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Groping for the master switch.

Groping for the Master Switch

In 1959, a diverse group of scientists at the Beltsville Agricultural Research Center carried out the first spectrophotometric measurement of phytochrome. Two of the key ingredients were the Pioneering Research Laboratories created by USDA in 1957.

These two labs, each created around an outstanding scientist, applied the concept of giving that scientist freedom to lead the lab into any research problem of interest.

One of the pioneering labs was built around Harry Borthwick, the other, around Sterling Hendricks. These two researchers, who had been collaborating for several years, could now work without the restrictions that so often creep into organizational structures.

A third key ingredient was the creation of the Instrumentation Research Laboratory within USDA's Agricultural Marketing Service and located in the Beltsville Agricultural Research Center's Building 002. I had the privilege of serving as the leader of the instrumentation lab, and I was able to convince my administrators that my research team should have freedom to work on projects not directly related to the lab's assigned mission.

A few convenient steps from 002 were buildings 006 and 007, which housed Hendricks and Borthwick. I became acquainted with Hendricks because he had a supply of lenses, mirrors, and other optical devices we could borrow for our projects. I subsequently hired Warren Butler, a biophysicist with a keen interest in plant physiology. He quickly became acquainted with Hendricks, Borthwick, and Bill Siegelman, who joined Borthwick's lab in 1957.

Without an assigned boss, this group became the team that found and measured phytochrome, succeeding where previous attempts to extract the pigment had failed. We had developed instrumentation to measure the optical properties of dense light-scattering samples, so we began a search for the elusive pigment using spectrophotometry of plant tissues.

Our initial attempts concentrated on fluorescence techniques. We did so because we knew the pigment had to be at a very low concentration, and we believed these techniques could best measure low concentrations.

Early in 1959, we abandoned this approach. We'd found that the fluorescence of chlorophyll and its derivatives masked any evidence of the photoperiod pigment. So we switched to trying to detect the change in absorption spectra that Hendricks had predicted in previous experiments on a wide range of plant material. We searched for plant material low in chlorophyll and other interfering pigments and high in the photoperiod pigment.

Siegelman and Hendricks had found a relationship between photoperiod response and anthocyanin formation, so we began to explore dark-grown seedlings that showed the presence of anthocyanin.

After several failures, one day Hendricks appeared in our laboratory with several dishes of dark-grown turnip seedlings for Butler and me to test. Working in the dark with a dim green light source, we packed plant tissue from the seedlings into the sample cell and measured the absorption spectrum.

Hendricks, a mountain climber, then took the sample cell, jumped up on the lab bench, and held the sample close to the fluorescent lamp to irradiate it with red light. Again we measured the absorption spectrum, and we could see that it had changed.

Next we irradiated the sample with a flashlight covered with several layers of colored film. The film blocked red light but transmitted far-red. Again we measured the absorption spectrum, with three pairs of eyes intently watching the pen on the recorder, each of us mentally trying to push the pen up as it passed the 660 nanometer region and down as it passed the 730 nm region. We could see a difference!

We irradiated again with red light and recorded the spectrum. To our delight, we had reversibility: red light decreased the absorption in the 660-nm region and increased the absorption in the 730-nm region. Far-red light did the opposite. We tested the sample several times and then called Siegelman so he could begin the extraction procedure.

The story of phytochrome detection illustrates one type of team research - an unstructured one. While this was the best way to solve the specific problem we faced, is it generally the best way to do research?

I think the answer must be no. Today and in the future, researchers will continue to rely on team approaches to solve many problems. From an administrative standpoint, however, organized teams are required. Still, administrators should avoid doing anything to discourage informal cooperation among researchers.

And we should always be alert to the possibility that an unorganized team - working together for the joy of finding new knowledge - can get the job done.

Karl Norris was part of the Beltsville research team that succeeded in 1959 - after an intensive quest - in detecting the plant pigment phytochrome, which serves as a biological light switch that controls flowering and other plant functions. In this month's Forum, he tells of the teamwork that made the discovery possible.

Norris went on to refine the spectrophotometer, an instrument now highly regarded in research and for many commercial applications. It operates on the principle that measuring the light passed through an apparently opaque object can reveal information about the object's unseen interior.

Now retired, Norris is a consultant for ARS and a collaborator with scientists at Johns Hopkins University developing a noninvasive device to monitor the content of oxygen in blood flowing to the brain.
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Title Annotation:discovery of plant pigment phytocrome
Author:Norris, Karl
Publication:Agricultural Research
Date:Sep 1, 1991
Words:874
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