Giant trees have no trouble pumping water to top branches: new research
New research on water transport in giant trees has revived questions about how they move sap to great heights without traditional pumps and despite the physical limits of suction. Commenters contrast cohesion–tension theory, capillary action and evaporation-driven “pulling” with ideas like segmented pumping or wind-driven motion, and note that cavitation and gravity likely set an upper bound on tree height around 100–130 meters. The exchange also touches on ecological adaptations such as fog and moss water uptake, and on how understanding these mechanisms could inform future bioengineering and plant science.
Mechanism of Water Transport (Pumping vs Sucking)
- Several comments stress that trees do not “pump” water like a mechanical pump; they mainly “draw” it via low pressure at the top.
- The cohesion–tension model and capillary action are repeatedly cited: evaporation in leaves creates tension, pulling a continuous water column up xylem vessels.
- It’s noted that xylem is dead tissue, with no active pumps or valves, contradicting ideas of “pumps in series.”
- Some push back on oversimplified popular explanations, reminding that a simple suction column in open air cannot lift water beyond ~10 m; capillaries and negative pressure change that picture.
- There is mention of trees operating at several bars of negative pressure and the challenge of avoiding cavitation.
Height Limits and Gravity
- Skeptics argue the new research conflicts with earlier work showing strong limits on maximum height (~130 m) from water transport and gravity.
- Others suggest water transport might not be the sole limiting factor; mechanical strength of wood and other constraints are also invoked.
- Speculative ideas appear: different evolutionary pressures (e.g., megafauna damaging saplings, human activity, nutrient depletion) might explain why trees are not taller today; these are presented as conjecture, not established fact.
Alternative Water Sources and Adaptations
- Fog capture in coastal redwoods and possible mutualism with moss (holding moisture on branches) are discussed as ways to supplement water, especially at height.
- Leaves and moss absorbing water directly from rain or fog is seen as a way to bypass long-distance transport for some needs.
- Desert and evergreen adaptations (e.g., reduced transpiration, CAM photosynthesis) are mentioned as strategies to manage water loss.
Structured / Exclusion-Zone Water Debate
- One line of discussion introduces “structured water” or exclusion-zone (EZ) water as a possible contributor to sap flow driven by radiant energy.
- Others respond cautiously, noting that while interfacial water phenomena are real, specific EZ claims are contested and subject to critical reviews.
Attitudes Toward the Research and Plant Science
- Some dismiss the paper as confirming the obvious (big trees clearly get water to their tops), but acknowledge that incremental, non-controversial work is common.
- Multiple commenters express strong interest in botany, plant physiology, and computational/technical approaches to agriculture, framing plant biology as a major frontier.