Researcher affirms 86-year-old hypothesis

WSU researcher affirms 86-year-old hypothesis
Washington State University biologist Michael Knoblauch measured and counted thousands of microscopic holes to test an 86-year-old hypothesis of how nutrients are moved in a plant. Here he is with a microscope photo of a sieve plate that separates the elongated cells of a plant's vascular system. Credit: Washington State University

A Washington State University biologist has found what he calls "very strong support" for an 86-year-old hypothesis about how nutrients move through plants. His two-decade analysis of the phenomenon has resulted in a suite of techniques that can ultimately be used to fight plant diseases and make crops more efficient.

Some 90 percent of the food we consume at one time went through a plant's phloem, the vascular system that carries sugars and other nutrients from leaves, where they are produced by photosynthesis, to roots and fruits. But scientists know so little about how this works, said Michael Knoblauch, professor in the WSU School of Biological Sciences, that they're like cardiologists who haven't learned about the heart.

"If you have a little-supported hypothesis that is central to plant function, it's a problem," he said. "For example, take plant-insect interactions. Aphids feed on the system. If we don't understand how the system works in detail, we cannot find new strategies to kill aphids. Plant viruses also move through the system."

The fundamental principle of phloem transport was published by Ernst Münch in 1930. While his hypothesis is intuitive and elegant, it does not appear to account for the extreme pressure needed to move fluid in something as large as a tree. Münch left that to others to figure out.

"He came up with the hypothesis because he knew how solute-driven flow could work," said Knoblauch. "But he was not into measuring all these things or finding evidence for his hypothesis."

To make his finding, published in the journal eLife, Knoblauch spent more than 20 years devising ways to look inside a living plant without disrupting the processes he was trying to measure and describe.

WSU researcher affirms 86-year-old hypothesis
Washington State University biologist Michael Knoblauch made hundreds of thousands of measurements in three morning glories to test an 86-year-old hypothesis of how nutrients flow through plants. Credit: Washington State University

"It's super-tough to work with this tissue," he said. "It's a technical question. It's really difficult to access it and this has always fascinated me."

He measured flow velocities with fluorescent dies and radioactive isotopes. With his son, Jan, a second author on the paper and a WSU sophomore, he developed a "picogauge" that could measure extremely sensitive phloem pressures.

He looked at tomatoes, fava beans, kelp off the British Columbia coast and a red oak in the Harvard Forest in central Massachusetts. With various microscopes—he directs WSU's Franceschi Microscopy and Imaging Center—he measured the circumferences of not only plant stems but the ciabatta-like holes of sieve plates that separate elongated cells in the phloem tissue.

The cell geometries were particularly critical, as an order-of-magnitude change in the diameter of a tube or hole creates a four-order change in the volume delivered to the roots or fruits.

For his eLife studies, he made roughly 100,000 measurements in each of three morning glory plants he grew alongside WSU's five-story Abelson Hall.

In addition to building the evidence for a long-held , Knoblauch hopes his work can find new ways to protect plants. It might also lead to ways of making the energy in biofuels easier to concentrate and access.

"If we can tell the phloem, 'OK, store it here, where we can easily harvest it,' it will be a big step forward," he said.

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More information: Michael Knoblauch et al, Testing the Münch hypothesis of long distance phloem transport in plants, eLife (2016). DOI: 10.7554/eLife.15341
Journal information: eLife

Citation: Researcher affirms 86-year-old hypothesis (2016, June 6) retrieved 18 July 2019 from
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Jun 06, 2016
"If we can tell the phloem, 'OK, store it here, where we can easily harvest it,' it will be a big step forward," he said.

More Monsanto GMO speak.

Jun 07, 2016
Except companies are not mentioned, and artificial selection is everywhere. (Don't argue for cleanliness then, soap was a big health step forward before vaccines, which is "more Monsanto GMO speak"! Every time you wash with soap you disrupt prokaryote cell membranes, and make the genes insert into cells that manage to heal their membranes and survive - you are your own GMO technician.)

Jun 07, 2016
Accessing those delicate systems is real-neat work !!

Uh, should it have been tracer 'dyes' ? IIRC, 'dies' is either expiry-related, or devices for forming an external shape or thread...

Jun 07, 2016
There's a whopping sized difference between reprogramming a plant's physical shape and growth pattern than there is in a natural skin healing process. We both know this. What happened to your old OM status, by the way?

Jun 10, 2016
The ad hominem argument is alive and well as ever.

There are legitimate questions to ask about GMOs, but you're not doing it telefrenetic. You actually expect people at a science site to say, "Oh, yeah. Monsanto. Bad."

They do lots of questionable things, as do most corporations, but I see you taking a point by point basis with most. I know you can think better than a simple ad hominem, so I have to conclude we have yet another example of ego identity, group affiliation driven, working backwards from an a priori conclusion and fraudulently presenting it as an objective a posteriori conclusion.

You know the devil is in the details. I and every other self sufficient farmer has been creating GMOs for centuries. Yeah, that's not what you're talking about, which is why you need to clean up your language and say what you actually mean. Which data would be incomprehensible to your ego identity group- hence the logical fallacy being your best shot.

Jun 10, 2016
Haven't you heard? Intellectual integrity is dead. Affiliation groups come with a raft of their own facts these days and they are not open to falsifiable testing. You either "get it" or you're "not down with it". It's like we've gone back to Aristotelian psychology. The mind directly apprehends the formal essence of a thing via the passive intellect. Minds intuit the right answer and it is right because the formal essence is not perceived, it is an irreducible truth.

Funny how those types often think of themselves as Renaissance people. Renaissance thinkers are spinning in their graves at the return to freakin' Aristotle.

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