Nowadays, increasing significance is attributed to renewable energy sources, including the green energy provided by the short rotation energy woods as shrub willow (Salix spp.). The biomass productivity of willow plants depends both on the genetic potential of the given plant and the used cropping system. Farmers will cultivate this crop on marginal lands if similar profit can be generated as with cereal crops competing for the same land. In order to reach a wider use of energy willow, innovative agrotechnological solutions are needed to increase biomass productivity. Here we tested various protocols for using biostimulators as 1-triacontanol (TRIA), a saturated primary alcohol and seaweed extract (KELPAK) in Inger and Tordis energy willow cultivars. As first technology, stem cuttings were pre-soaked in TRIA 10 mg l-1 or in KELPAK 25% stimulator solutions.

These treatments significantly enhanced the length of woody stems in the Inger plants in comparison with the water-treated ones. Responses of Tordis plants were moderated to TRIA 10 mg l-1 treatment. The stem diameters of both Inger and Tordis plants were increased after the application of these stimulators. Root biomass of Inger plants was stimulated by treatment of cutting with KELPAK 25% solutions. In order to reduce the cost of stimulator application, we have tested combined technology based on soaking stem cuttings in TRIA (10 mg l-1) solution for 48 hours before planting and spraying outgrown plants with KELPAK 1% or KELPAK 2% solution. This protocol increased the photosynthetic activity, especially in Inger plants. Higher photosynthetic pigment

contents were detected in leaves of treated plants. By using a digital imaging-based phenotyping platform, we recorded improved growth rate and biomass yield in the root system. The presented experimental findings can support the introduction of novel cultivation systems for energy willow plantations.

Keywords: green energy, Salix, biomass, stimulator, photosynthesis, pigments