The effect of scarification, temperature and light conditions on seed germination of Artemisia afra jacq. Ex willd.

Abstract

Artemisia afra Jacq. ex Willd is a common medicinal plant in Africa belonging to the Asteraceae plant family. It has been used for decades as a treatment for cold related illnesses and a variety of other ailments such as asthma, malaria and kidney disorders. As such this has led to its high demand and it is faced with threats of overharvesting. As the plant is naturally occurring and not widely cultivated, it’s seed biology and germination properties are not documented. The optimum requirements (temperature and photoperiod) for seed germination as well as the effects of Moringa based biostimulant and different scarification methods were investigated on A. afra seeds in this study. The seeds were exposed to different scarification methods including physical scarification (rubbing using sandpaper), hot water soaking, cold water soaking, acid treatment (H2SO4) and fermentation (using effective microorganisms) while the untreated seeds served as the control under all conditions. Moringa based biostimulant was also used as a seed priming agent at 0, 0.5, 1 and 3% levels. The seeds were then placed under a variety of photoperiods including constant light, alternating light (16/8 hours) and continuous darkness at different temperatures (15°C, 25°C and 35°C). Germination percentages and mean germination time (MGT) were calculated from the results and Statistix 10.0 software was used at the probability level of 5%, to compare the mean values. It was observed that under the different temperatures without any other treatments, the highest germination rate (70%) was achieved at a 25°C. No germination (0%) was obtained at both 15°C and 35°C in all the experiments including scarification methods and photoperiods. Under the scarification treatments, soaking in hot and cold water scarification improved germination with final germination of 70%, compared to the other scarification methods (Physical at 20%, acid treatment at 20% and control at 10%). There was no germination observed (0%) for the fermented seeds in all the experiments. On the photoperiod treatments, the highest germination percentage of 70% was observed under alternating light condition. However, when mean germination time was calculated, continuous xiv darkness resulted in shortest MGT of 11 days compared to 13 days for both alternating light and for continuous light in this set of experiment. Seed priming with Moringa based biostimulant under alternating light conditions and at 25°C resulted in improved MGT. Under the investigated treatments, the use of 3% biostimulant exerted the highest improvement on germination with germination percentage of 62% and the shortest MGT of 7 days compared to the other treatments. Generally the final germination (%) and time of A. afra seeds were affected by scarification, temperature, light and priming using Moringa based biostimulant. The information generated from this study is important because it will contribute in bridging the scientific gap on the information that has never been documented on optimum requirements for effective propagation of A. afra through seeds. As such this information will be useful for small scale farmers and medicinal plant growers who are willing to recover the lost populations of A. afra through seed propagation thus improving their supply and income