root to shoot.

(Streit & Stumm, 1993)

Physiological Effects of Metal in Plants

Metabolsim Heavy metal (Ni, Cd) can produce oxidative stress as they can

work as free radicles Responce and tolerance of metal stress of plants depends on the

concentration level and on essentiality of the metal. Enzymatic activity (anti-oxidant) and production of amino acid

reflected with heavy metal exposure.

Reproduction Cd and Pb disturbance in mitotic cell division ,mitotic index. Germination rate (81-89%) and pollen tube length (89-96%)

decrease in tobacco with Hg, Ni and Cd exposure. Pectin-Calcium based pollen tube cell complexed with metal and

reduce cell elasticity. Heavy metal cause disturbance in plumela and radicale.

Physiological Effects of Metal in Plants

Photosynthesis Leaf Chlorosis and stunting. Electron transport in PS2, Phosporylation and NADPH. Reduced chlorophyll pigment and alter leaf architecture. PS1 and carotenoid pigment less disturbed.

(Striborova et al., 1987)

Hyperaccumulator Heavy metal deposited at least 1mg/g of

their DW. R. R. Brooks (1977) Metal uptake higher due to detoxification

mechanism well developed or need metal for protection from pest and pathogen.

Deposit metal in shoot, whereas accumulator deposit in root.

400 plant species, major comes from Brassicasae, Alyssum and Thlaspi genus.

Disadvantage: low biomass production. (Wittig, 1993)

Resistance Strategy of Plants

Two Kinds, Avoidence and ToleranceAviodence Metal uptake exclusion Enzymatic change Binding with cell wall and other cell components.Tolerance Binding with MT , PC Vacuole compartmentalization

Some other ways metal release from plant like volatilazation, leaf fall,decaying of bark, leaching from leaf, fluid secretion from xylem or hydrathods.

Conclusion

Metal uptake feature can be used for phytoremediation technology.

Be a solution for solving required metal deficiency of infants (Ex. Zinc).

Needs further research to understand the amount of metal in the food grain.

(Striborova et al., 1987)

Tack så mycket !