Marc Carriquí

First of all, why is all this important? The evolution of trees is considered a turning point in the history of the Earth, as this transformed the land surface into the vegetated state we know today (no = no forests! Obvious, right?).pic.twitter.com/SoJAIb1olT

Until our paper has been published (today!) it was thought that bryophytes (= non-vascular land plants) have never (ever!) managed to achieve tree sizes because they lack these vascular plant components. However…pic.twitter.com/eso01JsUcJ

We provide first and clear evidence that a widespread moss species possesses: An efficient vascular system functionally comparable to that of vascular plants. Capacity to regulate its transpiration to prevent cavitation.pic.twitter.com/QS0dfiApNR

(1.3) Vulnerability of the moss hydroids to water stress-induced cavitation. Cavitation was thought to be exclusive of vascular plants, but this moss cavitates and moreover its vulnerability is within the vascular plant spectrum. Watch how our moss cavitates:pic.twitter.com/pUebr60LPO

(2) The moss is capable to dramatically reduce its water diffusive conductance in response to increasing evaporative demand to protect itself from cavitation. Gas exchange regulation was directly associated with stomata but this moss regulates without stomata!pic.twitter.com/CxIGEulQFq

So…what really allows vascular plants and not mosses to evolve trees? Rather than an integrated and efficient vascular pipeline, it appears that what disables all bryophytes to emerge far from the soil level is their inefficient exchange ratio of water for photosynthetic CO2pic.twitter.com/Wn2NtG9GtU

We propose that vascular plant innovations associated with improvement in water use efficiency, like cuticle formation, the efficient location of stomata and high mesophyll conductance to CO2, are more fundamental to the evolution of vascular plants than the vascular system.pic.twitter.com/cjhFKyQQ5R

[Bonus tweet 1/3] Our little and desiccation tolerant moss can rapidly transition from a dehydrated to a completely functional state by REFILLING its hydroids after a light rain (take that trees!). Look at how water pushes air bubbles in the hydroids thanks to capillarity!pic.twitter.com/nHdE79pqYQ

[Bonus 2/3] Amazed? Wait for it! At the end it seems that all the air has been removed. However, there remain small bubbles of compressed air that must dissolve in water if the moss remains hydrated. What happens if the moss dehydrates before these bubbles disappear?pic.twitter.com/stvYunEQLQ

[Bonus 3/3] Effectively, the air bubbles expand BUT in a much smoother and leisurely way than the catastrophic and flash way of cavitation.pic.twitter.com/fxYgLcs596