Plasticity of the Cuticular Transpiration Barrier in Response to Water Shortage and Resupply in Camellia sinensis: A Role of Cuticular Waxes

Abstract

The cuticle is regarded as a non-living tissue; it remains unknown whether the cuticle could be reversibly modified and what are the potential mechanisms. In this study, three tea germplasms (Wuniuzao, 0202-10, and 0306A) were subjected to water deprivation followed by rehydration. The epicuticular waxes and intracuticular waxes from both leaf surfaces were quantified from the mature 5th leaf. Cuticular transpiration rates were then measured from leaf drying curves, and the correlations between cuticular transpiration rates and cuticular wax coverage were analyzed. We found that the cuticular transpiration barriers were reinforced by drought and reversed by rehydration treatment; the initial weak cuticular transpiration barriers were preferentially reinforced by drought stress, while the original major cuticular transpiration barriers were either strengthened or unaltered. Correlation analysis suggests that cuticle modifications could be realized by selective deposition of specific wax compounds into individual cuticular compartments through multiple mechanisms, including in vivo wax synthesis or transport, dynamic phase separation between epicuticular waxes and the intracuticular waxes, in vitro polymerization, and retro transportation into epidermal cell wall or protoplast for further transformation. Our data suggest that modifications of a limited set of specific wax components from individual cuticular compartments are sufficient to alter cuticular transpiration barrier properties.

The Tea Plant Leaf Cuticle: From Plant Protection to Tea Quality

“…Since the cuticle is generally regarded as a nonliving tissue, the question is whether the cuticle modification is reversible once the stress conditions (such as drought) have disappeared. Zhang et al (2021) reported that wax coverage and cuticular transpiration barriers indeed are reinforced by drought, but can be reversed following rehydration treatment (Figures 4A,B). There are multiple potential nonexclusive mechanisms working together to regulate cuticular wax deposition, including in vivo wax synthesis or transport in epidermal cells, dynamic phase separation between the EWs and the IWs, in vitro polymerization (Spencer et al, 1988), and retro transportation into epidermal cell wall or cytoplasm for further transformation (Figure 5; Zhang et al, 2021).…”

“…Another advantage of the TEM method is that the cuticle thickness on the adaxial and the abaxial surface can be measured simultaneously. Zhang et al (2021) applied the TEM method and measured the cuticle thickness of the fifth leaf from eight different tea germplasms, and the data were summarized in Table 1. The average thickness of the adaxial cuticle is in the range of 2.12-2.99 µm and the abaxial cuticle thickness is in the range of 1.24-1.46 µm.…”

“…Cuticle structure and wax composition can also be affected by environmental factors such as drought (Chen et al, 2020;Zhang et al, 2021). Even though the tender leaves and the mature leaves have profound differences in cuticular wax chemistry, drought stress induces both types of leaves with some common compositional changes in cuticular waxes.…”

“…(2) Does the wax subcompartment localization affect its contribution to the transpiration barrier property? To address these questions, Zhang et al (2021). Zhang et al (2020) grew three tea germplasms in a greenhouse.…”

Water Sorption and Desorption of Isolated Cuticles From Three Woody Species With Focus on Ilex aquifolium

“…A mixture of different long-chain aliphatic molecules, such as alkanes, alcohols, aldehydes, fatty acids, and esters, are present in the cuticle, together with variable amounts of cyclic compounds (Jetter and Riederer, 2016 ). There is controversy about the role of intra- vs. epi-cuticular waxes as barrier to leaf transpiration (Jetter and Riederer, 2016 ; Zeisler-Diehl et al, 2018 ; Zhang et al, 2021 ), but recent evidence suggests that their importance may be specific to leaf side (Zhang et al, 2020 ) and species, which respond plastically to drought (Chen et al, 2020 ; Sanjari et al, 2021 ). Additionally, variable amounts of phenolic compounds have been recovered in the cuticle of different organs and plant species (Karabourniotis and Liakopoulos, 2005 ; España et al, 2014 ).…”