Density and substrate effects on morphological and physiological parameters of plant stock material of four forest species grown in mini-plugs

Abstract

The aim of this study was to measure a number of morphological and physiological parameters of planting stock material of forest species grown in mini-plugs and to evaluate them as indicators of planting stock quality under different density and substrate treatments. The studied species were black locust (Robinia pseudoacacia L.), Italian cypress (Cupressus sempervirens L.), brutia (Pinus brutia Ten.) and black pine (Pinus nigra Arnold). Seeds were sown in two growing substrates (peat and stabilized medium), using two mini-plug densities (3500 and 975 mini-plugs m−2). After a 4–5 week growth period under controlled conditions, both morphological (root length, shoot height, leaf area, root and shoot dry weight) and physiological (shoot electrolyte leakage, root growth potential) parameters were assessed. The use of stabilized growing medium and lower densities resulted in higher quality seedlings of black locust, black and brutia pine, in terms of growth and physiological status. In the case of Italian cypress, the use of low density improved seedling morphological characters, but negatively affected its root growth potential. Moreover, this species performed better when peat was used. Correlation analysis showed that for brutia and black pine, seedling morphological traits reliably reflect seedling quality during the precultivation phase in mini-plugs.