Chemical Composition of Cuticle and Barrier Properties to Transpiration in the Fruit of Clausena lansium (Lour.) Skeels

Abstract

The plant cuticle, as a lipid membrane covering aerial plant surfaces, functions primarily against uncontrolled water loss. Herein, the cuticle chemical composition and the transpiration of wampee fruit (Clausena lansium (Lour.) Skeels) at the green, turning, and yellow stages in cultivars of "Jixin" and "Tianhuangpi" were comprehensively studied. The coverage of wax and cutin monomers per unit of fruit surface area at the green stage was lower in "Jixin" than in "Tianhuangpi" and increased gradually during development. Cutin monomers accumulated ranging from 22.5 μg cm^-2 (green) to 52.5 μg cm^-2 (turning) in "Jixin" and from 36.5 μg cm^-2 (green) to 81.7 μg cm^-2 (yellow) in "Tianhuangpi." The total composition of waxes ranged between 6.0 μg cm^-2 (green) and 11.1 μg cm^-2 (turning) in "Jixin," while they increased from 7.4 μg cm^-2 (green) to 16.7 μg cm^-2 (yellow) in "Tianhuangpi." Cutin monomers were dominated by ω-, mid-dihydroxy fatty acids (over 40%), followed by multiple monomers of α,ω-dicarboxylic acids with or without added groups, α-monocarboxylic acids with or without ω- or mid-chain hydroxy or mid-epoxy groups, primary alcohols, and phenolics. The very-long-chain (VLC) aliphatic pattern of cuticular waxes was prominently composed of n-alkanes (ranging from 21.4% to 39.3% of total wax content), fatty acids, primary alcohols, and aldehydes. The cyclic waxes were dominated by triterpenoids (between 23.9 and 51.2%), sterols, and phenolics. Water loss in wampee fruit exhibited linear changes over time, indicating an overall monofunctional barrier to transpiration. Permeance for water in wampee fruit was higher at the green stage than at the yellow stage in both "Jixin" and "Tianhuangpi," which showed a negative correlation with the changes of VLC n-alkanes. The results showed the cuticular chemicals, including cutin monomers and waxes, in wampee fruit and further indicated the potential contributions of the cuticular chemical composition to the physiological functions in fruits.

Keywords: barrier properties; cuticular waxes; cutin monomers; transpiration; wampee fruit.

Figure 1

Changes in fruit appearance and surface area changes at different developmental stages for wampee (Clausena lansium (Lour.) Skeels). The overall changes of “Jixin” —JX (A), and “Tianhuangpi” —THP (B), as well as the fruit surface areas (C) at the green, turning, and yellow ripe stages. Data are presented as the mean ± standard deviation (n = 12). Scale bars in (A) and (B) are 1 cm. Different letters indicate the significant differences at the level of 0.05.

Figure 2

The overall cuticular chemical composition in wampee fruit (Clausena lansium (Lour.) Skeels). Total cuticular waxes (A) and total cutin monomers (B) in the three developmental stages of “Jixin” —JX and “Tianhuangpi” —THP. Data are presented as the mean ± standard deviation (n = 5). Different letters indicate the significant differences at the level of 0.05.

Figure 3

Chemical compositions of cutin monomers in wampee fruit (Clausena lansium (Lour.) Skeels). Fruits at the green, turning, and yellow stages of two cultivars (A) “Jixin” and (B) “Tianhuangpi” were comparatively analyzed. Data are given as means ± standard deviation (n = 5). Different letters indicate the significant differences at the level of 0.05.

Figure 4

Chemical compositions of cuticular waxes in wampee fruit (Clausena lansium (Lour.) Skeels). Fruits at the green, turning, and yellow stages of two cultivars (A) “Jixin” and (B) “Tianhuangpi” were comparatively analyzed. Data are given as means ± standard deviation (n = 5). Different letters indicate the significant differences at the level of 0.05.

Figure 5

Carbon chain-length distribution and content of aliphatics in wampee fruit (Clausena lansium (Lour.) Skeels). (A,B) fatty acids, (C,D) primary alcohols, and (E,F) n-alkanes in fruits at the green, turning, and yellow stages of “Jixin” and “Tianhuangpi” were comparatively analyzed, respectively. Data are given as means ± standard deviation (n = 5). Different letters indicate the significant differences at the level of 0.05.

Figure 6

Changes in sterols and triterpenoids as cyclic pattern in wax mixtures of wampee fruit (Clausena lansium (Lour.) Skeels). Fruits at the green, turning, and yellow stages of two cultivars (A) “Jixin” and (B) “Tianhuangpi” were comparatively analyzed. Data are given as means ± standard deviation (n = 5). Different letters indicate the significant differences at the level of 0.05.

Figure 7

(A,B) Transpiration in wampee fruit (Clausena lansium (Lour.) Skeels) at the green, turning, and yellow stages of “Jixin” —JX and “Tianhuangpi” —THP. Data are given as means ± standard deviation (n = 15). Different letters indicate the significant differences at the level of 0.05.