The southern South American Proteaceae, Embothrium coccineum exhibits intraspecific variation in growth and cluster-root formation depending on climatic and edaphic origins

Abstract

Background and aims: Cluster root (CR) functioning has been studied mainly in Proteaceae species from (P)-deficient old soils. However, in southern South America, six species occur in young P rich soils. The aims were: i) to study the growth and CR formation of Embothrium coccineum seedlings from populations contrasting in edaphic and climatic conditions and, ii) to study the effect of P availability on CR formation. Methods: Seedlings were grown from seeds collected from nine Chilean populations of E. coccineum (36° to 45° S). After 9 months in a nursery, CR formation and growth were determined. Additionally, seedlings from the two populations at the extreme ends of the distribution were maintained on sand and watered with nutrient solutions including or excluding P. Results: All seedlings showed CR formation at 4 months old; however, CR allocation differed in that it was lower in plants from the north versus from the south. CR in seedlings from Curacautín (38°) were suppressed when P supply increased, though this was not seen in seedlings from Coyhaique (45°). Conclusions: Results suggest local root adaptation related to both climatic and edaphic conditions. We hypothesize that these features could favor Proteaceae persistence in southern South American ecosystems.