Effects of zinc on Scots pine (Pinus sylvestris L.) seedlings grown in hydroculture.

The 6-week-old seedlings of Scots pine (Pinus sylvestris L.) showed high sensitivity to chronic exposure to zinc in hydroculture, which manifested in a significant inhibition of growth. Changes in the architecture of the root system and the suppression of its growth were shown to be the most striking effects of the toxic effect of zinc. Based on the data relating to the accumulation of zinc predominantly in the root system (by up to 35 times at 300 μM ZnSO4) and to the reduction in its translocation into the aerial organs, we concluded that P. sylvestris is related to a group of plants that exclude zinc. The seedlings developed a manganese deficiency (revealed by a reduction in Mn content in the roots and needles of up to 3.5 times at 300 μM ZnSO4) but not an iron deficiency (revealed by an increase in iron content of up to 23.7% in the roots and up to 42.3% in the needles at average). The absence of signs of oxidative stress under the effect of the zinc was detected as evidenced by the reduction in the content of malondialdehyde and 4-hydroxyalkenals in the seedling organs. The leading role of low molecular weight antioxidants in the prevention of oxidative stress in the seedling organs was suggested. Under the influence of zinc, a significant increase in the Trolox Equivalent Antioxidant Capacity of ethanol extracts of the seedling organs was found, which was caused by an increase in the total content of (+)-catechin and proanthocyanidins.
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