Propagation of yellow bells (Geleznowia verrucosa Turcz., Rutaceae) from seed

Abstract

Geleznowia verrucosa Turcz. (Rutaceae) is a commercially important, bush-picked wildflower that has no known commercial means of propagation. This study examined factors influencing seed dormancy and likely to restrict germination of the species. Germination of entire, untreated seed was low (less than 2%), but removal of a small portion of the testa at or near the radicle end of the seed improved germination. This response was affected by the temperature under which the seed germinated, but was unaffected by exposure of the seed to light while germinating. The percentage germination of nicked seeds 52 days after sowing increased from 8% to 16-19% by increasing the temperature from 15/10¦C to 20/15¦C; 55-60% of nicked seed germinated when the germination temperature was increased to 23/15¦C. The germination of nicked seed was reduced by leaching in running tap water. Following 1 week of leaching the germination percentage of nicked seed at day 52 in the glasshouse was reduced from 16% to 9%, with a further decrease to 5% after 2 weeks of leaching. There was also no stimulatory effect on the germination of entire seeds by stratifying the seed at 5¦C after periods of solarisation. It is concluded that dormancy of fresh seeds of G. verrucosa is caused, in part, by the mechanical restriction of the testa on embryo growth and elongation.