Impact of cuticle on calculations of the CO2 concentration inside leaves

Abstract

Water vapor over-estimates the CO 2 entering leaves during photosynthesis because the cuticle and epidermis transmit more water vapor than CO 2 . Direct measurements of internal CO 2 concentrations may be preferred. The CO2 concentration inside leaves (c i) is typically calculated from the relationship between water vapor diffusing out while CO2 diffuses in. Diffusion through the cuticle/epidermis is usually not considered. This study was undertaken to determine how much the calculations would be affected by including cuticle properties. Previous studies indicate that measurable amounts of CO2 and water vapor move through the cuticle, although much less CO2 than water vapor. The present experiments were conducted with sunflower (Helianthus annuus L) leaves in a gas exchange apparatus designed to directly measure c i, while simultaneously calculating c i. Results showed that, in normal air, calculated c i were always higher than directly measured ones, especially when abscisic acid was fed to the leaves to close the stomata and cause gas exchange to be dominated by the cuticle. The effect was attributed mostly to the reliance on the gas phase for the calculations without taking cuticle properties into account. Because cuticle properties are usually unknown and vary with the turgor of the leaf, which can stretch the waxes, it is difficult to include cuticle properties in the calculation. It was concluded that direct measurement of c i may be preferable to the calculations.

Root application of selenite can simultaneously reduce arsenic and cadmium accumulation and maintain grain yields, but show negative effects on the grain quality of paddy rice

“…A reduction in stomatal conductance generally inhibits transpiration in plants (Boyer, 2015). However, both the Se(VI) and Se(IV) treatments increased the transpiration rate of the rice leaves in the present study, which is inconsistent with the reduction in the stomatal conductance.…”

Temperature responses of photosynthesis and leaf hydraulic conductance in rice and wheat

“…Then the measurements of gas exchange and K leaf were conducted at 20 and 35°C. C i may be overestimated when g s is low under drought stress (Boyer, ), which can further affect the estimation of g m . Therefore, cuticular conductance ( g cut ) of Shanyou 63 and Yannong 19 was measured to recalculate C i and g m in plants under drought stress.…”

Using the rapid A‐Ci response (RACiR) in the Li‐Cor 6400 to measure developmental gradients of photosynthetic capacity in poplar

“…It is important to consider the implications of g s for RACiR and A/C i measurements. Several studies (Boyer, 2015a(Boyer, , 2015bTominaga & Kawamitsu, 2015;Tominaga, Shimada, & Kawamitsu, 2018) show that C i is overestimated due to cuticular conductance to water. Due to the rate of RACiR, the bias in C i due to cuticle conductance should be less variable relative to standard A/C i measurements, because g s is less variable.…”