Journal of Environmental Biology

Involvement of calcium and calmodulin in oxidative and temperature

stress of Amaranthus lividus L. during early germination

 

 

Soumen Bhattacharjee

Post Graduate Department of Botany, Hooghly Mohsin College, Chinsurah - 712 101, India

(Received: August 24, 2007; Revised received: April 24, 2008; Accepted: July 28, 2008)

 

Abstract: Both heat and chilling caused reduction in membrane protein thiol level and increased accumulation of thiobarbituric acid reactive substances in 72 hr old germinating tissues (indicators of oxidative stress) and reduced germination and early growth performances. Calcium chelator EGTA [Ethylene glycol-bis(2-aminoethylether)-N,N,N?^,N, tetra acetic acid] calcium channel blocker LaCl₃ (Lanthanum chloride) and calmodulin inhibitor TFP (trifluroperazine) aggravated these effects of heat and chilling and added calcium reversed them. Imposition of heat and chilling stress during early germination also causes accumulation of reactive oxygen species (ROS) like O₂^- and H₂O₂. Calcium treatment significantly reduced the accumulation of both the toxic ROS, while EGTA, LaCl₃ and TFP treatment enhanced the accumulation. Activities of antioxidative enzymes catalase (CAT), ascorbate peroxidase (APOX) and glutathione reductase (GR) and total thiol content decreased significantly under both heat and chilling stress in germinating Amaranthus seedlings. Seedlings raised with Ca²⁺ treatment under heat and chilling stress exhibit higher activities of CAT, GR and APOX and total thiol level than the untreated plants. EGTA, LaCl₃ and TFP treatment, on the other hand significantly reduce the activities of all anti-oxidative enzymes and total thiol level. The work clearly supports the view that Ca²⁺-signalling pathway plays significant role in limiting heat and chilling induced oxidative stress by up-regulating antioxidative defense during recovery phase of post- germination event in Amaranthus lividus.

Key words: Heat, Chilling, Germination, Calcium, Calmodulin, Oxidative stress

 

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