Pre-germinative requirements of Maihuenia patagonica and Maihueniopsis darwinii, endemic cacti from Patagonia

Abstract

Cacti are characteristic plants in arid ecosystems, where they play an important ecological role. Many species are threatened because of habitat destruction and collection for commercial purposes. In South America, Argentina is one of the countries with the greatest cacti richness and endemisms. However, cacti have been scarcely studied, especially the southernmost species. Since the study of cacti’s reproductive biology would help to improve their conservation status, we studied basic physiological aspects of the germination of two endemic species of Argentina and Chile, Maihuenia patagonica (Phil.) Britton & Rose and Maihueniopsis darwinii (Hensl.) F. Ritter var. hickenii (Britton & Rose) R. Kiesling. Germination percentage (G), mean germination time (TMG) and time until germination (IG) of control seeds and seeds subjected to three pre-germinative treatments were evaluated. Treatments were cold moist stratification for 40 days, mechanical scarification with sand and sandpaper, and mechanical scarification with a scalpel. Laboratory assays were performed at 20/10 °C and 12 h light/12 h dark regime during 60 days. In M. patagonica germination in the stratification treatment did not differ from the control, but was higher in the scarification with scalpel. In M. darwinii var. hickenii germination only differed between the stratification and the scarification with scalpel. TMG and IG were higher in the stratification treatment than in the control for M. patagonica, whereas scarification treatments did not differ from the control. As for M. darwinii var. hickenii no differences were detected for TMG, but the IG was lower in the stratification than in the control. Probably both species presents some kind of dormancy, since germination percentages were low (M. patagonica between 8-27 % and M. darwinii var. hickenii between 17-26 %) but seeds presented high viability. Presence of physical dormancy is discarded because control seeds of both species germinated and the presence of non deep physiological dormancy is proposed. The latter was partially overcome by mechanical scarification in M. patagonica. These results are a new contribution to the study of cacti in South America and could help to develop in situ conservation strategies through the restoration of degraded areas.