Effects of water availability on growth, dry matter allocation and resin in seedlings of Larrea divaricata

CELLA PIZARRO, L.; BISIGATO, A.J.; RAVETTA, D.

Termás de Chillán, Chile

Congreso; XXI AAIC Annual Meeting; 2009

AAIC

Although usually more expensive than their synthetic equivalents, there is still interest in natural antioxidants considered best suited for human consumption. One potent antioxidant is nordihydroguaiaretic acid (NDGA) commercially extracted in the past from the North American Larrea tridentata, that has triggered a renewed effort to develop a source of NDGA from South American species of the genus Larrea. One of the reasons for this interest is the widespread distribution of L. divaricata and L. nitida throughout about one-fourth of Argentina’s continental territory.The aim of this preliminary study was to establish if moisture availability could differentially affect total biomass, its partition, and the production of phenolic compounds (external phenolic resins as well as total phenols) in seedlings of L. divaricata.A greenhouse experiment was carried out in which one-month old seedlings growing in 2,25 litres pots were subjected to five soil moisture contents as a percentage of dry weight: 13%, 11%, 9%, 7% or 5% (field water capacity for this soil is 15%). After 150 days, seedlings were harvested and oven-dried at 45º C for 48 hours. Each seedling was divided into roots, stems and leaves. Since resins are moderately lipophilic, they were extracted with ethanol by soaking the green leaves of each plant for one hour, filtering the extracts and evaporating until dryness.Total biomass, its partition and the production of phenolic resin and total phenols were not affected by water availability. On average, leaf dry-weight was 0.71 ± 0,03 g per seedling and their resin content was 20.9 ± 1,0 %. These results show that seedlings of L. divaricata have low sensitivity to water availability at least for the range of water supplied in this study. Resin content was high although the content of NDGA from this fraction has not been evaluated yet.This preliminary evaluation of biomass and resin content shows L. divaricata as a good candidate for continuing research towards developing a local source of antioxidants. A stable production of resin, independent of water availability, is considered a promising character towards the use of natural stands of L. divaricata from Patagonia and Monte regions in Argentina.