TY - JOUR

T1 - Russeting partially restores apple skin permeability to water vapour

AU - Khanal, Bishnu P.

AU - Ikigu, Godfrey M.

AU - Knoche, Moritz

N1 - Funding information: This research was funded in part by a grant from the Deutsche Forschungsgemeinschaft (Grant no. KN 402/15-1). We thank Friederike Schroeder and Simon Sitzenstock for technical support. We also thank Yun-Hao Chen and Jannis Straube for preparing the microtome sections and Dr. Sandy Lang for helpful comments on an earlier version of this manuscript.

PY - 2019/3/8

Y1 - 2019/3/8

N2 - Main conclusion: The higher water loss of russeted fruit results from the higher permeance of the periderm of the russeted skin as compared to that of the intact cuticle and epidermis. Apple fruit surfaces are often in-parallel composites, comprising areas of intact cuticle (atop a healthy epidermis) adjacent to areas covered by periderm (so-called russet). The occurrence of non-russeting and russeting genotypes makes this species an ideal model to study the barrier properties of its composite skin. The objective was to quantify the water vapour permeances of non-russeted (P ES ) and russeted fruit skins (P PS ). Rates of water loss from whole fruit (F fruit ) and excised epidermal skin segments (ES) or peridermal skin segments (PS) were quantified gravimetrically. The F fruit was larger in russeting than in non-russeting genotypes because P PS exceeded P ES by about twofold. Also, the P ES of russeting genotypes was larger than that of non-russeting genotypes. Generally, P PS was more variable than P ES . These differences were consistent across seasons and genotypes. The lower P ES as compared to P PS resulted primarily from the higher wax content of the cuticle of the P ES . For non-russeted genotypes, the value of P ES was significantly related to the permeance determined on the same intact fruit (P fruit ). Close relationships were also found between the F fruit calculated from P ES determined on the same fruit and the measured F fruit . For russeting genotypes, the P ES or P PS were not correlated with P fruit . The F fruit calculated from P ES , P PS , A ES and A PS (all determined on an individual-fruit basis) was significantly correlated with the measured F fruit . Our results demonstrate that the periderm permeance exceeds the cuticle permeance and that permeances of non-russeted surfaces of russeting genotypes exceed those of non-russeting genotypes.

AB - Main conclusion: The higher water loss of russeted fruit results from the higher permeance of the periderm of the russeted skin as compared to that of the intact cuticle and epidermis. Apple fruit surfaces are often in-parallel composites, comprising areas of intact cuticle (atop a healthy epidermis) adjacent to areas covered by periderm (so-called russet). The occurrence of non-russeting and russeting genotypes makes this species an ideal model to study the barrier properties of its composite skin. The objective was to quantify the water vapour permeances of non-russeted (P ES ) and russeted fruit skins (P PS ). Rates of water loss from whole fruit (F fruit ) and excised epidermal skin segments (ES) or peridermal skin segments (PS) were quantified gravimetrically. The F fruit was larger in russeting than in non-russeting genotypes because P PS exceeded P ES by about twofold. Also, the P ES of russeting genotypes was larger than that of non-russeting genotypes. Generally, P PS was more variable than P ES . These differences were consistent across seasons and genotypes. The lower P ES as compared to P PS resulted primarily from the higher wax content of the cuticle of the P ES . For non-russeted genotypes, the value of P ES was significantly related to the permeance determined on the same intact fruit (P fruit ). Close relationships were also found between the F fruit calculated from P ES determined on the same fruit and the measured F fruit . For russeting genotypes, the P ES or P PS were not correlated with P fruit . The F fruit calculated from P ES , P PS , A ES and A PS (all determined on an individual-fruit basis) was significantly correlated with the measured F fruit . Our results demonstrate that the periderm permeance exceeds the cuticle permeance and that permeances of non-russeted surfaces of russeting genotypes exceed those of non-russeting genotypes.

KW - Cork

KW - Cuticle

KW - Microcrack

KW - Periderm

KW - Wax

UR - http://www.scopus.com/inward/record.url?scp=85056857325&partnerID=8YFLogxK

U2 - 10.1007/s00425-018-3044-1

DO - 10.1007/s00425-018-3044-1

M3 - Article

C2 - 30448863

AN - SCOPUS:85056857325

VL - 249

SP - 849

EP - 860

JO - Planta

JF - Planta

SN - 0032-0935

IS - 3

ER -