Whole-plant hydraulics as a regulator of systemic signaling and stress response

Plants possess signaling systems that span their tissues to coordinate whole-organism responses to abiotic perturbations (e.g., heat, light, drought, nutrient deficiency) and biotic stresses (e.g., pathogen infection). This communication network of Systemic Acquired Acclimation (SAA) signals relies on coupled hydromechanical processes (the transmission of water, chemical species, and pressure waves through the xylem and phloem) and electrophysiological signaling. A recent poroelastic model (Bacheva et al.) suggests that the role of hydraulics in long-distance signaling, and downstream responses such as cytosolic calcium waves, is strongly influenced by whole-plant water relations, including wound type, wound location, evaporative demand, and vascular architecture.

In this work we extend the model to account for the bio-chemical dynamics of the calcium signal and show the importance of such models for understanding the underlying mechanisms of plant communication pathway. Using gene-encoded calcium reporters in Arabidopsis we test the model predictions. We quantitatively compare signal propagation speed and distal-leaf arrival under different hydraulic regimes (transpiring vs. non-transpiring plants). Finally, by varying the wound type (dry vs. wet cut), we demonstrate control of signal arrival and, in turn, the downstream response of the plant.

Bacheva et al. - 10.1073/pnas.2422692122