Overcoming dormancy and enhancing germination of seven Malvaceae species adapted to semi-arid regions

Abstract

Seven Argentinian native species of Malvaceae with ornamental value are potential candidates for revegetation programs of semi-arid regions. We examined the seed imbibition, germination and type of dormancy in Sphaeralcea australis, S. crispa, S. mendocina, S. bonariensis, Lecanophora heterophylla, Modiolastrum australe and Rhyncosida physocalyx. Mechanical and chemical scarification, gibberellic acid and combined treatments were used to break dormancy. The results show variability in the degree of water imbibition and also in the type of dormancy. S. crispa seeds have negligible or non-dormancy, but the seeds of S. australis, S. mendocina, S. bonariensis, Lecanophora heterophylla, Modiolastrum australe and Rhyncosida physocalyx present different degrees of physical dormancy imposed by the hard seed coat. Also, they present some degree of physiological dormancy. Mechanical scarification was the most efficient treatment to overcome latency. Germination percentages after mechanical scarification treatments were greater than 50% for S. bonariensis, Lecanophora heterophylla and Modiolastrum australe, greater than 75% for S. australis, S. mendocina and Rhyncosida physocalyx, and almost 100% for S. crispa. This work is a contribution to the conservation of seven native species of Argentinian Malvaceae, with the potential to be used as ornamental plants in sustainable landscaping and in rehabilitation and restoration programs of semi-arid environment.