Journal of Environmental Biology

Assessment of litter degradation in medicinal plants
subjected to ultraviolet-B radiation

S.B. Agrawal1* and Rima Kumari2

1Laboratory of Air Pollution & Global Climate Change, Department of Botany, Banaras Hindu University, Varanasi-221 005, India

2Department of Plant Sciences, University of Hyderabad, Hyderabad- 500 046, India

*Corresponding Author email : sbagrawal56@gmail.com

  Publication Data

 Paper received:

 12 April 2012

 Revised received:

 11 September 2012

 Re-revised received:

 05 October 2012

 Accepted:

 20 October 2012

Abstract

Litter decomposition is an important component of global carbon budget. Elevated influx of ultraviolet-B radiation (UV-B) as a consequence of depletion of stratospheric ozone (O₃) layer may affect litter decomposition directly or/ modifying the plant tissue quality. Chemical composition of plant can affect litter decomposition.  In the present study, three important medicinal plant species i.e. Acorus calamus, Ocimum sanctum and Cymbopogon citratus were exposed to two levels of supplemental UV-B (sUV₁ and sUV₂) during the growth period and examined the changes in leaf quality and degradation of leaf litters. The sUV₂ treatment (+3.6 kJ m^-2 d^-1) increased the rate of decomposition by 45% and 31% respectively; in leaf litters from O. sanctum and C. citratus, while no significant effect was noticed in A. calamus leaf litter. Higher accumulation of sclerenchymatous tissue around vascular bundles and increased concentrations of total phenols by 39 mg g^-1 probably lowered the decomposition rate; finding k value: 0.0049 g g^-1 d^-1 in leaf litters of A. calamus. The C/ N ratio was increased by 14% at sUV2 in C. citratus, whereas in O. sanctum it decreased by 13.6% after treatment. Results of the present experiment illustrates that firstly UV-B can modify the decomposition rate of leaf litter of test plant species, secondly it can alter the tissue chemistry particularly leaf phenolics, N and P concentrations strongly and thus affecting the decay rate and thirdly UV-B effects on decay rate and leaf chemistry is species specific.

Key words

Ultraviolet-B, Medicinal plants, C/N ratio, Decomposition rate

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