AOBPreview originally published online on October 7, 2006
Annals of Botany 2006 98(6):1261-1269; doi:10.1093/aob/mcl213
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-Pinene Inhibits Growth and Induces Oxidative Stress in Roots
1 Centre for Environment and Vocational Studies, Panjab University Chandigarh 160014, India
2 Department of Botany, Panjab University Chandigarh 160014, India
* For correspondence. E-mail daizybatish{at}yahoo.com
Received: 25 June 2006 Returned for revision: 15 August 2006 Accepted: 24 August 2006 Published electronically: 7 October 2006
• Background and Aims Determining the mode of action of allelochemicals is one of the challenging aspects in allelopathic studies. Recently, allelochemicals have been proposed to cause oxidative stress in target tissue and induce an antioxidant mechanism. 
-Pinene, one of the common monoterpenoids emitted from several aromatic plants including forest trees, is known for its growth-inhibitory activity. However, its mechanism of action remains unexplored. The aim of the present study was to determine the inhibitory effect of -pinene on root growth and generation of reactive oxygen species, as indicators of oxidative stress and changes in activities of antioxidant enzymes.
• Methods Effects of -pinene on early root growth were studied in five test species, Cassia occidentalis, Amaranthus viridis, Triticum aestivum, Pisum sativum and Cicer arietinum. Electrolyte leakage, lipid peroxidation, hydrogen peroxide generation, proline accumulation, and activities of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and glutathione reductase (GR) were studied in roots of C. occidentalis.
• Key Results -Pinene inhibited the radicle growth of all the test species. Exposure of C. occidentalis roots to -pinene enhanced solute leakage, and increased levels of malondialdehyde, proline and hydrogen peroxide, indicating lipid peroxidation and induction of oxidative stress. Activities of the antioxidant enzymes SOD, CAT, GPX, APX and GR were significantly elevated, thereby indicating the enhanced generation of reactive oxygen species (ROS) upon -pinene exposure. Increased levels of scavenging enzymes indicates their induction as a secondary defence mechanism in response to -pinene.
• Conclusions It is concluded that -pinene inhibits early root growth and causes oxidative damage in root tissue through enhanced generation of ROS, as indicated by increased lipid peroxidation, disruption of membrane integrity and elevated antioxidant enzyme levels.
Key words:
-Pinene, radicle growth, lipid peroxidation, hydrogen peroxide, proline content, electrolyte leakage, membrane integrity, antioxidant enzymes, oxidative damage, Cassia occidentalis