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B Bugbee

Publications and source records attributed to B Bugbee.

At least 37 records · Page 2Linked to original sources
PubMed1996

Characterizing photosynthesis and transpiration of plant communities in controlled environments.

CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

Carbon Dioxide↗
PubMed1996

Mass transfer in the biological fast lane: high CO2 and a shallow root zone.

Elevated atmospheric CO2, which is common in regenerative systems, increases photosynthesis, plant growth, and root respiration, which increases the O2 demand in the root zone. Closed systems must make efficient use of volume and thus have shallow root zones. The root density and O2 demand in these artificial systems is 10 to 100 times higher than in field environments. Rapid hydroponic flow rates supply O2 to the root zone, but anaerobic microsites occur because of nonuniform flow rates. Our measurements suggest that, probably because of low O2 in such microsites, up to 30% of the nitrogen can volatilize from denitrification. We improved nitrogen recovery to about 85% by increasing the solution flow rate and reducing the nitrate concentration in solution to 100 micromoles.

Ammonia↗
PubMed1996

Phytotoxic effects of benzimidazole fungicides on bedding plants.

Benzimidazoles are effective and widely used fungicides, but they may be phytotoxic. We studied the effects of a single drench application of six benzimidazoles and one acetanilide fungicide on photosynthetic gas exchange, growth, development, and nutrient levels of four species of bedding plants in twenty growth-chamber and four greenhouse studies. Daily carbon gain and carbon-use efficiency were calculated from continuous crop gas-exchange measurements in the growth chambers. The maximum labeled rate of Benlate DF caused a 7- to 10-day decrease in net photosynthesis and daily carbon gain in transplants of all species. It also caused pronounced interveinal chlorosis and a 2- to 3-day delay in flowering. Growth of Benlate DF-treated plants was reduced more at high (90%) than at low (60% to 80%) relative humidity. Benlate DF had severe effects on 2-week-old petunia (Petunia xhybrida) seedlings in plug flats, reducing photosynthesis 25% to 57%. Cleary's 3336 WP decreased photosynthesis in some trials. Benlate DF reduced photosynthesis within 24 hours, but 3336 WP effects did not become apparent until 1 week after the treatment. This suggests different modes of inhibition. 3336 WP also caused leaf-tip and marginal chlorosis in impatiens (Impatiens wallerana). Mertect 340-F was extremely phytotoxic but is not labeled for drench applications (it was included because of its chemical similarity to other benzimidazoles). The only benzimidazole fungicide that did not reduce photosynthesis was Derosal, but it caused slight interveinal chlorosis in some studies with petunia. Benlate DF and Derosal decreased leaf Ca levels. Subdue (or metalaxyl), an acetanilide fungicide, did not affect photosynthesis or cause any visual symptoms. Our results indicate that some benzimidazole fungicides can cause growth reductions and visual damage in bedding plants.

Acetanilides↗
PubMed1995

The components of crop productivity: measuring and modeling plant metabolism.

Several investigators in the CELSS program have demonstrated that crop plants can be remarkably productive in optimal environments where plants are limited only by incident radiation. Radiation use efficiencies of 0.4 to 0.7 g biomass per mol of incident photons have been measured for crops in several laboratories. Some early published values for radiation use efficiency (1 g mol-1) were inflated due to the effect of side lighting. Sealed chambers are the basic research module for crop studies for space. Such chambers allow the measurement of radiation and CO2 fluxes, thus providing values for three determinants of plant growth: radiation absorption, photosynthetic efficiency (quantum yield), and respiration efficiency (carbon use efficiency). Continuous measurement of each of these parameters over the plant life cycle has provided a blueprint for daily growth rates, and is the basis for modeling crop productivity based on component metabolic processes. Much of what has been interpreted as low photosynthetic efficiency is really the result of reduced leaf expansion and poor radiation absorption. Measurements and models of short-term (minutes to hours) and long-term (days to weeks) plant metabolic rates have enormously improved our understanding of plant environment interactions in ground-based growth chambers and are critical to understanding plant responses to the space environment.

Biomass↗
PubMed1995

An approach to crop modeling with the energy cascade.

Use of plants in advanced life support requires models of crop growth to analyze data, to evaluate areas for improvement, and, for design and engineering, to predict the gas exchanges of crops. We used data from experiments at Utah State University and the Kennedy Space Center for wheat (Triticum aestivum L.) and examined it for time dependence of the major three components in the energy cascade: photosynthetic photon absorption, canopy quantum yield, and carbon use efficiency. From the Utah State data, we developed a model with a total of five trends: absorption increasing until canopy closure, then constant; quantum yield as constant, then decreasing during senescence; carbon use as constant. This system probably is the lower limit of simplicity to which a model can be reduced and yet provide substantial utility. We demonstrated this utility by using the model to predict photosynthesis and respiration for experiments at Kennedy Space Center. The most uncertainty arose in predicting a start time for the senescent decrease of canopy quantum yield. The model should be generally applicable to other crops grown in controlled environments, as a generic tool for the design of life support systems.

Biomass↗
PubMed1994

CO2 crop growth enhancement and toxicity in wheat and rice.

The effects of elevated CO2 on plant growth are reviewed and the implications for crop yields in regenerative systems are discussed. There is considerable theoretical and experimental evidence indicating that the beneficial effects of CO2 are saturated at about 0.12% CO2 in air. However, CO2 can easily rise above 1% of the total gas in a closed system, and we have thus studied continuous exposure to CO2 levels as high as 2%. Elevating CO2 from 340 to 1200 micromoles mol-1 can increase the seed yield of wheat and rice by 30 to 40%; unfortunately, further CO2 elevation to 2500 micromoles mol-1 (0.25%) has consistently reduced yield by 25% compared to plants grown at 1200 micromoles mol-1; fortunately, there was only an additional 10% decrease in yield as the CO2 level was further elevated to 2% (20,000 micromoles mol-1). Yield increases in both rice and wheat were primarily the result of increased number of heads per m2, with minor effects on seed number per head and seed size. Yield increases were greatest in the highest photosynthetic photon flux. We used photosynthetic gas exchange to analyze CO2 effects on radiation interception, canopy quantum yield, and canopy carbon use efficiency. We were surprised to find that radiation interception during early growth was not improved by elevated CO2. As expected, CO2 increased quantum yield, but there was also a small increase in carbon use efficiency. Super-optimal CO2 levels did not reduce vegetative growth, but decreased seed set and thus yield. The reduced seed set is not visually apparent until final yield is measured. The physiological mechanism underlying CO2 toxicity is not yet known, but elevated CO2 levels (0.1 to 1% CO2) increase ethylene synthesis in some plants and ethylene is a potent inhibitor of seed set in wheat.

Biomass↗
PubMed1994

The influence of elevated CO2 on non-structural carbohydrate distribution and fructan accumulation in wheat canopies.

We grew 2.4 m2 wheat canopies in a large growth chamber under high photosynthetic photon flux (1000 micromoles m-2 s-1) and using two CO2 concentrations, 360 and 1200 micromoles mol-1. Photosynthetically active radiation (400-700 nm) was attenuated slightly faster through canopies grown in 360 micromoles mol-1 than through canopies grown in 1200 micromoles mol-1, even though high-CO2 canopies attained larger leaf area indices. Tissue fractions were sampled from each 5-cm layer of the canopies. Leaf tissue sampled from the tops of canopies grown in 1200 micromoles mol-1 accumulated significantly more total non-structural carbohydrate, starch, fructan, sucrose, and glucose (p < 0.05) than for canopies grown in 360 micromoles mol-1. Non-structural carbohydrate did not significantly increase in the lower canopy layers of the elevated CO2 treatment. Elevated CO2 induced fructan synthesis in all leaf tissue fractions, but fructan formation was greatest in the uppermost leaf area. A moderate temperature reduction of 10 degrees C over 5 d increased starch, fructan and glucose levels in canopies grown in 1200 micromoles mol-1, but concentrations of sucrose and fructose decreased slightly or remained unchanged. Those results may correspond with the use of fructosyl-residues and release of glucose when sucrose is consumed in fructan synthesis.

Carbohydrate Metabolism↗
PubMed1993

Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux.

Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

Evaluation Studies as Topic↗
PubMed1992

Determining the potential productivity of food crops in controlled environments.

The quest to determine the maximum potential productivity of food crops is greatly benefitted by crop growth models. Many models have been developed to analyze and predict crop growth in the field, but it is difficult to predict biological responses to stress conditions. Crop growth models for the optimal environments of a Controlled Environment Life Support System (CELSS) can be highly predictive. This paper discusses the application of a crop growth model to CELSS; the model is used to evaluate factors limiting growth. The model separately evaluates the following four physiological processes: absorption of PPF by photosynthetic tissue, carbon fixation (photosynthesis), carbon use (respiration), and carbon partitioning (harvest index). These constituent processes determine potentially achievable productivity. An analysis of each process suggests that low harvest index is the factor most limiting to yield. PPF absorption by plant canopies and respiration efficiency are also of major importance. Research concerning productivity in a CELSS should emphasize: 1) the development of gas exchange techniques to continuously monitor plant growth rates and 2) environmental techniques to reduce plant height in communities.

Biomass↗
PubMed1992

Morphological responses of wheat to blue light.

Blue light significantly increased tillering in wheat (Triticum aestivum L.) plants grown at the same photosynthetic photon flux (PPF). Plants were grown under two levels of blue light (400-500 nm) in a controlled environment with continuous irradiation. Plants received either 50 micromoles m-2 s-1 of blue light or 2 micromoles m-2 s-1 blue light from filtered metal halide lamps at a total irradiance of 200 micromoles m-2 s-1 PPF (400-700 nm). Plants tillered an average of 25% more under the higher level of blue light. Blue light also caused a small, but consistent, increase in main culm development, measured as Haun stage. Leaf length was reduced by higher levels of blue light, while plant dry-mass was not significantly affected by blue light. Applying the principle of equivalent light action, the results suggest that tillering and leaf elongation are mediated by the blue-UV light receptor(s) because phytochrome photoequilibrium for each treatment were nearly identical.

Biomass↗
PubMed1992

Steady-state canopy gas exchange: system design and operation.

This paper describes the use of a commercial growth chamber for canopy photosynthesis, respiration, and transpiration measurements. The system was designed to measure transpiration via water vapor fluxes, and the importance of this measurement is discussed. Procedures for continuous measurement of root-zone respiration are described, and new data is presented to dispel myths about sources of water vapor interference in photosynthesis and in the measurement of CO2 by infrared gas analysis. Mitchell (1992) has described the fundamentals of various approaches to measuring photosynthesis. Because our system evolved from experience with other types of single-leaf and canopy gas-exchange systems, it is useful to review advantages and disadvantages of different systems as they apply to various research objectives.

Air↗
PubMed1992

Inherent limitations of nondestructive chlorophyll meters: a comparison of two types of meters.

Two types of nondestructive chlorophyll meters were compared with a standard, destructive chlorophyll measurement technique. The nondestructive chlorophyll meters were 1) a custom built, single-wavelength meter, and 2) the recently introduced, dual-wavelengh, chlorophyll meter from Minolta (model SPAD-502). Data from both meters were closely correlated with destructive measurements of chlorophyll (r2 = 0.90 and 0.93; respectively) for leaves with chlorophyll concentrations ranging from 100 to 600 mg m-2, but both meters consistently overestimated chlorophyll outside this range. Although the dual-wavelength meter was slightly more accurate than the single-wavelength meter (higher r2), the light-scattering properties of leaf cells and the nonhomogeneous distribution of chlorophyll in leaves appear to limit the ability of all meters to estimate in vivo chlorophyll concentration.

Chlorophyll↗
PubMed1991

Morphological responses of wheat to changes in phytochrome photoequilibrium.

Wheat plants (Triticum aestivum L.) were grown at the same photosynthetic photon flux (PPF), 200 micromoles per square meter per second, but with phytochrome photoequilibrium (phi) values of 0.81, 0.55, and 0.33. Plants grown at phi values of 0.55 and 0.33 tillered 43 and 56%, less compared with plants grown at phi of 0.81. Main culm development (Haun stage) was slightly more advanced at lower values of phi, and leaf sheaths, but not leaf lamina, were longer at lower phi. Dry-mass accumulation was not affected by different levels of phi. Three levels of PPF (100, 200, and 400 micromoles per square meter per second) and two lamp types, metal halide and high pressure sodium, were also tested. Higher levels of PPF resulted in more dry mass, more tillering, and a more advanced Haun stage. There was no difference in plant dry mass or development under metal halide versus high pressure sodium lamps, except for total leaf length, which was greater under high pressure sodium lamps (49.5 versus 44.9 centimeters, P < 0.01).

Agriculture↗
PubMed1988

Plant productivity in controlled environments.

To assess the cost and area/volume requirements of a farm in a space station or Lunar or Martian base, a few laboratories in the United States, the Soviet Union, France, and Japan are studying optimum controlled environments for the production of selected crops. Temperature, light, photoperiod, CO2, humidity, the root-zone environment, and cultivars are the primary factors being manipulated to increase yields and harvest index. Our best wheat yields on a time basis (24 g m-2 day-1 of edible biomass) are five times good field yields and twice the world record. Similar yields have been obtained in other laboratories with potatoes and lettuce; soybeans are also promising. These figures suggest that approximately 30 m2 under continuous production could support an astronaut with sufficient protein and about 2800 kcal day-1. Scientists under Iosif Gitelzon in Krasnoyarsk, Siberia, have lived in a closed system for up to 5 months, producing 80% of their own food. Thirty square meters for crops were allotted to each of the two men taking part in the experiment. A functional controlled-environment life-support system (CELSS) will require the refined application of several disciplines: controlled-environment agriculture, food preparation, waste disposal, and control-systems technology, to list only the broadest categories. It has seemed intuitively evident that ways could be found to prepare food, regenerate plant nutrients from wastes, and even control and integrate several subsystems of a CELSS. But could sufficient food be produced in the limited areas and with the limited energy that might be available? Clearly, detailed studies of food production were necessary.

Biomass↗
PubMed1988

Radiation in controlled environments: influence of lamp type and filter material.

Radiation in controlled environments was characterized using fluorescent and various high-intensity-discharge (HID) lamps, including metal halide, low-pressure sodium, and high-pressure sodium as the radiation source. The effects of water, glass, or Plexiglas filters on radiation were determined. Photosynthetic photon flux (PPF, 400 to 700 nm), spectra (400 to 1000 nm), shortwave radiation (285-2800 nm), and total radiation (300 to 100,000 nm) were measured, and photosynthetically active radiation (PAR, 400 to 700 nm) and longwave radiation (2800 to 100,000 nm) were calculated. Measurement of PPF alone was not an adequate characterization of the radiation environment. Total radiant flux varied among lamp types at equal PPF. HID lamps provided a lower percentage of longwave radiation than fluorescent lamps, but, when HID lamps provided PPF levels greater than that possible with fluorescent lamps, the amount of longwave radiation was high. Water was the most effective longwave radiation filter. Glass and Plexiglas similarly filtered longwave more than shortwave radiation, but transmission of nonphotosynthetic shortwave radiation was less with Plexiglas than glass. The filter materials tested would not be expected to influence photomorphogenesis because radiation in the action spectrum of phytochrome was not altered, but this may not be the only pigment involved.

Environment, Controlled↗
PubMed1987

Wheat production in controlled environments.

Our goal is to optimize conditions for maximum yield and quality of wheat to be used in a controlled-environment, life-support system (CELSS) in a Lunar or Martian base or perhaps in a space craft. With yields of 23 to 57 g m-2 d-1 of edible biomass, a minimum size for a CELSS would be between 12 and 30 m2 per person, utilizing about 600 W m-2 of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon-dioxide levels, humidity, and wind velocity are controlled in state-of-the-art growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants per meter2. Densities up to 2000 plants m-2 appear to increase seed yield. Biomass production increases almost linearly with increasing irradiance from 400 to 1700 micromoles m-2 s-1 of photosynthetic photon flux (PPF), but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization. High temperatures (25 to 27 degrees C) and long days shorten the life cycle and promote rapid growth, but cooler temperatures (20 degrees C) and shorter days greatly increase seed number per head and thus yield (g m-2). The life cycle is lengthened in these conditions but yield per day (g m-2 d-1) is still increased. We have evaluated about 600 cultivars from around the world and have developed several breeding lines for our controlled conditions. Some of our ultra-dwarf lines (30 to 50 cm tall) look especially promising with high yields and high harvest indices (percent edible biomass).

Biomass↗
PubMed1984

Tomato growth as affected by root-zone temperature and the addition of gibberellic acid and kinetin to nutrient solutions.

The effect of root-zone temperature on young tomato plants (Lycopersicon esculentum Mill. cv. Heinz 1350) was evaluated in controlled environments using a recirculating solution culture system. Growth rates were measured at root-zone temperatures of 15 degrees, 20 degrees, 25 degrees, and 30 degrees C in a near optimum foliar environment. Optimum growth occurred at 25 degrees to 30 degrees during the first 4 weeks of growth and 20 degrees to 25 degrees during the 5th and 6th weeks. Growth was severely restricted at 15 degrees. Four concentrations of gibberellic acid (GA3) and kinetin were added to the nutrient solution in a separate trial; root-zone temperature was maintained at 15 degrees and 25 degrees. Addition of 15 micromoles GA3 to solutions increased specific leaf area, total leaf area, and dry weight production of plants in both temperature treatments. GA3-induced growth stimulation was greater at 15 degrees than at 25 degrees. GA3 may promote growth by increasing leaf area, enhancing photosynthesis per unit leaf area, or both. Kinetic was not useful in promoting growth at either temperature.

Adenine↗