Abstract
A. araucana is an endemic species of the temperate forests from Chile and Argentina; protected in both countries and categorized as in danger of extinction. Individuals of this species have begun to show foliar damage (i.e., discoloration) in branches and upper parts. The discoloration begins from the base to the top and from the trunk to the branches with necrotic rings appearing; in some cases causing death; and is currently attributed to an as yet unknown disease. This study focuses on the first protective layer of plants against environmental stress and pathogens; known as leaf waxes. The abundance and distribution of three classes of leaf waxes (long chain fatty acids; alkanes and alcohols) were measured in healthy individuals of A. araucana from different sites and individuals that present foliar damage (sick individuals). In the case of sick individuals; their leaf waxes were measured considering the level of leaf damage; that is; leaves without; medium and full foliar damage. The most abundant class of leaf wax in both sick and healthy individuals was fatty acids; followed by alkanes and then alcohols; with common dominant chains; C28 fatty acid; C29 alkane and C24 alcohol. Sick individuals have higher abundances of alkanes and alcohols than healthy individuals. The leaves of sick individuals have lower values of distribution indices (the carbon preference index of fatty acids and average chain length of alkanes) as foliar damage increases that are interpreted as a reduction of in vivo biosynthesis of waxes. This is the first evidence of A. araucana response to a still unknown disease that is killing individuals of this endemic species.
Highlights
The Araucaria araucana forest is found in the temperate forests of South America [1], where species like A. araucana and Nothofagus dominate, forming mixed stands with a dense understory dominated by Chusquea bamboos [2]
Fatty acids were greatest in abundance (from 445.8 ± 308.3 to 548.4 ± 82.6 μg/g alcohols (Figure 4, Supplementary Materials Table of dry leaf), followed by alkanes and alcohols
This study reports a high abundance of long chain fatty acids compared to alkanes and alcohols in leaf waxes of A. araucana
Summary
The Araucaria araucana forest is found in the temperate forests of South America [1], where species like A. araucana and Nothofagus dominate, forming mixed stands with a dense understory dominated by Chusquea bamboos [2]. The temperate forests have high endemism, and over time, the natural distribution of A. araucana forest has been reduced despite significant interest in conservation. A. araucana forests are distributed between the Chilean and Argentinian slopes of the Andean. The above are among the reasons why A. araucana is considered of high conservation value and protected on both sides of the Andean Mountains [10]. It has been declared a natural monument since 1990 in
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