Global climate change is occurring much faster than was anticipated at the start of our century, and is now considered a crisis or emergency. Scientists in many fields are working hard to understand how we can adapt to inevitable climate changes, while preserving biodiversity and preventing the collapse of ecosystems. Plant physiology and physiological plant ecology are among the disciplines central to this effort. Scientists in these disciplines study the intricate adaptations that plants have evolved to thrive even in earth’s harshest climates. This knowledge of physiological processes in turn helps biologists understand how entire ecosystems function, and how they maintain their ability to withstand stresses. Plants do not just react to climate change, they also regulate climate. It is vital to know what is happening in the plant kingdom if we wish to predict, and prepare for climate change. The challenge is to try to preserve the resilience of our ecosystems in the years to come, and to maintain food security by protecting important crop species and finding ways to increase their productivity.
Advances in botanical science have depended on many technological innovations, which have brought highly sophisticated techniques to both laboratory and field work. In the mid-twentieth century, a revolutionary concept was to build an integrated complex of greenhouses and laboratories that were fully climate-controlled, so that any set of climatic conditions important for plant growth could be produced indoors. These complexes were dubbed “phytotrons” because botanists thought they represented the equivalent in botany of the cyclotron, or particle-accelerator, in atomic physics – a complicated instrument built at great expense. The first phytotron, which opened in 1949, was the brainchild of Frits Warmolt Went, a plant physiologist and ecologist at the California Institute of Technology (Caltech).
Building a phytotron required a much higher investment in botanical science than was the norm at that time. Caltech’s first botanical laboratory, built in the early 1930s, had cost ten thousand dollars; the phytotron cost over four hundred thousand dollars. Rather remarkably, it set off a world-wide laboratory movement. Botanists were impressed by what they found at Caltech, and within a couple of decades there were phytotrons around the world, with the largest built in Australia, France, and Russia. Although Caltech’s phytotron was torn down in 1972, other phytotrons remained in operation and new controlled-environment complexes continued to be built into the 21st century.
Phytotrons were mainly used for physiological research on plant growth and development, although these laboratories were meant to serve all botanical disciplines. Improvement of crops was one important goal of this research. This was especially the case in the Soviet Union, where the government required botanists to work on plants of economic value. The International Rice Research Institute in the Philippines acquired a phytotron in 1974, and used it to expand research on one of the world’s most important food crops. Scientists were already expressing concern about climate change, and realized they needed to create varieties of rice suited to areas that were not irrigated and were subject to drought. In the 1960s these laboratory innovations sparked a futuristic vision of farming in “food factories” that would be guided by computers, enhanced with space-age technologies, and powered by nuclear energy. Controlled-environment food production was not commercially viable at that time, but has since become commonplace.
Phytotron-based research resulted in one of the most exciting botanical findings of the 1960s, the discovery of what is now known as the C4 pathway for photosynthesis. Marshall D. Hatch and C. Roger Slack made this discovery while studying sugar cane in Brisbane, Australia. The phytotron there, which opened in 1961, was called the David North Plant Research Centre, and was directly inspired by Caltech’s laboratory. Hatch and Slack found that the photosynthetic pathway in sugar cane was different from the known C3 pathway, which Melvin Calvin had elucidated in algae and for which he received the Nobel Prize in Chemistry in 1961. Hatch and Slack’s new model, proposed in 1966, set off a search for the C4 pathway in other species. Further research conducted in another phytotron in Canberra, one of the largest and most elaborate in the world, revealed that the photosynthetic pathway was an adaptation to hot, dry climates, and is found in other crops such as sorghum and maize. In recent years, a scientific goal has been to find a way to introduce the more efficient C4 pathway into C3 rice varieties in order to increase their productivity.
Understanding complex plant adaptations to diverse environments also has ecological significance, helping to explain the distribution and abundance of plant species, one of the central aims of ecology. Ecologists were quick to realize the value of improved laboratories and precision technology for ecological research. Frode Eckardt, a Danish physiological ecologist working in Montpellier, France, had spent time at Caltech in the 1950s, and in 1963 proposed a plan to build an ecological version of the phytotron called an “ecotron” at Montpellier. Funding was not available and the proposal died, but the idea was revived in 1990 when an ecotron opened at Imperial College London’s post-graduate campus at Silwood Park, at a cost of about 1.5 million in U.S. dollars. Ecotrons were designed for experiments on small or mid-sized ecosystems, which could be artificially assembled or could be portions of natural ecosystems transplanted into the laboratory. The first ecotron in the U.S. was the Frits Went Laboratory, which opened in 1995 at the Desert Research Institute in Reno Nevada. Went had moved to Reno in 1965 to head the institute’s new program in desert ecology.
Ecological research benefited from other kinds of laboratory innovations that were inspired by the concept of the phytotron. One of the biggest obstacles to understanding ecosystem functions was the difficulty of studying what was occurring in the rhizosphere, the region of the soil surrounding the roots of plants, where microorganisms such as fungi and bacteria formed symbiotic relationships with plant roots. The close connections between fungi and roots, known as mycorrhizae, had been known since 1885, when the term “mycorrhiza” (or “fungus-root”) was coined, but understanding the details of this relationship took many decades. The fungus benefits by getting carbon, in the form of sugar, from the plant, while the plant obtains nutrients such as nitrogen and phosphorus from the fungus. Nellie Beetham Stark, collaborating with Frits Went in the 1960s, hypothesized that these associations were important for supporting tropical Amazonian forests that grew on poor soils. Their ideas stimulated more research on the ecological role of mycorrhizae, and this subject has grown into a large and vibrant field within ecology.
The use of radioactive isotopes was central to research on how plant roots and fungi exchanged nutrients, but scientists in the 1960s also came up with the idea of creating underground laboratories that became known as “rhizotrons” or “soil biotrons” for direct observation of the soil environment. One of the most elaborate was the Michigan Soil Biotron, which opened in 1987 at the University of Michigan’s Biological Station in northern Michigan. In the 1970s scientists also invented minirhizotrons, small buried observatories. Today these automated “soil ecosystem observatories” use technologies similar to those used for satellite and airborne remote sensing, but they observe changes at scales suited to soil processes.
Innovations in laboratory designs and instrumentation have been central to the advance of plant science since the emergence of the disciplines of plant physiology and ecology in the late-nineteenth century. Investments in complex laboratories as well as field-based instruments have helped make biology into Big Science, but such investments are still cheap compared to the cost of the instruments used by astronomers, particle physicists, and oceanographers. In the mid-twentieth century, scientists understood that this kind of investment was needed to meet the demands of the world’s fast-growing population. With the current climate crisis, it is important for the public to understand why continued investments in these areas of biological science should be priorities.
Sharon Kingsland is professor emerita in the Department of History of Science and Technology at Johns Hopkins University. She is the author of two previous books and has coedited two essay collections. She lives in Baltimore, MD.