• Holbrook Lab Grad student, Zhe He, working in the lab

  • Melissa showing some of her baby Nolana mollis!

  • Melissa and Sophie matching at Ponkapoag Bog on Fall Bog Crawl 2022

  • Sophie bending maples in the greenhouse to simulate wind!

  • Sophie using a microtome (salami meat slicer for science) on tree stems to turn them into very small sections for staining.

  • Sophie using a microtome (salami meat slicer for science) on tree stems to turn them into very small sections for staining.

  • Unintentional twins, Zhe and Sophie!

Welcome!

Welcome to the Holbrook lab! We study the physics and physiology of vascular transport in plants with the goal of understanding how constraints on the movement of water and solutes between soil and leaves influences ecological and evolutionary processes. Currently, we are working on questions relating to cavitation, stomatal mechanics, solute transport, cell wall mechanics, and wood anatomy.

 

 

 

Latest News

Congratulations Melissa!

August 18, 2023
The Holbrook lab would like to congratulate Melissa Mai for winning the Best Poster prize at the Harvard Biophysics Fall Retreat for her poster "Two-way Traffic: An Architectural Model of Competing Flows in Pine Needles"!

Congratulations Dan!

August 18, 2023
The Holbrook Lab is happy to congratulate Dan Buonaiuto for successfully defending his Ph.D. thesis, "Phenological sensitivity as a mediator of plant interactions." We know you're going to do incredible things!

Farewell Yakir!

July 13, 2023
Farewell and good luck to Yakir Preisler, who is leaving Harvard to start his own lab at the Volcani Center this fall. It has been an absolute honor and joy to have him be a part of the Holbrook group for the past few years. We will miss you, but we know you are going to do great things!
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Recent Publications

Johnson, Kate M, Sophie R Everbach, N. Michele Holbrook, and Mark E Olson. 2023. “Evaluating Carlquist’s Law from a physiological perspective.” IAWA Journal. Publisher's Version Abstract
“Carlquist’s Law” is a striking pattern of association between anatomical features in the wood of vessel-bearing plants. It derives from Sherwin Carlquist’s observation that xylem vessels tend to be solitary when embedded in a matrix of imperforate tracheary elements that appear to be conductive, whereas xylem vessels tend to be grouped when surrounded by seemingly non-conductive cells. Vessel-vessel contacts (vessel grouping) allow water to travel between conduits, but also provide pathways for air to propagate from embolized (air-filled) vessels into functional vessels. If the background matrix is conductive, it is conceivable that water could bypass embolized vessels, providing an alternative transport route in species with conductive backgrounds and solitary vessels. Much remains to be tested in this hypothesis, including the topology of the vessel networks in species with solitary versus grouped vessels and how conductive the different imperforate tracheary element types are. Exploring Carlquist’s Law promises to provide key insight into the causes of embolism in plant conduits, the modes of embolism passage between conduits, and how vessels and the cells in which they are imbedded may interact to govern the pathways of water flow through plants.
Losada, Juan M, Zhe He, and N. Michele Holbrook. 2022. “Sieve tube structural variation in Austrobaileya scandens and its significance for lianescence.” Plant, Cell & Environment 45 (7): 2460-2475. Publisher's Version Abstract
Lianas combine large leaf areas with slender stems, features that require an efficient vascular system. The only extant member of the Austrobaileyaceae is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulics, but the vascular phloem continuum aboveground remains understudied. Microscopy analysis across leaf vein orders and stems of Austrobaileya scandens revealed a low foliar xylem:phloem ratio, with isodiametric vascular elements along the midrib, but tapered across vein orders. Sieve plate pore radii increased from 0.08 µm in minor veins to 0.12 µm in the petiole, but only to 0.20 µm at the stem base, tens of metres away. In easily bent searcher branches, phloem conduits have pectin-rich walls and simple plates, whereas in twining stems, conduits were connected through highly angled and densely porated sieve plates. The hydraulic resistance of phloem conduits in the twisted and elongated stems of A. scandens is large compared with trees of similar stature; phloem hydraulic resistance decreases from leaves to stems, consistent with the efficient delivery of photoassimilates from sources under Münch predictions. Sink strength of a continuously growing canopy might be stronger than in self-supporting understory plants, favoring resource allocation to aerial organs and the attainment of vertical stature.
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