Age-related changes in defensive traits of Acacia tortilis Hayne

GOWDA, J.H.; PALO, R.T.

AFRICAN JOURNAL OF ECOLOGY

Año: 2003 vol. 41 p. 218 - 223

0141-6707

The theory of plant defences proposes that investments in physical and chemical defences are driven by the risk of herbivore damage, and limited by the cost of producing the particular defensive trait in terms of resources that could be directed to other sinks, such as growth and reproduction. We sampled twigs of eighteen mature A. tortilis trees and their cohort of juveniles, to test some predictions of the above named theory. We expected a higher allocation of defensive traits to leaves and twigs in young plants than in mature ones due to a higher risk of damage by ungulates at the juvenile stage. Our results show that juvenile plants produce more spines along their twigs but have lower concentrations of phenolic compounds in their leaves than mature ones. We also expected a negative relation between concentration of foliar nutrients and phenolic compounds as predicted by the carbon/nutrient hypothesis. Only mature plants showed this pattern. Reproduction (in mature plants) and water stress (in juvenile plants) did not relate to allocation to secondary compounds as predicted by current hypotheses of plant defence