New research published this week, as a collaborative effort between University of Cambridge, University of Sheffield and The John Innes Centre, is changing the way we understand plant ‘breathing’.
On almost every leaf of every plant, tiny active pores called stomata act as channels through which carbon dioxide enters and oxygen leaves the plant; their proper function is essential to the plant but also to animals (as a source of the oxygen we breathe). Each stomate is made up of a pair of cells called guard cells. It has been a long-standing supposition that they function by increasing their internal pressure while having radial reinforcements which force them to form C-shapes, creating a pore between them. The research team behind the work published this week in Current Biology was led by Prof. Andrew Fleming (Univ. of Sheffield) who undertook pivotal experimentation while on sabbatical in Cambridge at The Sainsbury Laboratory in the group of Dr. Siobhan Braybrook.
Utilising the Atomic Force Microscope at The Sainsbury Laboratory to examine guard cell physical properties, a technique whose use in plants was pioneered by Dr. Braybrook, Prof. Fleming and his team uncovered a striking result: stomatal pores in several species display stiffer ends pinning the two guard cells together. Alongside this result, it was observed that not all stomatal cells display radial stiffening in spite of this being the text-book theory for how they open and close.
Modelling efforts at The John Innes Centre revealed that polar stiffening was able to confer excellent opening mechanics to stomata in computational simulations.
These results necessitate a new way of thinking of stomatal pore opening: stiffening the ends of stomata promotes their flexing, allowing them to open efficiently and effectively. Radial reinforcement may not be needed for these special cells to promote plant ‘breathing’.