Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome

Phosphorus (P) is an essential macronutrient required for many central metabolic processes, and is therefore a major factor governing plant development, structure and function. Cannabis is a short-day plant that its' development progression involves a vegetative growth phase under long photoperiod, followed by a reproductive phase under a short photoperiod. The reproductive inflorescence yield potential in cannabis is therefore largely dependent on the morphology and physiological condition of the plants at the vegetative phase. Due to legal restrictions, there is lack of science-based knowledge about cannabis plant science, including mineral nutrition. The present study therefore focused on P nutrition of plants at the vegetative growth phase under long photoperiod. The plants were cultivated in pots in a controlled environment and subjected to 5 levels of P (5, 15, 30, 60, 90 mg L-1). We investigated impact on the ionome, physiological and morphological traits, uptake of nutrients into the plant, translocation to the shoot, and distribution in the plant organs for 2 medicinal cannabis genotypes. Plant biomass production, photosynthesis rate, stomatal conductance, transpiration rate and intercellular CO2 at the vegetative growth phase exceled under 30 mg L-1 P supply. Uptake and translocation of nutrients from root to the shoot was highly influenced by the P treatment. Under excess P supply, most of the plant P accumulated in the mots, and translocation to the shoot was inhibited. Uptake of Mg into the plants, and its' translocation to the shoot was inhibited by P deficiency in both cultivars, and was enhanced by increased P supply. Calcium uptake was increased by P application but translocation to the shoot was inhibited. Zinc retention in mots under P deficiency was found in both varieties. Our results suggest a wide optimum range for P in medicinal cannabis at the vegetative growth stage, with a minimum requirement of 15 mg L-1 P and a recommended application of 30 mg L-1. The functional physiology and ionome profiling revealed genotypic variability in P sensitivity.

Automated summary

Phosphorus plays a crucial role in the vegetative growth phase of medicinal cannabis, with optimal levels enhancing plant physiological traits such as biomass production, photosynthesis rate, and translocation of nutrients. Excess or deficient phosphorus can impact mineral nutrient uptake and translocation in cannabis plants.