Asexual propagation of stackhousia tryonii: A step towards restoration of a rare metallophyte

Stackhousia tryonii Bailey is a rare, serpentine-endemic herb, with potential for use in phytoremediation and /or phytomining. This study evaluates the use of herbaceous heel cuttings to propogate S. tryonii on three rooting media [sand, Medium 1; a commercial nursery mix, Medium 11; and sand: peat moss: perlite (2:2:1; v/v), Medium 111] following the application of plant growth hormones, viz. indole-3-butyric acid and naphthalene acetic acid (both as pure and commercial formulations, viz. Clonex Gel-green, Gel-purple and Gel-red), and honey. Cutting survival, rooting percentage, the number of primary and secondary roots produced, the length of the longest root and the total root length were evaluated after 10 weeks. Results show that there was a positive (P<0.001) influence of plant growth regulator treatments on cuttings' survival. Medium 111 failed to support survoval of cuttings. Percentage rooting (as a proportion of original number of cuttings was 10-30% higher in Medium 1 than in Medium 11. Cuttings treated with Clonex Gel-red, IBA at 1000ppm and NAA at 250 ppm had 60-70% higher percentage rooting in Medium 1 than in Medium 11. Total number of primary roots per rooted cuttings was significantly (P<0.05) higher in Medium 1 than in Medium 11. We conclude that cuttings from mature plants of S. tryonii could be effectively used to multiply S. tryonii, particularly with sand as rooting medium prior to treatment of cuttings with Clonex Gel-red.