The legalization of Cannabis sativa L. for recreational and medical purposes has been gaining global momentum, leading to a rise in interest in Cannabis tissue culture as growers look for large-scale solutions to germplasm storage and clean plant propagation. Mother plants used in commercial propagation are susceptible to insect pests and disease and require considerable space. While micropropagation can produce disease free starting material in less space, current published in vitro micropropagation methods are not robust and few report high multiplication rates. Further, these micropropagation methods rely on photoperiod-sensitive plants which can be maintained in a perpetual vegetative state. Current methods are not adaptable to long-term tissue culture of day-neutral cultivars, which cannot be maintained in perpetual vegetative growth. In this study, we chose to develop a micropropagation system which uses C. sativa inflorescences as starting materials. This study used two cannabis cultivars, two plant growth regulators (PGR; 6-benzylaminopurine and meta-topolin) at different concentrations, and two different numbers of florets. Here we show that floral reversion occurs from meristematic tissue in C. sativa florets and that it can be used to enhance multiplication rates compared to existing in vitro methods. Floret number was shown to have a significant impact on percent reversion, with pairs of florets reverting more frequently and producing healthier explants than single florets, while cultivar and PGR had no significant effect on percent reversion. Compared with our previously published nodal culture studies, the current floral reversion method produced up to eight times more explants per tissue culture cycle. Floral reversion provides a foundation for effective inflorescence-based micropropagation systems in C. sativa.

The legalization of Cannabis sativa L. for recreational and medical purposes has been gaining global momentum, leading to a rise in interest in Cannabis tissue culture as growers look for large-scale solutions to germplasm storage and clean plant propagation. Mother plants used in commercial propagation are susceptible to insect pests and disease and require considerable space. While micropropagation can produce disease free starting material in less space, current published in vitro micropropagation methods are not robust and few report high multiplication rates. Further, these micropropagation methods rely on photoperiod-sensitive plants which can be maintained in a perpetual vegetative state. Current methods are not adaptable to long-term tissue culture of day-neutral cultivars, which cannot be maintained in perpetual vegetative growth. In this study, we chose to develop a micropropagation system which uses C. sativa inflorescences as starting materials. This study used two cannabis cultivars, two plant growth regulators (PGR; 6-benzylaminopurine and meta-topolin) at different concentrations, and two different numbers of florets. Here we show that floral reversion occurs from meristematic tissue in C. sativa florets and that it can be used to enhance multiplication rates compared to existing in vitro methods. Floret number was shown to have a significant impact on percent reversion, with pairs of florets reverting more frequently and producing healthier explants than single florets, while cultivar and PGR had no significant effect on percent reversion. Compared with our previously published nodal culture studies, the current floral reversion method produced up to eight times more explants per tissue culture cycle. Floral reversion provides a foundation for effective inflorescence-based micropropagation systems in C. sativa.

To investigate the effect of palm leaf biochar on the element absorption and reduction of drought stress effects in melon plants, an experiment was conducted using a split plot in a randomized complete block design with three replications in two successive years. The main plot contained three levels of drought stress (60%, 85%, and 100% water requirement) and the subplot contained four levels of biochar (0, 150, 300, and 450 g per plant). The results revealed that biochar application reduced the effect of drought stress and thus proline content in plants. Application of 300 g biochar per plant with 100% water requirement increased total chlorophyll by 131% compared to control. The treatment of 450 g biochar per plant with 100% water requirement increased chlorophyll a and b and leaf nitrogen (N), potassium (K), calcium (Ca), and manganese (Mn) content by 169%, 127%, 58%, 65%, 44%, and 48%, respectively, compared to control. The treatment of 450 g biochar per plant increased phosphorus (P) and magnesium (Mg) content of leaves by 20% and 31%, respectively, in comparison with control. The interaction of drought stress and biochar indicated that the treatment of 450 g biochar per plant with 60% of water requirement increased plant iron, zinc, and copper by 60%, 44%, and 66%, respectively, compared to the biochar-free treatment with 100% water requirement. Addition of 450 g biochar per plant and irrigation with 60% of water requirement increased soil N, P, and K by 150%, 13%, and 75%, respectively, compared to the biochar-free treatment with 100% water requirement. The results indicated that the use of biochar can be a successful strategy for improving water use efficiency and reducing drought stress in melon plants.

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