Abstract:

Cadmium (Cd) is one of the most important pollutants in soil, and it has attracted wide attention from scientists
because of its harm to soil ecosystem. Pot experiments were carried out to investigate the effects of different lanthanum (La)
levels (0, 10 and 20 mg/L LaCl3) on dry weights of plants, malonaldehyde (MDA) content, antioxidant enzymes activities,
Cd accumulation and chemical forms in two cucumber varieties (‘Yanbai’ and ‘Jinyou 1’) when exposed to Cd (20 mg/kg).
The results showed that activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) in leaves and roots,
and dry weights of leaves, stems, roots, fruits and whole plants of two varieties increased in the presence of exogenous LaCl3
when exposed to Cd. Effect of La on dry weights of whole plants was found to be higher in ‘Jinyou 1’ than that in’Yanbai’.
Exogenous lanthanum, which can increase antioxidant enzyme activities of leaves and roots in two cucumber varieties, may
play an important role in increasing resistance of plants to Cd and dry weights of whole plants. All chemical forms of Cd and
the total extractable Cd in fruits of the two varieties obviously decreased in LaCl3 treatments compared to the control, while
the total extractable Cd and residual Cd (FR) of two varieties deceased at first, and then increased with an increase in LaCl3
level. Cadmium contents in leaves, stems, roots and fruits of both varieties decreased by 6.0%–10.2%, 8.9%–23.5%, 4.0%–
29.2% and 32.0%–49.8% in the presence of LaCl3. Cadmium contents and accumulation of fruits from individual plants, and
total Cd contents in whole plants followed the decreasing order of ‘Jinyou 1’ > ‘Yanbai’ in the presence of LaCl3.

Key words: antagonism of lanthanum and cadmium, antioxidant enzymes, malonaldehyde, Cd accumulation, Cd fractions;cucumber varieties