Selenium-induced protection of photosynthesis activity in rape (Brassica napus) seedlings subjected to cadmium stress. Fluorescence and EPR measurements.

Fluorescence and electron paramagnetic resonance measurements were used to study selenium influence on photosystem activity in rape seedlings affected by Cd stress. Water cultures containing Hoagland nutrients were supplemented with 400 microM of CdCl(2), 2 microM of Na(2)SeO(4) and a mixture of both CdCl(2) and Na(2)SeO(4). The seedlings were cultured till the first leaf reached about 1 cm in length. Cadmium-induced changes in the activity of both photosystems were partly diminished by Se presence in the nutrient medium. Electron microscopy photographs confirmed less degradation in chloroplasts of plants cultured on media containing Se. It is suggested that sucrose groups of starch, which is deposited in greater amounts in Cd-stressed plants, may act as traps for free radicals produced under those conditions.