History of the NCR-101
Committee on Controlled Environment
Technology and Use
W. Tibbitts, University of Wisconsin, Madison, WI
T. Krizek, Climate Stress Laboratory, USDA, Beltsville, MD
The NCR-101 Committee on Controlled Environment Technology and Use was organized in 1972 to provide guidance for research scientists on the proper operation and use of plant growth chambers.
The group was established because of the growing recognition that growth chambers, if used to their full potential, would greatly increase the precision in plant research and increase the understanding of the interacting factors controlling plant growth. Members had a common concern that there was a lack of guidelines on how to manage plants in growth chambers and how to monitor and control the environment to insure consistent and comparable results among laboratories.
In addition to the need for improved procedures for plant researchers, commercial growers, seedsmen and nurserymen were clamoring for guidance on the commercial use of controlled environments for seedling and nursery production. Many growth chambers were idle because of lack of adequate engineering expertise. Clearly, the time was ripe for professional societies to provide guidance on the proper operation and use of plant growth chambers.
The impetus for the organization of this NCR committee came from a group of horticulturists that had been meeting regularly for 3 years to develop guidelines on growth chamber use. They recognized the need to broaden involvement with other plant science disciplines and to obtain support for meeting on a regular basis. The NCR-101 committee was organized by two members from the North Central Region (Ted Tibbitts, University of Wisconsin & Allen Hammer, Purdue University), along with horticulturists from Cornell University, Pennsylvania State University, University of Arizona, North Carolina State University, and the University of California and a plant physiologist from USDA at Beltsville, MD. Although the organizing committee included primarily horticulturists, the initiation of the NCR-101 committee significantly broadened the scientific expertise. The first meeting at Purdue in the spring of 1972 also involved agronomists, agricultural engineers and plant pathologists from universities and USDA. The committee representation expanded over the years to include regular attendance by other government agencies including NASA and EPA and interested individuals from Guelph, Montreal, and New Brunswick in Canada. In addition industry representatives, particularly from growth chamber companies and lamp manufacturers, became regular attendees.
The annual meeting has commonly been held in March, with 1 1/2 days of business meeting and information exchange and 1/2 to 1 day for touring of controlled environment facilities. The meetings over the years have alternated between a visit to a location in the North Central region and a visit to a location outside of this region in the U.S. or Canada. The attendance over the years has been between 40 to 60 individuals.
Many different projects have been undertaken by this committee, which has led to a large number of refereed publications authored by different members of the committee. This included the following activities.
Publication of a growth chamber handbook
A major interest of the original ASHS committee was the publication of a manual of growth chamber procedures. This was organized and edited by R. Langhans and published in 1978 by Cornell University Press as: A Growth Chamber Manual: Environmental Control for Plants (Langhans, 1978). Over the years nearly 2000 copies of this manual have been distributed.
Within a short time after the book was published, members of the NCR-101 Committee recognized that information on controlled environments was increasing rapidly and that there was a need to update the original manual. Efforts to revise and expand the handbook were discussed repeatedly in the following years, but it was not until 1989, that a revision was initiated, again by R. Langhans, with the help of T. Tibbitts. The handbook was finally completed in 1996 and published in 1997 (Langhans and Tibbitts, 1997). [ordering info]
Development of standardized measurement and reporting guidelines
A long continuing effort has been the development of standardized measurement and reporting guidelines. This was initiated by the ASHS committee and has been regularly revised and updated by the NCR-101 committee. Individual members of the group assumed responsibility for submission of the guidelines to other professional societies; during this period they were published in many publications and newsletters (see e.g., Krizek, 1982; Krizek and McFarlane, 1983; Langhans and Tibbitts, 1981; McFarlane, 1981; Spomer, 1981a,b).
The universal acceptance of these guidelines was promoted through an International Controlled Environments Working Conference organized by T. Tibbitts and held at Madison in March 1979. This conference brought scientists and industry researchers together to discuss the development of effective guidelines for plant research. The proceedings of this conference were published by Academic Press (Tibbitts and Kozlowski, 1979).
The distribution of these guidelines has been helped significantly by the American Society of Agricultural Engineering (ASAE) in having them published as ASAE Engineering Practice EP 411.2 in their handbook of standards (ASAE, 1992). This effort was initiated by B. Curry (Ohio Agricultural Research and Development Center, Wooster) but carried through by J. Sager [National Aeronautics and Space Administration, Kennedy Space Center] and published first in 1982, with two subsequent revisions, the latest in 1992 (ASAE, 1992). The responsibility for updating these guidelines is being continued by the committee to the present by D. Krizek and supported by J. Sager and T. Tibbitts. The latest update of the guidelines has been included in Units, Symbols, and Terminology for Plant Physiology (Salisbury, 1996).
Development of quality assurance recommendations
Over the years, other guidelines and recommendations were prepared by the committee. Quality assurance recommendations were developed by J. Sager and T. Tibbitts to outline types of sensors to use, accuracy in sensors desired, frequency of measurement, and procedures for calibration of sensors. These were published in ASAE Engineering Practice EP 411.2 and in Biotronics in 1986 (NCR, 1986).
Development of a list of recommended instruments
The committee also extended the recommendations on instruments that could be used effectively in growth chambers by developing a list of types of instruments, along with a list of committee members willing to answer questions on instrument use. This list was distributed by members of the committee to interested persons and also distributed by headquarters staff at the American Society for Horticultural Science.
Throughout its history, the committee has directed significant effort toward the dissemination of information on improving the quality of growth chamber research through organization of regular workshops and frequent symposia at the annual ASHS meetings and brief reports published in HortScience.
Members of the committee have also worked to disseminate information worldwide through the development of sessions and workshops at International Horticultural Congresses held in Warsaw, Poland (1974), Sydney, Australia (1978), and Florence, Italy (1992) and through news notes in Phytotronics Newsletter, published in France until 1979, and in Biotronics, published in Japan since 1983.
Development of standardized cultural procedures
A major effort and interest of the original ASHS committee was in the development of standardized baseline growth curves of plants grown over 4 weeks. This effort was undertaken for two reasons: 1) to help scientists know if plants in their chambers were growing normally; and 2) to allow the committee to obtain agreement on growing and measurement procedures that could be recommended for general research use in controlled-environment chambers. There were large differences in opinion within the committee on growing media, watering procedures, nutrients to provide, where to take environmental measurements, importance of CO2 and humidity, need for ramping of light and temperature changes, etc.
Of importance to this baseline growth effort was obtaining and using a single large lot of growing medium (peat-vermiculite), obtaining a single lot of seed stored at one location, grading the seed for uniformity of size, providing each cooperator with the same kind of container (12.7-cm-diameter, 1-L, white plastic pots), standardizing the nutrient procedures by using the same nutrient solution (modified Hoagland), and use of an automatic watering system to insure that all plants were watered and fertilized at the same rate and frequency.
When there was agreement on the growing procedures with a solid medium in Aug. 1972, the members all agreed to undertake four or more uniformity studies in their individual growth chambers and forward the data to A. Hammer for statistical analysis and to summarize and prepare a manuscript for publication. Several individuals cooperated using lettuce, but only data from the four members who completed the requisite number of studies were included in the final manuscript (Hammer et al., 1978). This study documented rather conclusively the difficulty in obtaining precise repeatability in growth studies. It revealed that the variation in growth among studies was as large within the same laboratory as it was among separate laboratories.
A companion study was published on the elemental analysis of lettuce grown under baseline conditions in five separate controlled-environment facilities (Berry et al., 1981). This study documented the components of variation contributed by analytical method for individual elements, plant to plant variation, variation within a single laboratory and variation among different laboratories.
After the baseline growth studies with lettuce were completed, similar studies were initiated with marigold, and by the end of 1979, six committee members had completed four uniformity studies with marigold that were summarized and published (Ormrod et al., 1980).
These growth studies with lettuce and marigold revealed subtle differences in the composition of the peat-lite mixes from one lot to the next that made it difficult to totally standardize cultural procedures. W. Berry convinced the group that repeatability in growth required liquid culture, thus, followed a major effort toward development of a liquid culture system. The maintenance and time requirements for these liquid culture studies, however, proved too much for committee members, and insufficient data were collected to publish standardized growth data, although a research bulletin was prepared detailing the growing system (Tibbitts et al. 1978).
During the conduct of these baseline growth studies, committee members quickly recognized the very difficult task of defining and conducting repeatable growth studies. Small variations in any one environmental factor were found to have a large impact on the growth and yield of the plants. Thus, studies with additional species were abandoned when it was realized that standard growth curves might be less useful than committee members believed initially.
Development of a standardized instrument package
The development of standardized baseline growth curves required similar environmental measurements at the separate cooperating research laboratories. Thus, a proposal was developed by T. Tibbitts as principal investigator (with committee members as co-principal investigators) and submitted to the National Science Foundation (NSF) as a committee project to purchase a package of instruments that would be calibrated and distributed to the cooperating laboratories to be used in conjunction with baseline growth studies on selected horticultural crops. Initial funding of $10,000 for 2 years was received in 1972 and made possible the purchase of instruments for measuring and recording light, temperature, humidity, air movement, and provided tanks for standard CO2 concentration that were forwarded for use at each laboratory. Distributed with the standard instrument package were standardized procedures on where and how to make measurements to insure consistency among laboratories. NSF funding for these base-line growth studies was renewed in 1974 for 2 years at $29,500 and in 1976 for 2 more years at $41,500.
The value and usefulness of instruments that could be distributed to each laboratory to ensure similar measurements has continued to be recognized and promoted, particularly for radiation measurements – a project that has been continued to the present. The instruments were maintained by T. Tibbitts at the University of Wisconsin until 1997 and since that time by B. Bugbee at Utah State University. This effort is supported by a service charge (now $300) for each use at a location approved by the North Central Experiment Station directors. Upon receipt of the instrument package, each member is encouraged to contact other growth chamber users at his or her location and have them bring in their quantum sensor(s) or other radiation measuring instruments for cross comparison. Before and after each use, the radiation measuring instruments are audited with calibration systems maintained, originally at the University of Wisconsin and now, at Utah State University. Users are notified if any significant deviations have occurred in any instrument during the period it was distributed.
In the late 1970s to early 1980s, efforts were undertaken to have the National Bureau of Standards (NBS) [currently the National Institute of Standards and Technology (NIST)] calibrate some of the radiation sensors. Donald McSparron (NBS), T. Tibbitts, and D. Krizek conducted a cooperative study to examine the response of two LI-COR Inc. (Lincoln, Neb.) photon flux sensors for measuring photosynthetic photon flux under various spectral sources (Tibbitts et al., 1986). Because of difficulties in scheduling calibration at NBS, the calibration services have been maintained by the NCR committee.
Evaluation of long-wave radiation effects in growth chambers
In the course of the baseline growth studies, it was discovered that small differences in the amount of infrared radiation (IR) provided by the incandescent lamps had a significant effect on vegetative growth and nutrient composition of lettuce and marigold. Separate papers describing IR effects on growth and elemental concentration were published (Krizek and Berry, 1981; Krizek and Ormrod, 1980). Efforts to obtain NSF funding for a concerted committee study of the effects of spectral quality on plant growth under growth-chamber conditions proved unsuccessful. The committee has taken an active role in characterizing the large differences in thermal radiation (particularly 3- to 50-mm wavelengths) in various growth chambers and in documenting the significantly higher levels in certain chambers than present outdoors under solar radiation (Tibbitts et al., 1976).
Considerable emphasis has been placed on evaluating diverse types of long-wave monitoring devices that would be effective in characterizing this radiation. The sensors were made available to committee members through distribution with the instrument package. Initially, this included a Fritschen net radiometer. In the early 1990s, the committee purchased an Eppley pyranometer and an Eppley pyrgeometer to measure radiation in the region of 0.29 to 3 mm and 3 to 50 mm, respectively. The assistance of Henry Kostkowski at NBS in providing a Kendall radiometer as a calibration device and of Leo Fritschen (Univ. of Washington, Seattle) in providing a Fritschen net radiometer was invaluable in this effort.
Several committee members compared the spectral properties of various radiation sources using these sensors. Large differences in growth chamber design with regard to type and placement of the barrier separating the light bank and the plant growing area, cooling of the lamps in the light bank, and other design features among laboratories precluded the committee from publishing these data.
Concern over long-wave radiation and other spectral requirements of plants led to the organization by T. Tibbitts of a second International Controlled Environments Workshop at Madison, WI in Mar. 1994, with emphasis on lighting. Support was provided by NSF, NASA, DOE, growth chamber manufacturers, and lighting organizations. The proceedings were published by NASA (Tibbitts, 1995).
Cooperation with industry
The committee has encouraged participation by industry groups, with growth-chamber manufacturers and lamp manufacturers being regular attendees at the meetings. The committee has also played an active role in promoting the development of improved instrumentation for monitoring the environment and in the evaluation of new instrumentation that becomes available.
Early in the baseline growth studies, it became clear that variation in the amount of incandescent lighting among growth chambers was responsible for large differences in the far-red component of the spectrum among laboratories, but no broad-band sensors were available to monitor this variation. The committee was able to persuade LI-COR Inc. to manufacture a far-red sensor for inclusion in the instrument package that could be distributed to members.
Many members also recognized the need to carefully monitor the spectrum of radiation in their separate chambers, and the committee was able to obtain a spectroradiometer on loan from LI-COR Inc. that was available to members, and distributed with the instrument package, for two years.
In the late 1980s, Skye Instruments, (Liandrindod Wells, Powys, England) produced a model SKP-210 sensor to monitor photosynthetically active radiation (PAR) as yield photosynthetic flux (YPF). This instrument weights photons in the range from 360 to 760 nm according to plant photosynthetic response as opposed to the LI-COR quantum sensor, which weights all photons from 400 to 700 nm equally. Four members of the committee purchased the Skye YPF sensors and evaluated them under seven radiation sources [solar, INC, CWF, MH, HPS, LPS, and red light emitting diodes (LEDs)] with a LI-COR (model LI-1800) or an Optronics (model 740A) spectroradiometer during the ASHS meeting at Utah State University in 1991. This investigation led the committee to raise serious questions as to the accuracy of these special photosynthetic sensors.
Improved characterization of air movement
Accurate measurement of air velocity has been a major concern of the committee since its inception. Committee members found that when using a hot wire anemometer without analog output, at least ten measurements, at each of five uniformly spaced locations, were required to obtain an accurate determination of air movement. In 1991, a unidirectional instrument was purchased and distributed for use with the instrument package.
Cooperation with other American societies
Since its inception, the committee has maintained active liaison with many committees in other societies. One of the closest linkages has been with the ASAE through its Environment of Plant Structures Committee of the Structures and Environment Division (SE303) (known initially as the Plant and Animal Physiology Advisory Committee (ASAE C-18) and the American Society of Heating, Refrigerating and Air Conditioning Environment (ASHRAE) Committee on Plant Structures (known initially as ASHRAE TC 1.5 Committee and later as the ASHRAE TC 2 Committee). Members have provided input in updating the chapter on Environmental Control for Animals and Plants that are published in the ASHRAE Handbook of Fundamentals in 1967 (Chapter 9) and the ASHRAE Guide and Data Book, Applications in 1968 (Chapter 16).
The members provided input to the Fifth Edition of the Council of Biology Editors Style Manual and to the American Society of Plant Physiologists Instructions for Contributors (Krizek, 1983). The Committee also worked with the AIBS BioInstrumentation Advisory Committee (BIAC) headed by John Busser and participated in workshops sponsored by BIAC.
Some members of the committee have joined and taken an active role with the Commission Internationale de L’Eclairage (Commission on Illuminating Engineering) (CIE) in developing guidelines and standards for lighting of plants. T. Tibbitts and D. Krizek have been appointed chairman of CIE committees for this purpose. Measurement guidelines were published in 1993(Tibbitts, 1993)to standardize the use of photons over the 400-700 nm range as the guideline for plant photosynthetic lighting. Presently efforts are directed toward the development of general guidelines to cover the lighting requirements for plants in growth chambers and greenhouses. The committee has promoted interaction with the Commission for Horticultural Engineering of the International Society for Horticultural Science (ISHS) for the development of international workshops and symposia on controlled environment research. R. Langhans has served as the main contact with this group.
American Society of Agricultural Engineers. 1992. ASAE Engineering Practice ASAE EP 411.2. 1992. Guidelines for measuring and reporting environmental parameters for plant experiments in growth chambers, p. 505-508. In: R. H. Hahn (ed.). ASAE standards. Amer. Soc. Agr. Eng., St. Joseph, MI. HortScience 12:309-310.
Barnes, C., T. Tibbitts, J. Sager, G. Deitzer, D. Bubenheim, G. Roemer and B. Bugbee. 1993. Accuracy of quantum sensors measuring yield photon flux and photosynthetic flux. HortScience 28:1197-1200.
Berry, W.L., D.T. Krizek, D.P. Ormrod, J.C. McFarlane, R.W. Langhans and T.W. Tibbitts. 1981. Elemental control of lettuce grown under base-line conditions in five controlled-environment facilities. J. Amer. Soc. Hort. Sci. 106:661-666.
Hammer, P.A., T.W. Tibbitts, R.W. Langhans, and J.C. McFarlane. 1978. Base-line growth studies of Grand Rapids lettuce (Lactuca sativa L.) in controlled environments. J. Amer. Soc. Hort. Sci. 103:649-654.
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Tibbitts, T.W., D.A. McSparron, and D.T. Krizek. 1986. Spectral effects on the use of photon flux sensors for measurement of photosynthetic photon flux in controlled environments. Biotronics l5:3l-36.
Tibbitts, T.W., D.A. Palzkill, and H.M. Frank. 1978. Constructing a continuous circulation system for plant solution culture. Res. Bul. R2963. Res. Div. College of Agr. & Life Science, Univ. of Wisconsin, Madison.