Cuticle permeability is an important parameter for the trade-off strategy between drought tolerance and CO uptake in land plants.

To protect against water loss, land plants have developed the cuticle; however, the cuticle strongly restricts CO uptake for photosynthesis. Controlling this trade-off relationship is an important strategy for plant survival, but the extent to which the changes in cuticle affects this relationship is not clear. To evaluate this, we measured CO assimilation rate and transpiration rate together in the mutant (), which exhibited marked evaporative water loss due to an increased cuticle permeability caused by a new allele of (). Under high humidity (85%) conditions, the mutant exhibited higher CO assimilation rate in exchange for decreasing water use efficiency by one-third compared to the ) mutant, whose stomata are continuously open. Our results indicate that the increased cuticle permeability in affects transpiration rate more than CO assimilation rate, but the effect on CO assimilation rate is larger than the effect of open stomata in , suggesting that the cuticle permeability is an important parameter for the trade-off relationship between drought tolerance and CO uptake in land plants.