Document: CHA-3-66-31

Carbon dioxide as a selective agent for stomatal density.

REID, C.D.* and R.JACKSON

Duke University, Durham, NC 27708 USA ¹

Abstract:
In long-term elevated CO₂, adaptive responses may include decreased stomatal density with decreasing leaf conductance. To our knowledge no study includes a test, under controlled conditions, of such an evolutionary selection, although reports from herbarium specimens indicate that stomatal density has changed with atmospheric [CO₂]. To elucidate whether adaptation to different [CO₂] affects stomatal density, we grew Arabidopsis at pre-industrial, ambient, and elevated atmospheric CO₂ (260, 360, and 700 l l^-1, respectively) at 800 E m^-2 s^-1for a 13-hr photoperiod and 22C:18C day:night. We used seeds from a previous single-generation field experiment where we identified plants with low (Lo) or high (Hi) stomatal density (avg. 208, and 545 stomates mm^-1, respectively) relative to the average population (407 stomates mm^-1; control). The stomatal index (SI) of control plants decreased significantly with increasing [CO₂] (0.130, 0.118, and 0.100 stomate per epidermal cell [ec] at 260, 360 and 700 l l^-1, respectively) because ec density increased with [CO₂] while the stomatal density remained unaltered. For Lo plants, SI also decreased significantly from 260 to 360 l l^-1(0.130 and 0.115 stomate per ec) because of changing ec density. In contrast to herbaria studies, in constant environments, our data suggest that increasing [CO₂] has little effect on stomatal density but decreased SI because of increasing ec density. As SI was not correlated with leaf area, a CO₂ effect at cell initiation is suggested.

Keywords: Arabidopsis, elevated CO₂, stomatal index

This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.