Stimulation of energy willow biomass with triacontanol and seaweed extract

Biomass productivity of shrub willow plants grown in short rotation system can be improved by genetic means or by innovative cropping technologies. In the present study we analyzed the growth and physiological responses of willow plants to plant biostimulators, such as 1-triacontanol (TRIA), a saturated primary alcohol and seaweed extract (Kelpak®). Testing a novel approach, we soaked stem cuttings in TRIA or Kelpak solutions for 48 h before plantation. These treatments enlarged height and diameter of stems, furthermore increased stem and leaf weights in comparison to the water control. In agreement with these greenhouse observations, field tests showed statistically significant enhancement in height and diameter of woody stems harvested in winter. Application of 25% Kelpak solution was the most effective in stimulating all traits including stem weight per plant after pre-planting treatment of cuttings. In an alternative treatment protocol, Kelpak was applied as foliar treatment or in combination between TRIA (10 mg L−1) treatment of cuttings and foliar spray with Kelpak 1 or 2% solutions in the greenhouse. The green pixel numbers revealed variable degrees of stimulation in shoot growth. These treatments resulted in an increase in stem and leaf weights. Improvement of photosynthetic functions was indicated by more efficient electron transport rates (ETRs) of photosystems. An increased nicotinamide and thiamine contents were detected in the leaves of stimulated plants. The present study can serve as a foundation for additional laboratory and field studies optimizing the application of these stimulators in energy plantations.