What Do Microbes Encounter at the Plant Surface? Chemical Composition of Pea Leaf Cuticular Waxes

Abstract

In the cuticular wax mixtures from leaves of pea (Pisum sativum) cv Avanta, cv Lincoln, and cv Maiperle, more than 70 individual compounds were identified. The adaxial wax was characterized by very high amounts of primary alcohols (71%), while the abaxial wax consisted mainly of alkanes (73%). An aqueous adhesive of gum arabic was employed to selectively sample the epicuticular wax layer on pea leaves and hence to analyze the composition of epicuticular crystals exposed at the outermost surface of leaves. The epicuticular layer was found to contain 74% and 83% of the total wax on adaxial and abaxial surfaces, respectively. The platelet-shaped crystals on the adaxial leaf surface consisted of a mixture dominated by hexacosanol, accompanied by substantial amounts of octacosanol and hentriacontane. In contrast, the ribbon-shaped wax crystals on the abaxial surface consisted mainly of hentriacontane (63%), with approximately 5% each of hexacosanol and octacosanol being present. Based on this detailed chemical analysis of the wax exposed at the leaf surface, their importance for early events in the interaction with host-specific pathogenic fungi can now be evaluated. On adaxial surfaces, approximately 80% of Erysiphe pisi spores germinated and 70% differentiated appressoria. In contrast, significantly lower germination efficiencies (57%) and appressoria formation rates (49%) were found for abaxial surfaces. In conclusion, the influence of the physical structure and the chemical composition of the host surface, and especially of epicuticular leaf waxes, on the prepenetration processes of biotrophic fungi is discussed.

Plant litter and soil type drive abundance, activity and community structure of alkB harbouring microbes in different soil compartments

“…At this time a highly significant impact of the soil type was monitored (Po0.001) while the litter type had no influence. Interestingly, only the relative amount of nonacosane and hentriacontane was influenced by the litter type at this time (Po0.05), which is coincident to earlier results (Avato et al, 1990;Gniwotta et al, 2005).…”

“…Independent of the soil type (P40.1), maize and pea litter differed significantly (Po0.05) in their relative chain-length distribution over time with considerably higher fractions of very long chained alkanes (C 31 -C 40 ) in pea litter. Nonacosane (C 29 ) and hentriacontane (C 31 ), which are known to prevail in maize and pea (Avato et al, 1990;Gniwotta et al, 2005), constituted between 76-97% of the total alkane content in pea litter and 40-62% of the total alkanes in maize (Figure 1). Similar concentration dynamics were monitored for the different soil compartments in both soil types with no significant influence (P40.1) of the litter type over time (Table 2).…”

“…The corresponding cuticulary waxes are produced as protective systems against phytopathogens or to minimise water loss by uncontrolled evaporation (Avato et al, 1990;Gniwotta et al, 2005). Compound concentration and composition of these waxes vary between plants, thus allowing differentiation of several plant families or plants with different metabolic properties like C3 and C4 plants (Rieley et al, 1993;Collister et al, 1994;Maffei, 1996).…”

“…For this, intact soil cores of two arable soils, differing significantly in their composition and texture, were incubated with litter of maize and pea. These two plants were chosen as they represent different assimilation pathways (C3 and C4 plants, respectively) and contain different alkane concentrations as well as different compositions (Avato et al, 1990;Gniwotta et al, 2005). The different compartments were analysed after 2, 8 and 30 weeks of incubation.…”

Estudo molecular do desenvolvimento de <i>Puccinia psidii</i> Winter <i>in vitro</i> e no processo de infecção em<i> Eucalyptus grandis</i>

“…Especificamente, os eventos iniciais do processo de infecção como germinação e diferenciação das estruturas iniciais de infecção do fungo (tubo germinativo, apressório e hifa de penetração) parecem ser desencadeados por propriedades específicas da superfície da planta (GNIWOTTA et al, 2005;IWAMOTO et al, 2002;RINGELMANN et al, 2009;TESSMANN;DIANESE, 2002;TSUBA et al, 2002;ZABKA et al, 2008 …”