Journal of Environmental Biology

Ontogenetic changes in foliar features and psoralen content of

Psoralea corylifolia Linn. exposed to SO₂ stress

 

S.Tanvir Ali Mahmooduzzafar¹, M.Z. Abdin² and Muhammad Iqbal*¹

 

¹Department of Botany, Faculty of Science, Jamia Hamdard, New Delhi - 110 062, India

²Department of Biotechnology, Faculty of Science, Jamia Hamdard, New Delhi - 110 062, India

 

(Received: Nov 29, 2006; Revised received: August 08, 2007 ; Accepted: August 23, 2007)

 

Abstract: Field-grown Psoralea corylifolia plants were exposed to 0.5 ppm and 1.0 ppm concentrations of sulphur dioxide gas and sampled for observation at the pre-flowering, flowering and post-flowering stages of plant ontogeny. One ppm SO₂ concentration caused a significant decline in leaf number and leaf area per plant, total leaf dry weight, and the size and amount of midrib vasculature. The density and size of stomata decreased and many stomata were damaged. Interestingly, new epidermis developed over some of the damaged leaf stomata, thus showing a unique defence strategy against SO₂ stress through dedifferentiation of the epidermal cells. Decline in the concentrations of leaf chlorophylls and carotenoids in treated plants were up to 20% and 29% respectively. Stomatal conductance, intercellular CO₂ content and net photosynthetic rate lowered by over 52%, 20% and 35%, respectively, under the SO₂ stress. Concentration of psoralen, a basic linear furanocoumarin known for its use in the treatment of dermal diseases, was highest (5.32%) in seeds and lowest (0.28%) in roots. It was heavily reduced in SO₂? treated plants, the maximum decline occurring in seeds (86.70%) and leaves (56.27%). In the roots and shoots of the treated plants, it was low in pre-flowering stage, compared with the control, but showed a recovery during the post-flowering phase of plant growth.

 

Key words: Leaf vasculature, Photosynthesis, Psoralea corylifolia, Psoralen content, Sulphur dioxide

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