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John Sperry

Professor Emeritus

Ph.D. Harvard University


Research Statement

As humans, we are acutely aware of the importance of maintaining vascular function. To plants it is no less critical. My laboratory investigates hydro-vascular structure and function in plants in relation to their ecology, physiology, and evolution. Plant water transport is a phenomenal process. The sheer quantity of water moved through plants often exceeds river flow on a watershed scale. The plant's xylem tissue carries all of this water to the leaves where it evaporates and influences regional weather patterns. The conspicuous consumption of water by plants is the price they pay for obtaining CO2 from the atmosphere through their open stomata. The transport is driven by negative liquid water pressure, a remarkable fact that will always irritate physicists. Just as stress is the nemesis of vascular function in humans, it also disrupts plant water transport. Water- and freezing stress cause "cavitation"... a type of vapor-lock that disrupts the negative sap pressure and creates a non-conducting gas embolism in the vasculature. When water uptake and transport are threatened by cavitation, the plant closes its stomata to protect its vascular system at the expense of photosynthesis. Extreme stress events lead to mortality, and vascular failure is directly or indirectly a major factor. Our research investigates plant water transport as a major control on both plant (and ecosystem) productivity, and plant survival.

Selected Publications

  • Venturas MD, Hacke UG, Sperry JS (2017) Plant xylem hydraulics: what we understand, current research, and future challenges. Journal of Integrative Plant Biology. DOI: 10.1111/jipb.12534
  • Sperry JS, Venturas MD, Anderegg WRL, Mencucinni M, Mackay DS, Wang Y, Love DM (2017) Predicting stomatal responses to the environment from the optimization of photosynthetic gain and hydraulic cost. Plant Cell and Environment 40: 816-830 (Solicited article for special issue on water transport)
  • Tai X, Mackay DS, Anderegg WRL, Sperry JS, Brooks PD (2017) Plant hydraulics improves and topography mediates prediction of aspen mortality in southwestern US. New Phytologist 213: 113-127
  • Smith DD, Sperry JS, Adler FR (2017) Convergence in leaf size vs. twig leaf area scaling: Do plants optimize leaf area partitioning? Annals of Botany 119: 447-456
  • Wolfe B, Sperry JS, Kursar T (2016) Does leaf shedding protect stems from cavitation during seasonal droughts? A test of the hydraulic fuse hypothesis. New Phytologist 212: 1007-1018