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Title: Making space for the pore: Stomatal movement when guard cells and epidermal cells interact
Abstract: Stomatal pores of vascular plants are holes on the surfaces of leaves that can open and close. Their role in modulating plant gas exchange is to increase carbon dioxide uptake, while preventing excessive dehydration and loss of xylem function due to cavitation. Two stomatal mechanisms have been described. The first, reported to occur in the majority of ferns and all lycophytes, creates small, slit-like pores due to changes in the shape of guard cells. The second, reported in angiosperms, succeeds in increasing gas exchange capacity by moving both guard cells and adjacent epidermal cells and forming pores wider than would be possible with only guard cell movements. This seminar explores the variability in stomatal regulation caused by guard-epidermal cell (GC/E) interactions in angiosperms. First, I present a visual characterization of guard-epidermal interactions as stomatal pores form in Vicia faba and Tradescantia virginiana. Then, I discuss how the influence of epidermal cells on stomatal regulation is not only widespread among angiosperms but also variable. Finally, I examine the risks to leaf dehydration when the influence of epidermal cells causes ‘wrong way’ (WWR) stomatal opening under conditions of sudden water loss. I find that the magnitude of water loss from WWR decreases with drought. The results of this research clarify that every step of stomatal opening in angiosperms is a result of guard-epidermal cell interactions. Advancing our understanding of GC/E dynamics is essential if we are to integrate tissue level responses of stomata into an understanding of plant-environmental interactions at all scales.
Committee: Missy Holbrook (Advisor), Ned Friedman, Elena Kramer (Chair), Tony Rockwell