Advertisement

STRUCTURE, ENVIRONMENTAL EFFECTS ON THEIR FORMATION, AND FUNCTION OF PROTEOID ROOTS IN LEUCADENDRON LAUREOLUM (PROTEACEAE)

Authors


Summary

Proteoid roots are abundant on field and potted plants of Leucadendron laureolum (Lam.) Fourcade, accounting for up to 40% of the root mass (in 9-month-old plants in sand), and up to 400 g−1 of new season's roots (in 18-month-old plants in humus-amended sand). There may be over 250 hairy rootlets per 10 mm of parent axis, giving a total surface area almost 15 times that of an equivalent mass of parent roots. Microsymbionts are absent, but chlorornycetin suppressed proteoid root formation, providing limited evidence of the need for a bacterial cofactor. Proteoid roots formed preferentially in humus-amended sand but were elminated, with little effect on non-proteoid roots, when organic fertilizer high in P was added. In the field, proteoid roots were confined to a 50 mm wide root mat just beneath the leaf litter around the parent plant. The greater soil volume explored directly by proteoid roots, despite lower soil P availability, may largely explain the greater rate of P uptake by plants in Clovelly sand than that m Hutton clay-loam, although differential rates of solubilization and root respiration also appeared to be involved.

Ancillary