Abiotic Stress and Secondary

MetabolitesSridhar Gutam, PhDSenior Scientist (Plant Physiology)

ICAR Research Complex for Eastern RegionResearch Centre, Ranchi 834010

Plant Secondary Metabolites

• Sources for Pharmaceuticals (Ayurveda, Siddha and Unani).• Produced/accumulated under stress (adaptation mechanism).• Abiotic stresses

• High/low temperature• Drought (Moisture)• Soil alkalinity/Salinity• Nutrient Stress• UV Radiation

• Biotic stresses • Pathogens• Insects

Salinity Stress• Anthocyanins are reported to• Increase in tolerant plants (Prida and Das, 2004)• Decreases in sensitive plants (Daneshmand et al., 2010)

Drought Stress• Increase in Flavonoids and phenolic acids in willow

leaves (Larson, 1988).• In Hypericum brasiliense, total amount of phenolic

compounds increased under drought (de Abreu and Mazzafera, 2005).• “By deliberately applying moderate drought stress

during their cultivation, the quality of the related commodities can be enhanced significantly” - Selmar and Kleinwächter (2013).

Heavy Metal Stress• Cu2+ stimulated production of betalains in Beta

vulgaris (Trejo-Tapia et al., 2001).• Zn2+ enchanced yield of lepidine in Lepidum sativum

(Obrenovic, 1990).• AgNO3 and CdCl2 elicited overproduction of two

progane alkaloids scopolamine and hyoscyamine in Brugamansia candida (Angelova et al., 2006).

High/Low Temperature Stress

• Medicago sativa L. accumulates putrescine under low temperature stress (Hummel, 2004).• In Panax quinquefolus, storage ginsenoside

enhanced (Gera et al., 2007).

Quality of Medicinal Plants under Drought

Stress• Drought stress severe yield losses.• Medicinal plants produce higher concentrations of active

substances when grown under semi-arid conditions.• Water stress causes, stomatal closure and thus less CO2

fixation in Calvin Cycle.• This leads to decrease in consumption of NADPH+H+ -

(oversupply).• Thus shift towards highly reduced compounds –

Isoprenoids, Phenols, Alkaloids [Selmar and Kleinwächter (2013)]

Sage plants under Moisture stress

Sage plants under well-watered and drought stress. Content of essential oils monoterpene concentrations quantified for young, middle-aged, and old leaves.

Nowak et al. (2010) and Selmar and Kleinwächter (2013)

Model scheme for the drought stress-related increase of natural product biosynthesis according to Selmar and Kleinwächter (2013) and Kleinwächter and Selmar (2014).

The light energy absorbed by the photosynthetic apparatus is much higher than the energy required for the CO2 fixation. Consequently, large amounts of energy have to be dissipated via non-photochemical quenching and effective re-oxidation of NADPH+H+, e.g. via xanthophyll cycle and photorespiration.

Primary and secondary metabolites derived from carbon metabolism

Interrelationship of biosynthetic pathways leading to secondary constituents

Feasibility & Practical Applications

• Selmar and Kleinwächter (2013) have proposed to answer questions:

• What kind and which level of stress enhance the accumulation of the desired compounds without causing too high losses in biomass?

• What is required, a high concentration or a large bulk (total amount of natural products versus high concentrations in the drug)?

• Are the substances synthesized and accumulated in source or in sink tissues?

• Are the substances synthesized and accumulated in generative or vegetative organs?

• Could the accumulation also be increased by phytohormone treatments (e.g. methyl jasmonate, salicylic acid)?

• Should the stress be applied only within a certain phase of cultivation or whilst a special developmental phase in order to obtain maximal quality?

Agricultural Practices• Irrigation• Schedule• Soil slope• Ridge and furrow system• Drainage system

• Phytohormones• Methyl jasmonate

Thank You All@SridharGutamgutam2000@gmail.comsridhar.gutam@icar.gov.in