In this study it was observed that the photosynthesis process was considerably improved in plants developed in the presence of all natural products, investigated after the plants have been in the soil for 30 and 60 days.
Analyzing the variation of assimilation rate for the sunflower plants in the presence of the tested solutions it was noticed that the highest intensity was identified in the plants developed in the presence of spruce bark extract (SB1 with 58.43% and SB2 with 54.25% higher than the assimilation rate registered for the control) and of deuterium depleted water (DDW- with 42% higher than the assimilation rate determined for the control). At the same time, for this variants the increases of transpiration rate and sub-stomatal cavity CO2 concentration were noted (Table 2).