Cutin and Cutan Biopolymers: Their Role as Natural Sorbents

Abstract

The aliphatic biopolymers cutin and cutan are important precursors of soil organic matter. In this study, we examined the effects of these biopolymers' decomposition and transformation in the soil on their sorptive properties. The levels of cutin and cutan decreased by 35 and 30%, respectively, after 20 mo of incubation. Carbon‐13 nuclear magnetic resonance and differential scanning calorimeter analyses suggested that the rigid (crystalline) polymethylene moieties of cutan decompose with time. This observation is in contrast to previous reports, which suggested that this alkyl‐C moiety is resistant to biodegradation. Cutin, however, exhibited mainly decomposition of the mobile (amorphous) polymethylene moieties. Moreover, some of its degraded materials were transformed into humic materials. The phenanthrene sorption coefficient decreased by 80 and 37% with incubation time of the cutin and cutan samples, respectively. For 1‐naphthol, the sorption capacity decreased by 90% due to cutin decomposition. With cutan, this parameter did not show any changes correlated with incubation time. Phenanthrene exhibited linear and reversible sorption isotherms. In contrast, pronounced desorption hysteresis was obtained for 1‐naphthol with the 20‐mo‐incubated cutin sample and with all cutan samples. With all cutan samples, desorption hysteresis increased with decomposition. Our data suggest that the sorptive nature of both biopolymers was affected by soil decomposition. With degradation, the role of cutin as a natural sorbent decreases while cutan acts as a natural highly efficient sorbent for organic compounds in the soil.

Decoupling the direct and indirect effects of climate on plant litter decomposition: Accounting for stress‐induced modifications in plant chemistry

“…Environmental perturbations also lead to changes in the chain‐length distributions in waxes (Shepherd & Griffiths, ), which is evident in plants adapted to warmer and drier climates, such as the Mediterranean, with these plants showing a greater proportion of longer chain (C34‐C37) alkanes in their waxes than plants adapted to cooler and wetter climates (Dodd & Poveda, ). Because of the depolymerization susceptibility of the ester linkages in cutin, this polymer is labile, whereas cutan and crystalline waxes are more recalcitrant and hydrophobic (Boom et al., ; Shechter, Xing, & Chefetz, ; Stimler, Xing, & Chefetz, ). Thus, along with the quantitative increase in cuticular matrices, the acclimation by plants to stressful climates could be caused by increases in cutan and crystalline waxes in the cuticle.…”

Degradation of Plant Cuticles in Soils: Impact on Formation and Sorptive Ability of Humin-Mineral Matrices

“…In intact cuticle or in soils amended with cuticle that have been incubated for shorter periods of time (i.e., <24 mo), the OC is probably less tightly attached to the mineral matrix, and fewer condensed and rigid domains are available for phenanthrene sorption. This would explain the more linear isotherms observed in previous studies (Chefetz, 2007; Shechter et al, 2010; Stimler et al, 2006).…”

“…Because cutin is an amorphous polyester, its biodegradation is expected to be facilitated as compared with the polyethylene‐like biopolymer cutan (Kögel‐Knabner, 2002). Shechter et al (2010) reported an overall 30% degradation of cutin and cutan incubated for 20 mo with sandy loam soil. In the current study, cuticle degradation of tomato and agave cuticles was much higher (67 and 73%, respectively) for the loamy sand soil, probably due to the presence of more labile OC in the whole cuticle as compared with the isolated biopolymers used by Shechter et al (2010).…”

“…Chefetz (2007) reported a 30% decrease in sorption affinity of phenanthrene to sandy soils during incubation with tomato and pepper cuticles. Similarly, Shechter et al (2010) showed decreases of 60 and 10% in the organic C normalized soil–water partition coefficient for organic compounds ( K OC ) values for phenanthrene sorption on purified cutin (obtained from tomato fruit) and cutan (obtained from agave leaves), which were incubated with sandy soils for 20 mo. Another study (Stimler et al, 2006) showed little or no effect of decomposition of tomato and pomelo cuticles incubated for 9 mo with sandy soil on the sorption of phenanthrene to that soil.…”

“…The decrease in sorption efficiency of phenanthrene was related to decomposition of the cutin biopolymer. Thus, cuticles that contained sufficient amounts of cutan exhibited a much lower decrease in K OC values due to the high efficiency of cutan as a natural sorbent and its resistance to biodegradation (Chefetz, 2007; Shechter et al, 2010).…”