Productivity and Quality Evaluation of Tarragon and Thyme Grown Under Artificial Light

Abstract

The research aimed at evaluation of productivity and quality of tarragon and thyme medicinal material was carried out on hydroponic installations during 2019-2020. The objects under study were Monarkh and Gudvin tarragon varieties as well as Medok and Zmeyka thyme varieties. The plants were grown in mineral cotton substratum. Fertikea Hydro complex fertiliser with microelements and calcium nitrate were used. The growing conditions: ambient temperature +22…+25℃, solution temperature +20℃, ambient humidity 55…65%. Experiment regimens: growing under white LEDs (luminous flux 8000 lm, color temperature 4000 K, PPF 165 mkmol/s/m2) and color LEDs (combination of red, blue and white LEDs (32:16:32), luminous flux 6573 lm, PPF 143 mkmol/s/m2), for 16-hour light regimen. We found that thyme grown on a vertical hydroponic system increase its biomass 2.0…3.5 times compared to the conventional growing. The highest productivity of Zmeyka thyme variety is reached under white light, while for both the tarragon varieties and Medok thyme variety it is reached under coloured LEDs. Chlorophyll-a content in green biomass is a little higher under coloured LEDs for Zmeyka thyme variety and Gudvin tarragon variety, while the reverse trend is observed for Monarkh tarragon variety. All the varieties show higher chlorophyll-b content under coloured LEDs. Combined chlorophyll-a and chlorophyll-b content increases under coloured LEDs for the thyme varieties and Gudvin tarragon variety. Monarkh tarragon variety shows the highest combined chlorophyll content under white LEDs. Carotenoid concentration in Medok thyme variety and Monarkh tarragon variety is higher under white LEDs and it is higher under color LEDs for the rest of the varieties. Flavonoids in the studied varieties accumulate statistically better (1.5…3.0 times) under white LEDs