Scots pine as a model plant for studying the mechanisms of conifers adaptation to heavy metal action: 1. Effects of continuous zinc presence on morphometric and physiological characteristics of developing pine seedlings

Effects of zinc (50–150 μM ZnSO₄) on seed germinability, morphometric and physiological characteristics of Scots pine (Pinus sylvestris L.) seedlings during first 6 weeks of their development were studied. Scots pine turned out to be rather sensitive to elevated zinc concentrations. This was manifested in reduced seed germinability, root system growth retardation and suppression of its development (primarily, reduction in the size of the zone of secondary root formation, their number, and total length), a disturbance in the dynamics of biomass accumulation by various organs, primarily true needles, and also the content of main photosynthetic pigments. A specificity of zinc accumulation in seedling organs was established; it depended on the degree of root system development. A competition between cotyledons and needles for essential elements was observed. It was concluded that Scots pine high sensitivity to relatively low zinc concentrations (50–150 μM) makes it a more convenient model than currently used model plants (Arabidopsis thaliana L., Mesembryanthemum crystallinum L., Brassica napus L., and others) for studying physiological and molecular mechanisms of conifers adaptation to heavy metals and also for predictions of possible ecological consequences of environment pollution with zinc for tree phytocenoses.