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Grindelia chiloensis (Asteraceae) is a shrub native to the Patagonia and Monte regions of Argentina and is presently under study as a resin crop. The production rate of diterpene resin acids is, partly, determined by environmental conditions and can be controlled by changing water and radiation availability or temperature. Although theory predicts that resin content should increase with low nitrogen availability, the responses reported in the literature are few, mainly in conifers and are not always consistent with predictions by the carbon nutrient balance hypothesis (CNBH).

The objective of this work was to test whether resin production is linked to nitrogen availability as predicted by the CNBH. Plants of G. chiloensis were grown in a greenhouse under four nitrogen availability conditions (0, 1.5, 3.0, and 6.0 mM of N) generated using a modified Hoagland solution. Structural and functional characters were measured. Leaf resin and root total non-structural carbohydrate content (TNC) were higher in plants grown with low nitrogen availability, whereas assimilation rate was slightly affected, in accordance with predictions. Under low nitrogen availability, shoot biomass, and leaf-stem ratio were lower. Resin composition was only slightly affected by nitrogen availability, suggesting that this character is under strong genetic control. (c) 2006 Elsevier B.V. All rights reserved.