Role of Cd and Cu on the Antioxidant Behaviour of Brachychiton populneus (Schott & Endl.) R.Br. (Sterculiaceae)

Abstract

ROLE OF CD AND CU ON THE ANTIOXIDANT

BEHAVIOUR OF BRACHYCHITON POPULNEUS

(SCHOTT & ENDL.) R. BR. (STERCULIACEAE)

Baycu, G.1* - Bakacak, S.A.1 - Rognes, S.E.2

1 Istanbul University

2 Oslo University

*Corresponding author, e-mail: gbaycu@gmail.com

Brachychiton populneus (Bottle tree) occurs naturally in southern

Australia. Young seedlings distribute resources to form a large

tap-rooted tuber that has considerable starch and water reserves,

allowing the tree to survive in the dry and hot periods of Mediterranean

environment. Brachychiton is commonly cultivated and

is hardy in a range of climates and soils. Oxidative stress is induced

by a wide range of environmental factors including drought,

heat and trace metal stresses. The aim of this study was to examine

the antioxidant behaviour of this drought tolerant plant to

trace metal toxicity. Plant seeds were collected from Cyprus Island,

which has a typical Mediterranean climate. We had some

difficulties during the germination and plant growth in hydroponic

cultures was impossible. For this reason sand & perlite cultures

were set up and plants were grown for several months in

the phytotrone conditions. The seedlings were then treated with

50-150μM Cd and 500-1500μM Cu for 2-week to investigate the

role of Cd and Cu on the activity of catalase (CAT), glutathione

reductase (GR) and guaiacol peroxidase (GPOX) in the leaves

and roots. The activity of CAT was diminished both by Cd and

Cu toxicity in the plant organs. GR activities were reduced by

both metals in the leaves except a slight increase in the low Cd

treatment. No changes in GR activity were observed in the roots.

Conversely, both Cd and Cu produced a raise in GPOX activity

in the leaves. Whereas an increase was observed with low Cd and

low Cu treatments in the roots, high Cd and high Cu reduced the

activity. GPOX could be exerting a stronger antioxidant function.

These results suggest that antioxidant behaviours may change

with various trace metal concentrations in different plant organs.