Planta Med 2011; 77 - P_7
DOI: 10.1055/s-0031-1273536

Variations in Photosynthesis, Transpiration, Water Use and Cannabinoid Contents in Field Grown Drug Type Varieties of Cannabis sativa L.

S Chandra 1, H Lata 1, Z Mehmadic 1, IA Khan 1, 2, 3, MA ElSohly 1, 4
  • 1National Center for Natural Product Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, MS 38677, USA
  • 2Department of Pharmacognosy, School of Pharmacy, University of Mississippi, MS 38677, USA
  • 3Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
  • 4Department of Pharmaceutics, School of Pharmacy, University of Mississippi, University, MS 38677, USA

High potency Cannabis sativa plants propagated through vegetative cuttings were planted in the field for outdoor cultivation. These plants were monitored for their photosynthetic characteristics and cannabinoid contents during vegetative, flowering, budding and senescence stages. Different physiological parameters i.e. photosynthesis (P N ), dark respiration (R D ), transpiration (T R ), stomatal conductance (gCO2 ) and intercellular CO 2 concentration (C i ) were measured in these plants using Li-COR 6200 photosynthetic system. Mesophyll efficiency (C i /g S ) and water use efficiency (WUE, P N /T R ) were calculated based on P N , T R, C i and g S values. Cannabinoid contents (Δ9-THC, THCV, CBD, CBC, CBG and CBN) were measured simultaneously in these plants using gas chromatography-flame ionization detection (GC-FID). In general, an increase in the rate of P N was observed in this species with plant growth from vegetative to early budding stage followed by a decrease during later growth stages. A reduction in WUE observed during the hot summer months is attributed towards its higher rate of T R . Diurnal and seasonal changes in the environmental conditions reveal that the effect of light intensity was found to be more prominent in regulating P N , whereas, the effect of temperature was more prominent in regulating T R in this species. Similar to P N , Δ9-THC content increased with plants age up to a highest level during budding stage where it reached a plateau for about a week before the plants were harvested. The changes in the concentration of other cannabinoids followed a similar pattern in some cases but show more variability depending on the variety. This study reveals a positive correlation between the rate of P N and Δ9-THC content in Cannabis sativa L. However, the level of significance varied with plant variety.

Acknowledgement: This work was supported in part by the National Institute on Drug Abuse (NIDA), National Institute of Health (NIH), Department of Health and Human Services, USA, Contract No. N01DA-10–7773.