Michael J. Kasperbauer was born and raised on a grain-livestock farm near Manning, Iowa. He attended a one-room rural school near the family farm, Manning High School, and Iowa State University. After a tour of duty with the U.S. Army Signal Corps, he returned to Iowa State University in 1956 to begin graduate study. While a graduate student he taught laboratories and lectured in both crop production and plant physiology, and did research on the role of daylength and temperature in seasonal regulation of shoot and root growth of biennial sweetclover. During that same period a research team led by Sterling Hendricks and Harry Borthwick at Beltsville identified a photoreversible growth regulatory system that they called phytochrome.
In 1961, Kasperbauer received the Ph.D. degree with a joint major in plant physiology and agronomy-crops under the co-direction of Walter E. Loomis and Iver J. Johnson, and a minor in botany with John Sass. After completing his Ph.D., he followed the advice of Professor Loomis and did postdoctoral study and work with Drs. Hendricks and Borthwick at the USDA-ARS Pioneering Research Laboratory for Plant Physiology at Beltsville. The first year was as a National Science Foundation Postdoctoral Fellow, and the second year as the National Academy of Science/National Research Council Resident Research Associate at the Pioneering Research Lab.
A few days after Kasperbauer arrived, Dr. Hendricks demonstrated the spectrograph that he had designed and built from spare, surplus, and borrowed parts in the 1940's (see diagram).
The surplus carbon arc light source had served as the spotlight at a nearby vaudeville theatre in the early 1900's. The light was beamed through a narrow vertical slit and through two large prisms that were borrowed from the Smithsonian, where they had been stored after being used by Samuel P. Langley (1834-1906), a renowned physicist, astronomer, and aeronautics pioneer. The "rainbow" of colors was displayed on the treatment table where Drs. Hendricks, Borthwick, and colleagues had treated many soybean and cocklebur plants to determine effectiveness of different colors of light in control of flowering enroute to the discovery ofphytochrome. They had also studied photoreversible control of germination of light-requiring lettuce seeds.
Following the demonstration, Kasperbauer asked whether they would consider using smaller test plants to get more data points and greater precision -- which might be important if the information was to be used in future field crop production systems. It was a natural question because he had already observed that an Iowa strain of pigweed could be induced to flower at less than one-inch in size on short days, whereas it would grow to several feet if kept on long days. Within a few days, Dr. Borthwick found a small seed supply of a related weed species, Chenopodium rubrum. Exploratory experiments were done by Kasperbauer to compare early responsiveness of pigweed, chenopodium, and a few other species. The pigweed and chenopodium were about equal, but the available chenopodium seed supply was greater. Kasperbauer developed pre-treatment, treatment, and post-treatment protocols for chenopodium as a tiny test plant for use on the spectrograph. That included development of a numerical rating scale based on microscopic viewing of the shoot apex a week after completion of treatment on the spectrograph. The next photograph shows the colors of the spectrum and a tray of tiny chenopodium seedlings (rows were less than an inch apart) ready for treatment on the spectrograph.
Within the next year and a half there were many experiments to test different exposure durations, energy levels, timing of dark-reversion of phytochrome, and efficiency of different wavelengths (colors) of light. All three scientists were actively involved in design, conduct, and interpretation of every experiment with chenopodium on the spectrograph. Very quickly, they developed the most precise action spectrum (efficiency of different wavelengths of light) ever obtained for photo-control of flowering (Botanical Gazette 124:444-451. 1963; 125:75-80. 1964).
Another important benefit of doing research on the spectrograph with Drs. Hendricks and Borthwick was that there was time for informal discussions including a number of "what if" scenarios while waiting for completion of plant exposure times of 10 to 15 min, or longer, in the spectrum. One day Kasperbauer asked what if the light impinged on the lower rather than on the upper surface of the leaf. Initially, Dr. Hendricks dismissed it as not realistic. However, Dr. Borthwick had a few extra cocklebur plants and Kasperbauer did a small-scale experiment. The plant response was the same no matter which surface received the light. Although that experiment seemed a bit "off-the-wall" in 1962, it became highly relevant about 22 years later when Kasperbauer and Patrick G. Hunt began researching possible effects of conservation tillage systems on the light environment of growing plants.
Even though the chenopodium/spectrograph experiments focused on phytochrome control of flowering, Kasperbauer also recorded any unexpected plant responses that were not part of the designed experiment. One such notation was a stem elongation and raised leaf angle response to prolonged exposure to far-red light at longer wavelengths than were thought at that time (1962) to be effective via phytochrome. That notation remained almost forgotten in a notebook until thelate-1960's when he tried to explain why close-spaced seedlings in the field were physically very similar to those that received extra far-red light in a controlled environment.
In 1963, Kasperbauer’s research with chenopodium as a tiny test plant was featured as the cover story on the July issue of Agricultural Research magazine. He and Dr. Hendricks are shown below discussing whole plant phytochrome research near the end of the 2-year postdoctoral period.
Kasperbauer began his USDA-ARS career in 1963 as a Research Plant Physiologist in the Crops Research Unit at Lexington, Kentucky. He conducted laboratory, controlled-environment, and field studies designed to improve tobacco plant to plant uniformity to facilitate production efficiency. The work concentrated on seed germination, control of premature flowering, phytochrome regulation of assimilate partitioning, and leaf chemistry.
The controlled-environment studies with tobacco showed that while red light (R) was critical for germination of light-requiring seed, far-red (FR) was extremely important in the physical development of growing plants. A higher FR/R photon ratio resulted in seedlings with longer stems, higher leaf angles, larger leaf areas, thinner leaves, modified chloroplast structure, altered concentration of photosynthetic pigments, modified chemical composition, and usually a higher shoot/root biomass ratio.
In general, extra FR applied in the controlled environments resulted in plants that were very similar to close-spaced plants growing outdoors, even before the outdoor plants were large enough to shade each other. In the late 1960's he concluded that FR transmitted through and/or reflected from nearby green plants was the dominant variable in phytochrome sensing of plant competition and regulation of plant development to favor survival among the perceived competition. A developmental response to wavelengths of FR reflected from green leaves was also consistent with the earlier notation of unexpected stem elongation and leaf angle responses to the longer wavelengths of FR that he had observed on the spectrograph.
In the mid-1960's he also studied light-mediated regulation of growth at the cellular level in petri dishes on artificial nutrient media. As little as 5 minutes of R per day (alternated with 23 hours and 55 minutes of darkness) resulted in increased nutrient uptake and growth compared to those kept in darkness. The response to R could be negated by 5 minutes of FR indicating phytochrome involvement in nutrient uptake and/or utilization in dividing and recently divided cells. That work was done in collaboration with Dr. Richard Reinert, and the first paper was published in the journal, Nature.
Awareness of the cellular growth response to phytochrome action was useful in developing protocols for culturing haploid plants from immature pollen in anthers excised from tall fescue plants in cooperation with ARS fescue breeder, Robert C. Buckner, in the late 1970's and early 1980's. The nonfertile haploid plants were cloned and field tested for hardiness andforage quality characteristics. Fertile doubled haploid plants were then regenerated from tissue excised from the most desirable haploids by a new tissue culture method that Kasperbauer developed. The doubled haploids were the equivalent of highly inbred lines, which are difficult to obtain in a wind-pollinated, self-infertile plant like tall fescue. The research led to invitations to present his theory and results at the International Grassland Congress in France, and to be editor and co-author of a book, Biotechnology in Tall Fescue Improvement.
At the University of Kentucky he was appointed to the graduate faculty in 1965 and promoted to full professor (adjunct) in 1973. He served on the graduate faculties of both the Plant Physiology and Crop Science Doctoral Programs, initiated the graduate course on Physiology of Plant Growth and Development, served as major professor to four Ph.D. students, and served on advisory committees of about 20 other M.S. and Ph.D. students.
Since 1983, he has been the senior plant scientist at the USDA-ARS Coastal Plains Soil, Water, and Plant Research Center at Florence, SC. He is also a professor (adjunct) in the Department of Plant Pathology and Physiology at Clemson University. His research has expanded to include the effects of row orientation, plant spacing, mulches, and other management variables on the amount of reflected FR and the spectral composition of light received by developing plants; and, this via the phytochrome system on adaptation of the photosynthetic apparatus and on photosynthate partitioning among leaves, stems, roots and seed of soybean, cotton, corn, wheat, tomato, and selected vegetable crops.
Before Kasperbauer arrived in South Carolina in 1983, soil scientist Patrick G. Hunt and colleagues had found that soybean yields were unexplainably higher in north-south rows when they were irrigated and higher in east-west rows when there was occasional water stress. In an early discussion, Kasperbauer recalled his earlier controlled environment experiments in which tobacco seedlings that received a higher FR/R ratio at the end of each day partitioned more growth to shoots and less to roots. With a new high tech portable spectroradiometer, he and Terry Matheny measured reflection from green soybean leaves and found that the reflection reached maximum percentage at about 750 to 760 nm (which was the same waveband that altered stem and leaf growth responses to prolonged FR on the Beltsville Spectrograph in 1962). They also measured spectra of light coming to upper parts of plants and found that those in N-S rows received more FR reflected from adjacent rows and higher FR/R ratios near the end of day. A companion controlled environment study showed that the same cultivar of soybean did indeed partition more growth to shoots and less to roots if they received the higher FR/R ratio at the end of each day. The directional FR reflection from soybean leaves was attributed to heliotropic (sun-tracking) leaves. The 1984 paper in the journal Physiologia Plantarum launched immediate international awareness of the importance of reflected FR in crop production.
Other studies dealing with FR reflection from growing plants and effects on tillering, growth, and yield of wheat and corn were done in cooperation with soil scientist Douglas Karlen in 1984-86. In the photograph below, Kasperbauer is shown discussing the research on importance of reflected FR at the XIV International Botanical Congress in Berlin, Germany.
Next, Kasperbauer and Hunt decided to check the spectra of light reflected from different kinds of dead plant residue used in conservation tillage systems. This was extended to reflection from different colored soils. They are shown examining cotton seedlings growing over insulation panels that were covered with different colored soils.
After about a month, the seedlings had larger shoots (and less massive roots) when grown over brick-red soil (which reflected very little blue light and a high FR/R ratio) versus those grown over white soil.
When it was apparent that seedlings of many different plant species responded to color of upwardly reflected light over different colored soils and plant residues, the studies expanded to painted panels. Plants responded the same to a given reflection spectrum whether they were over soil or paint.
Dr. Dennis Decoteau, a new horticulturist at the nearby Clemson Pee Dee Research Center, asked Kasperbauer and Hunt if he could join in for a field test with tomato in 1986. Standard black plastic over trickle irrigation served as the control treatment. A range of upwardly reflected spectra was obtained by painting some of the plastic. Early crop yields were higher over red-painted plastic than over the standard black. It was quickly found in subsequent experiments that the yield response sometimes differed over red paints that looked the same, but reflected different amounts of FR.
Many different colors of painted plastic were examined for reflection spectra and those reflecting a range of FR/R ratios and quantities of blue light were field tested with a number of shoot and root crops. Kasperbauer and his assistant, Woodrow Sanders, are shown measuring reflected light in field plots.
Patent applications for the colored mulch technology were filed, the technology was licensed to Sonoco Products Co. of Hartsville, SC, and a Cooperative Research and Development Agreement was established between ARS and Sonoco to facilitate development of the technology. Kasperbauer prepared an "ideal" reflection spectrum for crops such as tomato and strawberry based on his career research. In cooperation with Sonoco, this resulted in development of a red plastic that reflects a spectrum favoring yield of tomato and strawberry. Tomato plants growing over the new red plastic are shown below.
Strawberry yields were higher and most "taste testers" preferred berries that grew and ripened over the red mulch.
The red mulch is manufactured by Sonoco and marketed by Ken-Bar Agricultural Plastics of Reading, MA, as Selective Reflective Mulch (SRM-Red). It is marketed through many catalogs and supply stores and has been tested extensively, including an evaluation versus standard black mulch by Consumer Reports in 1997. They recommended it for tomato in their April 1998 issue. Kasperbauer and Hunt received the Award for Excellence in Technology Transfer from the Federal Laboratory Consortium in 1998, and from ARS in 1999.
In addition to effects on yield, reflected light from colored mulches can alter flavor, nutrient, and other quality characteristics of plant products. Results of some cooperative research with scientists at Kentucky State University on flavor components such as concentrations of glucosinolates and sugars in turnip have already been reported. Other studies of quality components are in progress with cooperators at other locations.
Dr. Kasperbauer was elected Fellow of the Crop Science Society of America in 1985 and Fellow of the American Society of Agronomy in 1986. He received the Crop Science Research Award in 1990, the L.M. Ware Research Award in Horticulture in 1990, and the Agronomic Research Award in 1994.