engleski

Effect of prolonged photoperiod on driving forces for photosynthesis in cannabis

Cannabis sativa L. subsp. sativa, or industrial hemp, has been cultivated for centuries for its nutritional and medicinal benefits. Recently, it has been introduced as functional food with indefinite health benefits and bioactive properties. Indoor cultivation implies control of plant life cycle, the optimum light quality, quantity and photoperiod which leads to a dynamic growth of Cannabis biomass as well as the production of desirable cannabinoid profile. Cannabis is a primary short–day plant and manipulations in photoperiod can favor vegetative growth or flower initiation. The aim of this study was to determine the influence of different photoperiods (16/8, 20/4 and 24/0 ; 250umol m-2s-1) on the photosynthetic efficiency in two cultivars of Cannabis (Finola and USO) by measuring fast chlorophyll a fluorescence. Both cultivars revealed lowest total performance index (PItotal) at 20/4 compared to 16/8 suggesting this was the least favorable light/dark ratio. By calculating total driving forces for photosynthesis (DFtotal), significant negative values were observed at 20/4 in both cultivars. Estimation of partial driving forces revealed that reductions in DFtotal were the result of more negative rate constants for electron transport between two photosystems (yE0) as well as of the events that involve PSI (dR0). Such results suggested that exposure to 20/4 photoperiod decreased the contribution of dark reactions to the overall potential of energy conversion in both Cannabis cultivars.

Industrial hemp ; photoperiod ; performance index ; photosynthetic electro potential

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