Cuticular transpiration is not affected by enhanced wax and cutin amounts in response to osmotic stress in barley

Abstract

The plant cuticle, which covers all aerial parts of plants in their primary developmental stage, is the major barrier against water loss from leaves. Accumulation of cutin and waxes has often been linked to drought tolerance. Here we investigated whether cutin and waxes play a role in the drought adaption of barley mimicked by osmotic stress acting on roots. We compared the cuticle properties of cultivated barley (Hordeum vulgare spp. vulgare) with wild barley (Hordeum vulgare spp. spontaneum), and tested whether wax and cutin composition or amount and cuticular transpiration could be future breeding targets for more drought‐tolerant barley lines. In response to osmotic stress, accumulation of wax crystals was observed. This coincides with an increased wax and cutin gene expression and a total increase of wax and cutin amounts in leaves, which seems to be a general response triggered through root shoot signalling. Stomatal conductance decreased fast and significantly, whereas cuticular conductance remained unaffected in both wild and cultivated barley. The often‐made conclusion that higher amounts of wax and cutin necessarily reduce cuticular transpiration and thus enhance drought tolerance is not always straightforward. To prevent water loss, stomatal regulation under water stress is much more important than regulation or adaptation of cuticular transpiration in response to drought.

An SMR cell-cycle inhibitor inducible by a carotenoid metabolite resets root development and drought tolerance in Arabidopsis

“…However, wax and cutin amounts are not always correlated with cuticular transpiration. In barley, osmotic stress increased leaf wax and cutin amounts without any change in cuticular conductance (Shellakkutti et al 2022). In our study too, we could not correlate cutin and wax levels with the changes in cuticular transpiration.…”

Genotype-specific responses to drought stress in Siberian wildrye (Elymus sibiricus): Insights from comparative physiological and transcriptomic analyses

“…Our results indicated a notable increase in wax content under osmotic stress in DT, as opposed to DS. However, Shellakkutti et al 62 discovered that osmotic stress in both cultivated and wild barley led to an increase in wax crystals accumulation, total wax amounts, and wax gene expression, while cuticular conductance remained unaffected.…”

Drought-Induced Changes in Leaf Morphology and Anatomy: Overview, Implications and Perspectives

“…Deposition in the cuticle on the epidermal cells is one of the modifications that plants adopt to enhance tolerance in water-deficient conditions [95]. A positive increase in the thickness was observed in both monocot and dicot plant leaves such as Hordeum vulgare L. [103], Gossypium hirsutum L. [104], Nicotiana Tabacum L. [105], Glycine max L. [106], Triticum aestivum L. [88], Arabidopsis thaliana L. [107] and Sorghum bicolor L. [108] under water stress. However, the thickness of the leaf cuticle is varying among the plant species or even in the same plants under different environmental conditions.…”