Vegetative growth and alkaloid concentration of Sceletium Tortuosum (L.) N.E. Br. in response to different soilless growing media and fertigation regimes in hydroponics

Abstract

The purpose for this study was to investigate whether Sceletium tortuosum was suitable for cultivation in hydroponics and to determine whether different soilless media and fertigation regimes would have an effect on the vegetative growth and alkaloid concentration of the plant. The experiment was conducted over a period of 6 weeks. Three hundred plants were cultivated from one initial mother plant obtained from Verve Dynamics (Pty) Ltd, Somerset West. Twenty treatments were evaluated with 15 sample replicates. Treatments were made up of 4 different soilless growing media, namely: pure silica sand (SS), 50% silica sand with 50% coco-peat (SC), 50% silica sand with 50% vermiculite (SV), and 50% silica sand with 50% perlite (SP). These growing media were tested in conjunction with 5 different fertigation regimes (FR), plants treated with fertigation regime 1 (FR1) received aqueous nutrient solution once every week, fertigation regime 2 (FR2) received aqueous nutrient solution once every second week, fertigation regime 3 (FR3) received aqueous nutrient solution once every third week, fertigation regime 4 (FR4) received aqueous nutrient solution once every fourth week and fertigation regime 5 (FR5) received aqueous nutrient solution once every fifth week respectively. Chapter 2 reviewed the importance of S. tortuosum and its viability as a Traditional African Medicinal Plant. It was found that S. tortuosum has clear pharmaceutical and economical importance and is one of the only known plants to contain the alkaloids mesembrenone and mesembrine which can be utilized for the promotion of health and treating a variety of psychological disorders such as anxiety and depression. In chapter 3 it was seen that the various treatments had significant effects in terms of plant root growth, shoot growth and dry weight. Treatment SCFR3 showed the highest individual mean value for root growth, while the average from treatments SVFR1-5 displayed the highest average value. The lowest individual value for root growth was observed in treatment SPFR5. Overall treatments with fertigation regime FR3 had better root growth, while fertigation regimes FR5 showed sub-optimal root growth. For shoot growth the highest individual mean value was found in treatment SVFR1, while the highest average value was observed in treatments SCFR1-5. In chapter 4 treatments also had a significant effect on alkaloid concentrations. It was observed that shoot extracts contained a higher concentration of total alkaloids than root extracts, however root extracts had an overall higher amount of delta 7 mesembrenone, and mesembrenone in terms of area %, while shoots had higher amounts of mesembrine. Further the mesembrine standard as mentioned in 4.4.5, shoots clearly have an overall higher concentration of mesembrine than roots. These results suggest that roots of S. tortuosum should be harvested for the purpose of extracting delta 7 mesembrenone and mesembrenone molecules, while the shoots should be harvested for extracting mesembrine. Chapter 5 further investigated the interaction between the vegetative growth and alkaloid concentration of S. tortuosum. There appears to be a clear trend that displays higher concentrations of mesembrine where shoot growth was more optimal, however more optimal growth did not display a higher concentration of total alkaloids. In terms of root growth and total alkaloid concentration, it did not appear that more optimal growth induced higher concentrations of total root alkaloids, meaning reasonable stress on plant root and shoot growth could possibly promote higher concentrations of total alkaloids. It is also clear that overall roots contain more delta 7 mesembrenone and mesembrenone than shoots, suggesting roots should be harvest for extracting these molecules specifically. In most cases high results of delta 7 mesembrenone in roots also had similar amounts of mesembrenone, however certain treatments resulted in higher concentrations of the former and the latter, therefore their similar molecular structure does not always permit similar manifestation in the plant material. Overall this study has found that S. tortuosum is suitable for cultivation in hydroponics, and that soilless media, fertigation regimes as well as soilless media in conjunction with fertigation regimes affected the vegetative growth and alkaloid concentration of S. tortuosum. This research has shown that some soilless media and fertigation regime treatments had more desirable results in terms of vegetative growth and/or alkaloid concentration of the plant.