Differential Occurrence of Cuticular Wax and Its Role In Leaf Tissues of Three Edible Aroids of Northeast India


 Localization of cuticular wax (CW) on the leaf epidermis and its interaction with physiological mechanisms of three edible aroids, Alocasia, Colocasia, and Xanthosoma, were assessed. Scanning electron microscopy depicted the occurrence of CW in the leaf tissues, which was higher in Colocasia (10.61 mg dm-2) and Xanthosoma (11.36 mg dm-2) than in Alocasia (1.36 mg dm-2). Higher CW in Colocasia and Xanthosoma strengthened leaf epidermis and improved the physiological processes compared to Alocasia. CW acted as a protecting barrier against deleterious solar radiation in terms of sun protection factor (SPF). The glossy appearance of wax crystals in the Alocasia leaf cuticles resulted in higher SPF. The occurrence of CW was directly related to leaf chlorophyll stability, moisture retention ability, and cellular membrane integrity in the leaf tissues. Colocasia exhibited superhydrophobic properties with higher static contact angle (CA) >150o than hydrophobic Xanthosoma, and Alocasia with CA ranged between 99.0o to 128.7o. Colocasia CW highly influenced the qualitative and protective mechanisms of the leaf. Aroids are the cheapest sources of edible CW among the terrestrial plants, which could be used in food, agricultural and industrial applications.


Introduction
Aroids are important minor food crops, belong to the Araceae family, cultivated widely in the tropics of the world 1,2 . Edible aroids are one of the cheapest sources of carbohydrates and dietary energy; thus, they have social and economic signi cance on daily nutrition intake for about 400 million people around the world 3 . Despite a low share among the tuber crops, production of aroids exceeded 10.13 million tonnes worldwide 4 .
About 105 genera and 3040 species of aroids are available globally, out of which 146 species are found in India, north-eastern states in particular 5 . Ethnobotanical importance of 32 wild and cultivated aroid species of the genus Alocasia, Amorphophallus, Colocasia, Homalomena, Lasia, and Monstera were reported from north-eastern India 5 . Alocasia and Colocasia are cultivated widely in this region, whereas, Amorphophallus, Homalomena, Lasia, and Monstera were reported in limited marshy and wetland of Assam state. In a eld ethnobotanical research study, Alocasia, Colocasia, and Xanthosoma were identi ed as the three major cultivated edible aroids in north-east India 6 . Leaves, pseudo-stems, and corms of these three aroids are consumed as vegetables and traditional medicines by the tribal communities of the north-eastern hill region of India 7,8 . These aroids were used as folk medicines in the ancient world 9 due to their high antioxidant, anti-in ammatory, anti-nociceptive, and anti-carcinogenic properties 10,11 . Apart from the food and medicinal uses, aroids have many possible applications as animal feed, carbohydrates, energy, and waxes for various industrial uses 12 . Aroid starch could be a substitute for 40% of the biodegradable plastics 13 . Aroids contain higher cuticular wax (CW) in the leaf tissues among the terrestrial plants, which still need to be explored. Preliminary reports indicated that Colocasia leaf bio-wax has potential hydrophobic surface coating substances 14,15 . Plant-derived hydrophobic and non-toxic edible waxes have ample scope in food industries, especially for food protection and preservation 16 . The wide use of carnauba, beeswax, or petroleum-based waxes in food industries warrants consumer's preference and health hazards 17 . Aroids are widely cultivated under harsh environments 3 , and exploration of edible wax from cheaply available natural resources would add momentum to the food and post-harvest industries 18 . Cuticular wax (CW) in leaf tissues acts as a protective barrier against several biotic and abiotic factors 19 such as adverse solar radiation and ultraviolet (UV) penetration, drought and cold injury, bacterial, fungal, and insect infestations 20 . CW in leaf cuticles forms plant-environment interface and plays an important role in photosynthesis, osmoregulation, and leaf gas exchange. Lipophilic CW coating on the leaf cuticle enables the plants to prevent the dehydration caused due to non-stomatal water loss, prevents chlorosis, maintains leaf pigmentation, and deters membrane injury caused by various environmental factors and invaders 21 . Zeisler-Diehl et al. (2018) 22 reported the biosurfactant and protective function of plant cuticular wax and its interaction with epiphytic microorganisms in different crops. However, CW protects against leaf blight disease in aroids like Colocasia caused by the most pro cient fungal pathogen Phytophthora colocasiae Racib. (Pc) 23 have not yet been assessed.
Despite being an essential biological constituent, studies on the role of cuticular wax in leaf tissues of aroids are limited. A clear understanding of CW constituent on eco-physiological events in leaf tissues of edible aroids needs to be established to further explore and utilize potential aroid bio-wax. The present study was focused on the role of cuticular wax in the leaf tissues of three different aroid species cultivated in the north-eastern hill region of India. The information on hydrophobicity, sun protecting factor, antifungal agents etc. would be useful to harness the prospects of CW from edible aroids as a potential source of water repellent agent, UV protection lm, targeted agrochemicals emulsions, food coating, packaging material, and encapsulating agents in food and pharmaceutical industries. May-June 2020 at 8-9 am and processed for wax estimation and leaf characters analyses immediately.

Scanning electron microscopy (SEM) of aroid leaves
Scanning electron microscopy (SEM) was performed to observe epicuticular wax microstructure on the fresh leaves of Alocasia, Colocasia, and Xanthosoma. Samples were cross-sectioned using a scalpel, mounted on the holders, and coated with gold particles as described by Pieniazek and Messina (2017) 24 . Microscopic visualization of wax crystals was performed using a scanning electron microscope (JOEL-JSM 6390LV, Japan) at a magni cation of 500X, 1000X, 1500X, and 2000X. Brightness and contrast are the most important variables that need to be controlled during the acquisition of images; therefore, the values of these parameters were kept constant for each magni cation during image acquisition 25 . The element composition of these waxes was analyzed using SEM with an energy dispersive X-ray (EDX) system.

Extraction and estimation of cuticular wax
The leaf surface area was measured using Image J software 24 before wax estimation. The wax extraction process was optimized by submerging the leaves in 99.9% chloroform 14 (HiMedia, India) in a glass Petri plate (Borosil, India) for 15, 30, 45, 60, 90, 120, and 180 seconds. The extract was kept under a laminar air ow (Labtop Instruments Pvt. Ltd., India) until the chloroform was evaporated. The wax particles were carefully collected by scrapping with a scalpel 14 . Eight different leaves (n=8) of each aroid species were taken for wax estimation. The experiment was repeated thrice. The results were calculated using the following equation.Waxcontent = Ww LA Where, W w is the weight of the wax in mg, and LA is the leaf area in cm 2 .

Sun protection factor (SPF)
The wax extracted from the three aroid species were dissolved in methanol (HiMedia, India) at different concentrations (4.0 mg ml −1 , 2.0 mg ml −1 , 1.0 mg ml −1 and 0.5 mg ml −1 ). The absorbance of different wax concentrations was recorded in a UV-Vis spectrophotometer (Eppendorf, Germany) every 5 nm at 290 to 320 nm 27 . SPF was calculated using the following equation, Where, Abs is the absorbance of the samples, CF is a correction factor (=10), and EE(λ) x I(λ) is the product of the erithermal e ciency spectrum and the solar simulator intensity spectrum, which was

Contact angle and wettability
After wax extraction (n=8 each), fresh and dewaxed leaves were attened upon a white surface with transparent tape. A drop of Milli-Q water (10 µl) [Merck, India] was placed on the surface of the leaves with and without wax. A digital camera with a macro lens was placed perpendicularly to the sample to capture the image. The contact angle was estimated using Image J software 24 . The experiment was repeated thrice with three replications.
In order to observe the wettability, the extracted wax was dissolved in chloroform (HiMedia, India) at different concentrations (100 mg ml −1 , 75 mg ml −1 , 50 mg ml −1 , 25 mg ml −1 and 0 mg ml −1 ). About 0.25 ml of each concentration was poured on 3x3 cm 2 lter paper pieces and allowed to evaporate the chloroform under a laminar hood (Labtop Instruments Pvt. Ltd., India). The lter paper without wax coating (0 mg ml −1 ) was used as a control. Once the chloroform was completely evaporated, 10 µl of Milli-Q water (Merck, India) droplet was placed on the center of the wax-coated lter paper pieces. The time until the water droplet was completely absorbed was measured using a stopwatch. The live video of the absorbed water droplet on the wax-coated paper pieces was recorded by a video camera at 1080x720 pixels.

Chlorophyll content (Ch) and chlorophyll stability index (CSI)
Fresh leaf samples of Alocasia, Colocasia, and Xanthosoma were collected from the ICAR RC NEHR farm and cut into 5x5 cm 2 pieces. The sample pieces were submerged at 56°C for 30 min in a water bath containing Milli-Q water (Merck, India) to determine the pigment stability against the control sample submerged in Milli-Q water at room temperature (25°C). Chlorophyll content (Ch) of the control samples (ChC) and the hot water treated samples (ChT) were observed using a SPAD-502 portable leaf greenness meter (Minolta Corp, Romsey, NJ). CSI was calculated following the equation as derived by Mohan et al.

Colour parameters
Leaf samples of the three aroids with wax and after removal of wax were illuminated using a lamp (TL-D Deluxe, 169 Natural Daylight, 18W/965, Philips, NY, USA) with a color temperature of 6500 K 170 (D65, standard light source) and a color-rendering index (Ra) close to 90% 28 .
Eighteen images from one side of each sample and eight regions of interest of each image were taken on the matte black background using the camera settings; 174 manual modes with the lens aperture at the focus of 4.5 and speed 1/125, no zoom, no ash, 175, 3088×2056 pixels resolution and stored in JPEG format.
The image segmentation and color quanti cation were processed by Adobe Photoshop CS6 (v18.0 Adobe Systems Incorporated, 2012, USA). l, a, and b values were transformed to CIE l*, a*, and b* using the Page 6/18 algorithms 28 .
2.8. Relative water content (RWC) and leaf moisture loss RWC and leaf moisture loss were determined following the methods of Perez-Perez et al. (2007) 29 and Bueno et al. (2020) 30 , respectively. Eight leaves of each aroid were cut into squares (5x5 cm 2 ) using a scalpel and weighted to obtain the fresh weight (FW).
Leaves were submerged in Milli-Q water (Merck, India) at 25°C for 4 h to obtain the turgid weight (TW), and the samples were dried in a hot air oven (REMI, India) at 70°C for 96 h. RWC was calculated using the following formula, FW, TW, and DW were fresh weight, turgid weight, and dry weight of the leaf samples, respectively. To measure leaf moisture loss, the wax and dewaxed leaf samples were placed in a laminar air ow (Labtop Instruments Pvt. Ltd., India). The declined leaf weight was measured at 15 min intervals for 240 min using an electronic balance (Shimadzu Analytical, India).

Cell membrane injury (CMI)
CMI was determined by comparing the electric conductivity (EC) of waxed and dewaxed leaves submerged in Milli-Q water (Merck, India) for 22 h followed by 2 h of hot water treatment at 70°C. The electrolytic leakage related to the cell injuries was estimated with the variation on the conductivity 31 as follows: C 1 and C 2 are the EC of the water before and after submersion of leaves for 22+2 h, respectively. T 1 and T 2 are the EC of the water before and after submersion of leaves for 22 h with hot water treatment for 2 h, respectively.  32 . Fresh leaves were collected from the Alocasia, Colocasia, and Xanthosoma plants and wiped with moist cotton, and wax was extracted following standard procedure 14 . The fresh and dewaxed leaves were placed in the Petri plate with moist lter paper (Whatman no.1) at room temperature (25±2°C). Phytophthora colocasiae (Pc) spores were collected from the infected Colocasia leaves with an artists' paintbrush (size#1) in 10 ml of Milli-Q water. The leaves with and without wax were inoculated with 10 µl of Pc spore suspension (15000 ml −1 spores) on the dorsal surface of the leaf. Pc infectivity was observed at different time points at 2, 4, and 6 h.

In vitro Phytophthora colocasiae (Pc) infectivity assay
Infected leaves were immersed in 1.5 ml trypan blue solution for 1 h. The leaves were then decolorized in 98-100% ethanol until green tissues became colorless, and the ethanol was discarded. Each leaf was mounted on a glass slide with the help of 50% glycerol and viewed under a light microscope (Magnus Opto Systems, India). The experiment was conducted thrice with three replications.

Statistical analysis
All the data were analyzed by analysis of variance (ANOVA) in a completely randomized design (CRD) using XLSTAT statistical software (XLSTAT Premium 2020.2.1, Adinsoft, NY). Differences among the mean values were compared using Tukey's test 33 and were considered statistically signi cant when p≤0.05.

Surface properties, extraction process, and estimation of cuticular wax
Leaf surface properties were visualized with SEM before wax extraction (Fig. 1A). Electron micrographs showed the localization, distribution, and abundance of needle-like tubular wax crystals on the aroid leaves. In the present study, we have optimized the wax extraction process for the three aroid species by submerging the leaf pieces in chloroform for 1 min to obtain pure white wax crystals. The time point beyond 1 min resulted in green coloration of the solvent due to the removal of leaf chlorophyll. Upon extraction, CW concentration varied signi cantly among Alocasia (1.36 mg dm −2 ), Colocasia (10.61 mg dm −2 ) and Xanthosoma (11.36 mg dm −2 ) leaf samples (Fig. 1B). Colocasia and Xanthosoma leaves exhibited 10-fold higher CW than Alocasia, which was well visualized in the leaf ultrastructure (Fig. 1A).
Wax microstructures were broad, aggregated, and observed in radiated cluster forms in Xanthosoma, which was different from the wax crystals of Alocasia and Colocasia (Fig. 1C). The wax crystals derived from Alocasia represented rough, irregular, but glossy surface properties. However, Colocasia leaf wax exhibited a smooth, compact, and opaque appearance. Xanthosoma leaf wax illuminated a bright and oral appearance with a friable texture (Fig. 1C). Despite lower wax content, Alocasia elucidates a shiny leaf surface than Colocasia and Xanthosoma, probably due to glossy wax crystals. The quality and quantity of wax content in the leaf epidermis, its elemental composition, and crystallization pattern represent the leaf surface properties and the protecting capacity 34 .
The element composition of these three waxes indicated carbon and oxygen as the two major constituents as observed through the EDX system ( Supplementary Fig. 1). Alocasia wax comprised of 52.89 weight % (w%) of carbon and 39.86 w% of oxygen along with low weight % of magnesium (0.51 w%), sulfur (0.32 w%), chlorine (2.1 w%), and potassium (4.33 w%). However, Colocasia wax comprised 79.94 w% of carbon and 20.06 w% of oxygen, and Xanthosoma wax constituted 86.63 w% of carbon and 13.37 w% of oxygen ( Supplementary Fig. 1). The fresh aroid leaves also comprise similar carbon (49, 57.56, and 59.07 w%) and oxygen (45.96, 39.14, and 38.19 w%) in Alocasia, Colocasia, and Xanthosoma, respectively (data not shown). The previous reports suggested that the composition of carbon in para n wax and beeswax varied from 10.33-12.99 w% and 11.14-17.62 w%, respectively 35 . However, the oxygen composition ranged between 0-0.13 w% in para n wax and 0.40-0.67 w% in beeswax. In our study, Colocasia wax showed better structural and elemental properties than Alocasia and Xanthosoma, which was also comparatively higher than in para n wax and beeswax available commercially 35 . The higher elemental composition in aroid waxes indicated the need for further comprehensive characterization of chemical compounds using GC-MS and/or nuclear magnetic resonance (NMR).

Sun protection factor (SPF)
SPF increased signi cantly (p≤0.05) with an increasing concentration of wax in three aroid leaves (Fig.  2). Alocasia registered a higher mean SPF (2.02) when compared to Xanthosoma (1.35) and Colocasia (0.24). Sun protection activity depends on the ability to prevent the plants from harmful UV radiation-led mutagenesis 36 . Higher SPF was positively correlated with the protective mechanisms and negatively correlated with the adverse effect of UV radiations 37 .
Natural plant substances are considered potential resources for UV protection. In a pilot study, the SPF values were assessed between 0.4-23.5 in different plant species 38 . Eucalyptus showed a higher SPF of 23.5, which was positively correlated with the higher phenolic content 39 . Our results revealed that Alocasia leaves showed 10-fold higher SPF than Colocasia and 2-fold higher SPF than Xanthosoma, which could be explored as a potential natural sun protector. Alocasia exhibited a shiny leaf surface with higher oxygen, sulfur, and potassium, resulting in higher SPF (Supplementary Fig. 1). In an aliphatic chain (sul de) or with a double bond with oxygen (sulfoxide), sulfur induces a glossy leaf surface by accumulating bio-oil and bio-wax, which act as a natural sun protector 40 . Static CA >90 o and <150 o was considered as hydrophobic 41 . A surface with static CA of more than 150 o is regarded as superhydrophobic 42 , probably due to micro and nanoscale hierarchical topography in the leaves. According to the classi cation 42 , Colocasia leaves represented superhydrophobicity similar to the 'Lotus' hydrophobic state, a special state of Cassies's superhydrophobic state 25 . Xanthosoma exhibited a transitional hydrophobic condition between Wenzel's and Cassie's state. However, Alocasia showed Wenzel's form with the lowest static CA and inadequate hydrophobic capacity due to lower wax content and irregular distribution of CW. Results showed that the hydrophobic properties diminished once the wax was removed from the leaves indicating the role of cuticular wax in static CA and hydrophobicity.

Wettability
The wettability test showed the capacity of CW to repel environmental water and protect the leaf surface. In our study, the lter paper pieces coated with aroid wax persisted the water droplets signi cantly (https://drive.google.com/ le/d/1mCbXUAHV_t9E-HLN4OzO5zntJZF7dC9J/view?usp=sharing ). Results showed that lter paper without wax coating instantly absorbed the water droplet compared to the lter paper coated with aroids wax. The resistivity varied signi cantly (p≤0.05) among the three types of aroid wax coating.
The wettability test witnessed higher wax concentration correlated with higher water resistance and hydrophobicity. The above video showed that Colocasia wax coating resisted the water droplet longer, which justi ed its superhydrophobicity. On the other hand, Alocasia and Xanthosoma wax which showed poor hydrophobicity with low water droplet resistance. Uniform wax distribution and regular surface topography with inadequate pore space in Colocasia wax coating were reasoned for better wettability. Oner and McCarthy (2000) 43 reported that wettability is correlated with synthetic compounds, hydrophobicity, and surface topography. Leaf cuticular wax lm was also successfully examined as a model hydrophobic system 44 provides insights for the future potential of edible aroid leaf-based bio-wax lm in food coating.

Chlorophyll content and chlorophyll stability index (CSI)
Signi cant differences (p≤0.05) in chlorophyll content and stability index were observed among the Alocasia, Colocasia, and Xanthosoma leaves. Higher SPAD values for chlorophyll content (55.9) were obtained for Colocasia, followed by Xanthosoma (34.4) and Alocasia (12.6) (Fig. 4A). In dewaxed leaves, SPAD values decreased signi cantly (p≤0.05) in Xanthosoma (27.3), Colocasia (25.8), and Alocasia (9.2). Colocasia exhibited higher CSI, followed by Xanthosoma and Alocasia (Fig. 4B) while exposed to hot water treatment. CW layer in Colocasia protected the cell membrane and prevented the chlorophyll degradation from maintaining CSI. Rapid chlorophyll depletion occurred when the wax was removed from the cuticle, which signi ed the role of CW in maintaining the leaf chlorophyll content. Leaf chlorophyll content 45 and cuticular layer thickness 46 were decreased upon removal of leaf CW due to dismantling of the thylakoid membrane 47 .

Colour Parameters
Colour parameters (l * , a * , and b * values) had signi cant differences (p≤0.05) among the tested aroid leaves with and without wax (Fig. 5). Leaf brightness (l*) decreased when the storage time after defoliation increased. The greenish leaf color was related to a* values, which decreased when the time increased. The decrease in a* value was probably due to the chlorophyll degradation. During leaf pigment degradation, an increase in yellow color (b*) also played a vital role in manipulating leaf greenness.
In the present study, leaf discoloration in Colocasia under dewaxed conditions was higher when compared to leaves with wax. Dismantling of wax crystals from the leaf cuticle resulted in faster chlorophyll degradation, which ensured rapid leaf discoloration. Xanthosoma showed similar l * , a * , b * compared to wax and dewaxed leaves. Cuticular wax exhibited a more predominant role in Colocasia leaf protection than in Alocasia and Xanthosoma. Similar results on leaf color pigmentation using a quanti able RGB model were reported by Chen et al. (2020) 48 . The color variation was related to the chlorophyll degradation and other biological, chemical and gas exchange processes occurring during photorespiration 49 . 3.7. Relative water content (RWC) and leaf moisture loss As shown in Fig. 6, RWC varied signi cantly (p≤0.05) in the range of 76.1-94.7% in waxy leaves and 73.1-85.6% in dewaxed aroid leaves. Alocasia leaves with wax recorded higher RWC, followed by Xanthosoma and Colocasia. RWC in dewaxed leaves declined signi cantly in all three aroids. The rate of decrease in RWC in dewaxed Alocasia leaves was relatively higher compared to Colocasia and Xanthosoma. Lower wax content in Alocasia could be attributed to a higher reduction in RWC. In Colocasia and Xanthosoma, the samples showed less decrease in RWC due to the inherent higher wax content.
CW played an essential role in preventing leaf moisture loss up to 95% by strengthening the cuticle permeability 21 . In our study, Xanthosoma leaves exhibited the lowest moisture loss while embedded with CW, rapidly increasing upon removal of CW from the cuticle. Alocasia also showed a similar response in leaf moisture loss as showed in Xanthosoma. The rapid moisture loss occurred due to the lack of wax content or cuticular cracks upon wax removal 50 . On the other hand, Colocasia leaves showed a high dehydration rate in wax and dewaxed conditions related to the leaf ultrastructure. The location and structural basis of CW is responsible for the cuticular barrier, which restricts moisture loss. On the contrary, stomatal behavior such as opening and closing of stomata also caused reasonable moisture loss, which probably occurred in the case of Colocasia leaves. Rapid moisture loss is one of the major factors that affect leaf quality, and CW helped in leaf moisture retention in the tested aroids.
3.8. Cell membrane injury (CMI) and in vitro Phytophthora colocasiae (Pc) infectivity CW maintains membrane integrity and acts as a protecting barrier against several environmental factors and invaders 50 . In our study, Alocasia leaves showed signi cantly higher CMI while submerged in hot water than Colocasia and Xanthosoma leaves under wax and dewaxed conditions (Fig. 7A). Higher CMI attributed to higher electrolytic leakage of subcellular components in hot water treatment, which was distinctly related to the lower wax content in the leaf tissues of Alocasia. Xanthosoma and Colocasia exhibited lower CMI proportionate to their higher CW.
Leaves of the Aroids, Colocasia, in particular, usually experience leaf blight disease caused by the fungal pathogen Phytophthora colocasiae Racib (Pc). Fig. 7B shows the intensity of in vitro Pc infestation assayed using trypan blue staining. The blue coloration indicated the cellular damage caused by Pc at different time points. Xanthosoma leaves showed less cellular disruption compared to Alocasia and Colocasia. CW outwardly acted as a physical barrier in the leaf epidermis against the invaders. However, Pc releases various cell wall degrading enzymes (CWDEs) such as pectinase, cellulase, and hemicellulase to breach the cell wall components other than CW. In consequence, higher cellular damage observed in Colocasia leaves was probably due to several cell wall constituents such as pectin, cellulose, and hemicellulose. Previous reports also suggested that leaf resistance to Pc is associated with various reactive oxygen species and their scavengers 51 . Higher phenolics in Alocasia and Xanthosoma 52 could also be a major reason for lower Pc infectivity than in Colocasia, illustrated in the trypan blue staining studies.
On the other hand, wax solubility might be another reason for cellular depletion. Nonetheless, the dewaxed leaves showed higher incidence when compared to waxed leaves, which predicted the role of CW on Pc infestation. Several authors 53,54 reported evidence of natural leaf wax in preventing disease incidence. Our results indicated that the presence of CW in leaf tissues sustainably inhibits electrolytic leakage of the subcellular components to maintain the cellular integrity and defends the cellular damage caused by Pc, which was evident by the lower acquisition of trypan blue coloration in the tested aroid leaves.

Conclusions
Signi cant differences among cuticular wax and its interaction between the qualitative and protective mechanisms in leaf tissues of three edible aroids, Alocasia, Colocasia, and Xanthosoma, were observed. Colocasia and Xanthosoma exhibited higher CW similar to Lotus leaves, considered the most pronounced edible wax-rich terrestrial plants. Interestingly, Colocasia leaves showed superhydrophobic surfaces with higher contact angles and better wetting properties suitable for hydrophobic coatings. Higher CW occurrence in Colocasia and Xanthosoma showed signi cant in uence on all the studied leaf properties except SPF. Alocasia exhibited higher SPF despite having lower CW content correlated with the thin and glossy appearance of wax crystals which may be a potent source of natural sun protector. The study results revealed that the leaf cuticular wax coverage in aroids, Colocasia, and Xanthosoma strengthens the leaf epidermis and improves the physiological processes. The evidence provides insight into further exploring the wax structure and composition from the underutilized edible aroids to better understand its food, agricultural and industrial applications. Figure 1 A-C. Leaf ultrastructure of the aroid leaves (Alocasia, Colocasia and Xanthosoma) before extraction of cuticular wax (A); Cuticular wax content of the three aroids (B); Wax structure of the aroids (C).

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