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Dov
Koller
With Dov Koller’s
passing, plant biology lost a consummate plant physiologist. During
the past several decades, plant biologists have increasingly turned
to molecular tools to investigate important problems in plant biology.
Indeed, many who didn’t fell by the wayside. Dov, however,
was different: He was rightly convinced that there was still a huge
amount to be learned from the whole plant, and he made a brilliant
career based on that premise. Thus, we find paper after paper on
seed germination, photoperiodism, photosynthesis, photorespiration,
and gibberellin responses, all at the organism level.
Dov gradually
began to focus his research on light-driven leaf movements, and
indeed a huge portion of what we know about leaf movement came from
his laboratory. He has left a legacy of more than 125 papers, many
of them seminal.
I first learned
of Dov Koller’s work from an article he cowrote in the Annual
Review of Plant Physiology in 1962 entitled “Seed Germination.”
This beautifully clear review provided an ideal introduction for
teaching this material in my Stanford plant physiology class.
Though I had
met Dov at various meetings, it was only when he came to Carnegie
to spend a sabbatical in my laboratory that I learned what an incredibly
ingenious experimenter he was. By this time, he was fully committed
to studying the mechanism of solar tracking—the way in which
many plants move their leaves to keep them at right angles to incident
light to maximize photosynthesis.
Here are some
of the questions he addressed: Are the photoreceptors oriented?
If a leaf ends up facing the setting sun, what happens the next
morning? Is it still facing west? (No; during the dark period it
reorients to be facing the rising sun in the morning.) How fast
can a leaf move in response to a change in the angle of incident
light? Where are the photoreceptor molecules located? I remember
arguing excitedly with him on one occasion about how a particular
experiment should be done. We finally did the experiment his way,
not mine, and it worked!
He never needed
expensive equipment to address these and many other questions, but
rather built some of the most remarkable contraptions himself from
odd items he could salvage. For example, he mounted a lamp on a
bicycle wheel, properly counterbalanced, so that he could move the
wheel manually to change the angle of incident light striking a
leaf at any rate he wished. This allowed him to demonstrate that
a leaf of Lavatera cretica could move more than 40 degrees per hour,
allowing it to catch the late afternoon sun following a storm.
He also built
an ingenious device that would precisely simulate the angle of the
sun throughout the day so that he could perform his experiments
when all of the leaves were in the same, well-characterized state.
It was his idea to hit a leaf with two light beams—one polarized
in the plane of the main vein and the other at right angles to it—to
see which, if either, would win the physiological tug of war. Naturally,
he built the right device to perform that test and demonstrated
that it is the former. As a result, he discovered the first case
of oriented photoreceptors in higher plants. I still have on my
desk the gadget he built to test whether there were significant
differences in reflectivity for the two beams (an important control;
there weren’t).
Dov was a wonderful
collaborator. He was stimulating, full of ideas, and willing to
spend extra time, sometimes late into the night, to have results
ready for discussion the next day. He was also bursting with infectious
enthusiasm for the science and rigorously applied the highest standards
to the experiments and their interpretation. He always shared our
enthusiasm when things were going well and encouraged us thoughtfully
when they weren’t.
Remarkably,
his scientific thinking remained sharp and perceptive until his
death. Indeed, even while being treated for skin cancer using photodynamic
therapy, he came up with the idea for an ingenious device to improve
the treatment: Use LED-based traffic lights to provide the high-intensity
red light needed to induce the photodynamic effect, but without
burning the patient’s skin. Sadly, although Dov ordered the
traffic lights from China and designed the device, he did not live
to see it built or used. His doctor is now publishing the results
of this successful idea in Dov’s final, posthumous paper.
Besides his
scientific contributions, Dov was also a dedicated educator and
mentor. He trained and nurtured many young people, raising them
to prominent positions in science. He wrote several books to convey
the concepts that he found so beautiful to his students and to a
broader audience. His last manuscript is a summary on his life’s
passion of how and why plants move, a successor to Darwin’s
seminal book on the topic. We hope it will eventually see the light
of day.
My wife Ann
and I have many friends worldwide in the scientific community, but
Dov and his wife Ditza were among the very closest. We treasure
the time we could spend with them, both in and out of the laboratory.
Dov’s passing leaves an aching, empty spot in our hearts and
in those of many others. He will be sorely missed.
Winslow Briggs
Director Emeritus
Carnegie Institution of Washington
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