Diesel Trees - Bioenergy Crop Plants - page 623

oleoresin. Terpenoids are the largest class of secondary metabolites produced in the plant kingdom.
Approximately 50,000 of these have been structurally identified (McCaskill and Croteau 1997).
This diverse group of plant metabolites is important for many aspects of plant biology and ecology
(Tholl 2006; Yuan et al. 2009). For instance, some terpenoids function in plant defenses against
herbivores and microbial pathogens (Gershenzon and Croteau 1991). Other terpenoids produced by
flowers as volatiles are involved in attracting insect pollinators for plant cross-pollination (Raguso
and Pichersky 1999). Some volatile terpenoids are emitted from herbivore-damaged plants and
function as cues to attract natural enemies of the feeding herbivores (Yuan et al. 2008). Copaifera
oleoresin is generally believed to be involved in plant defenses that can be mainly attributed to
terpenoids. Depending on the mechanisms of production, oleoresins may act in constitutive defense,
induced defense, or both. Copaifera oleoresin could be toxic to herbivorous insects, bacteria, or
fungi. Because of high volatility, the terpenoids in Copaifera oleoresin may be released from the
tree as infochemicals which can deter potential insect pests. Oleoresin may also flow out of the
wound to physically push the invading insects out of the entry wound or entomb them, so the
insects cannot cause further damage. The wound caused by insect herbivory can be a natural site
for invasion of microbial pathogens that would need to be defended against. Copaifera oleoresin and
its constituents have been documented to have antimicrobial and antifungal activity (Howard et al.
1988; Braga et al. 1998). Copaifera oleoresin produced upon insects feeding may therefore prevent
further damage caused by pathogens.
Studies on C. langsdorfii populations have showed that seedlings have a higher sesquiterpene
concentration than their parent trees (Macedo and Langenheim 1989b). Additionally, there was
a 48% mortality rate of first-generation oecophorid larvae and pupae when they were reared on
seedling leaves, but no mortality was seen on oecophorids reared on parent leaves. The oecophorids
that survived feeding on seedling leaves also exhibited a significantly lower weight gain than those
feeding on parent leaves. Seedlings had twice as much caryophyllene, the major sesquiterpene pres-
ent in most species' oleoresin, in leaves when compared with their parents. It is still unknown how
tapping Copaifera trees for oleoresin affects tree health in the long term. Initial tapping, or even
multiple tappings, could harm the tree by removing a source of chemical defense against pathogens
and insects and must be considered in future studies.
24.5 oleoresIn ProductIon ecoloGy
Extractive collection of the oleoresin from wild populations of Copaifera trees has long been touted
as a means to supplement income for native people in rural and forest areas instead of participating
in the destructive practices such as slash-and-burn agriculture and timbering. However, the viability
of this practice has been called into question because of the intermittent presence of oleoresin
amongst individual trees, low yields of oleoresin per tree, as well as reduced and questionable
secondary harvests of trees that produce oleoresins on the first tapping (Plowden 2003; Medeiros
and Vieira 2008). Sustainable production of quality oleoresin for medicine and other uses has many
problems that must be considered. First, a management system that will maximize production and
minimize impact on the forest where harvest is occurring must be described (Rigamonte-Azevedo
et al. 2004). This matter is complicated by the fact that the genus Copaifera is made up of many
species that can produce useful oleoresin, and each of these species will naturally respond differently
to each possible management strategy. In addition, anecdotal evidence suggested that each tree
could produce between 20 and 30 L of oleoresin from one drill hole every 6 months (Calvin 1980);
however, these stories seem to be more myth than fact.
In a study of 43 C. multijuga individuals in the Adolpho Ducke Forest Reserve in Manaus,
Brazil, about half produced some volume of oleoresin during three tappings (Medeiros and Vieira
2008). Six of these individuals never produced oleoresin at all. On average, trees with a diameter
at breast height (DBH) more than 41 cm produced 1.8 L of oleoresin per tree on the first tapping
and 0.5 L during the second tapping 1 year later. Trees of 30 and 41 cm DBH produced an average