In general, the uptake of toxic metals may produce oxygen free
radicals and oxidative stress in plants. Loss of photosynthetic
pigments results in reduction of the efficiency of photosynthesis
and has the subsequent impact on the vitality of plants. In the case
of cultivation in the presence of uranium, there was a reduction in
chlorophyll a and b. Most notably, this effect was observed for the
tobacco plants cultivated using uranium hydroponic solution with
phosphates, which were sprayed by polyamines putrescine (Fig. 6).
Also carotenoid content decreased. In plants, polyamines play a
significant role in protection against abiotic stress; therefore the
decrease of photosynthetic pigment content in uranium stressed
plants after putrescine spraying is unusual. Sabbagh (2006)