EFFECT OF CROP DENSITY AND NITROGEN AVAILABILITY ON BIOMASS AND RESIN FOR TWO Grindelia chiloensis (Asteraceae) CONTRASTING GENOTYPES

MONTASTRUC, M Y RAVETTA, D.A.

Chillan, Chile

Congreso; 21st Annual Meeting of the Association for the Advancement of Industrial Crops, Chillan, Chile, Nov. 20009; 2009

Association for the Advancement of Industrial crops

Grindelia chiloensis (Corn.) Cabr.  is a shrub native to arid environments in Argentina, being developed as a new resin crop.  Diterpene resin acids are deposited externally on leaves, stem and inflorescences have industrial applications in the production of paints, lacquers, varnishes and glues.  The plant’s genotype sets the limit for potential resin content although realized resin production is under strong environmental influence and has been found to conform to the Growth-Differentiation –Balance Hypothesis. The objective of this study was to assess physiological and morphological responses to changes in crop density and nitrogen availability in two G. chiloensis genotypes which differ in potential resin production.   We predict that the genotype with higher resin content will be associated with traits that reflect a more conservative resource use strategy. A field experiment was carried out in a completely randomized design with three factors: two levels of nitrogen availability, four densities (4.7, 6.7, 11.0 and 16.7 plants. m-2) and two genotypes of Grindelia chiloensis (accessions 743 and 775), with four replicates (plots) per treatment.  We report preliminary data after one and a half years of growth on aboveground biomass, specific leaf area (SLA), and leaf resin content.  Aboveground biomass was significantly affected by plant density. The highest individual plant-biomass was found at the lowest density and the lowest biomass at the highest density. Soil nitrogen content had no effect on individual biomass production.  Plot biomass production was significantly affected by plant density for both accessions. We found differences between genotypes in leaf resin concentration. Accession 775 had significantly higher leaf resin concentration than accession 743, while SLA was significantly lower for 775 than for 743. Resin content per unit leaf-area showed no significant differences between accessions.    We propose that these differences in SLA and resin concentration should be related to differences in resource use (sensu Grime 1979). The lower leaf resin concentration (g.g-2) together with the higher SLA in accession 743 would be associated with a greater potential for acquiring resources and higher biomass production, while accession 775 showed a more conservative strategy.  At the crop level these different strategies of resource acquisition and partition should produce two contrasting crops, one with  more stable resin content, adequate for lower resource environments (accession  775) and one with high resin production potential (at the whole plant level) but resource demanding (accession 743).