Manipulating dormancy of capeweed (Arctotheca calendulaL.) seed

Abstract

Capeweed (Arctotheca calendula) seeds were found to be dormant at harvest. Effects of duration and temperature of storage under ‘laboratory’ and ‘natural’ conditions, growth regulators, stratification and age of seeds, were studied on the germination of dormant seeds. Three factors imposed on seeds were found to promote germination of capeweed: (i) allowing seed to age, either in storage, buried in soil or during stratification (germination of 18-month-old seeds was up to 60% higher than that of fresh seeds); (ii) the presence of light (the average germination percentage of seeds exposed to light during storage was 3.2-fold greater than that of seed stored in the dark); and (iii) the application of growth regulators, particularly gibberellic acid, enhanced by scarification (GA3 and ethephon promoted germination by up to 58% when applied to scarified seeds). Other factors, e.g. temperature and depth of storage, influenced germination but were less critical to its success. These results provide a preliminary assessment of the importance of these factors in controlling dormancy in seeds of capeweed.