Plants and environment: Two decades of research at the Canberra phytotron

The research carried out at the Canberra phytotron, CERES, during the first twenty years of its operation is reviewed as a case study of the opportunities, problems and value of phytotron research. The climatic responses of a large number of species, both wild and domesticated, are examined as well as those of fungal and viral pathogens and rhizobial symbionts. Some aspects of the design of CERES are briefly considered, and a few aspects of the variation between plants in climatic response, with the C₄ photosynthetic syndrome taken as a case history of the linkages between biochemistry, anatomy and response to climate. Research in ecology, forestry, horticulture, plant pathology, rhizobial microbiology, anatomy and ultrastructure—and specific aspects of biochemistry, plant nutrition and genetics—are reviewed to indicate the range of botanical disciplines which can profit from access to a phytotron. The ecological research at CERES, much of it with trees and perennial grasses, particularly highlights the value of combining field and phytotron studies. Work on seed proteins, hybrid vigor and plant growth regulators is also reviewed. The next part of the paper considers the effects of the major environmental factors, temperature, daylength, irradiance, atmospheric CO₂ level and water stress, together with their interactions and the problems of correlating phytotron and field responses. The effect of these factors on the various processes of growth and development are considered, and the stages of development most sensitive to them. An evolutionary perspective on yield potential is then discussed, leading to a consideration of photosynthesis, translocation, partitioning and storage organ growth as yield-determining processes. The final part considers the uses of phytotrons in agricultural, horticultural and forestry research, in terms of examples from work at CERES on the manipulation of breeding systems, the clarification of plant breeding objectives, the use of phytotron conditions for selection, the prediction of adaptation and spread, and models for yield prediction and pest management. Several areas requiring more attention are identified, and some conclusions are drawn on the value of access to a phytotron such as CERES for botanical research of many kinds.     

Short photoperiod induces dormancy in Lotus (Nelumbo nucifera)

BACKGROUND AND AIMS: Lotus (Nelumbo nucifera) has been cultivated as an ornamental and food plant in Japan for more than 1000 years. As large areas are required for its cultivation (approximately 2 m2 per plant), physiological research, such as into the effect of environmental factors on dormancy, has not been well studied until recently. In this paper, seedlings were used to examine environmental factors affecting dormancy induction. METHODS: In a first experiment, seeds were sown from 6 April to 6 October at 2-month intervals, and cultivated for 2 months in an unheated greenhouse. In a second experiment, seeds were prepared for germination on 16 November and 16 May and the seedlings were grown at 25 or 30 degrees C under natural daylength in phytotron growth rooms. After 1 month, the seedlings were cultivated at 20, 25 or 30 degrees C for a further month. The number of leaves and rhizome branches on the main stem were counted, and growth of rhizomes on the main stem was calculated using a rhizome enlargement index (= maximum internode diameter/internode length) after 2 months of culture in both experiments. KEY RESULTS: Rhizomes elongated without enlargement when the seeds were sown in April and June. Sowing the seeds in August and October resulted in rhizome enlargement from the tenth and fifth internodes, respectively. Rhizomes enlarged in the November-sowing but elongated in the May-sowing irrespective of temperature treatments under natural daylength in the phytotron rooms. The seedlings cultivated from May at 25-30 degrees C for 2 months had more leaves, and more rhizome branches and nodes than those cultivated from November. CONCLUSIONS: Short days led to induced dormancy in lotus.     

Controlled-Environment Sunlit Plant Growth Chambers

Controlled environment sunlit plant growth chambers have been built because of a great interest in plant responses to environmental variables under light intensities approaching those of natural sunlight conditions. Individual research projects have designed sunlit chambers that differ in size, structure, material, and environmental control systems dependent on the goals of the projects. Most literature describes plant organism responses to environmental variables, whereas reports of system design and performance are few. The objective of this article is to present a review of the engineering aspects of the design, environmental control, and performance of sunlit growth chambers that have been described in the literature. Most controlled environment sunlit growth chambers have been constructed with experimental plants grown in either pots or soil bins. Although a few sunlit growth chambers were designed for field grown plants, precise environmental control was not available. Further progress in the development of precise controlled environment sunlit growth chambers should include portability (or movability) so these chambers can be used in multiple field sites for greater cost-effectiveness. Modifications for improvements in guidelines for the design and operation of controlled environment growth chamber studies are also proposed.     

Neighbour identity modifies effects of elevated temperature on plant performance in the High Arctic

Competition among plants in extreme environments such as the High Arctic has often been described as unimportant, or even nonexistent; environmental factors are thought to overrule any negative plant–plant interactions. However, few studies have actually addressed this question experimentally in the Arctic, and those that did found only little evidence for competition. Such species interactions will presumably become more important in the future, as Global Climate Change takes effect on terrestrial ecosystems. We investigated plant–plant interactions in the High Arctic, following the growth of Luzula confusa and Salix polaris in pure and mixed stands, and under elevated‐temperature treatment over 2 years. To understand the mechanisms of competition, a parallel experiment was undertaken in phytotrons, manipulating competition, temperature and nutrient availability. Our findings indicate that competition is acting in the natural vegetation, and that climatic warming will alter the balance of interactions in favour of the dwarf shrub S. polaris. The phytotron experiment suggested that the mechanism is a higher responsiveness of Salix to nutrient availability, which increased under warming in the field. While Luzula showed a positive response to higher temperature in the lab, its performance in mixed stands in the field was actually reduced by warming, indicating a competitive repression of growth by Salix. The growth of Salix was also reduced by the presence of Luzula, but it was still able to profit from warming. Our findings suggest that climatic warming will result in greater shrub dominance of High Arctic tundra, but we also conjecture that grazing could reverse the situation to a graminoid‐dominated tundra. These two divergent scenarios would have different implications for ecosystem feedbacks to climatic change.     

Design and Construction of an Inexpensive Homemade Plant Growth Chamber

Plant growth chambers produce controlled environments, which are crucial in making reproducible observations in experimental plant biology research. Commercial plant growth chambers can provide precise controls of environmental parameters, such as temperature, humidity, and light cycle, and the capability via complex programming to regulate these environmental parameters. But they are expensive. The high cost of maintaining a controlled growth environment is often a limiting factor when determining experiment size and feasibility. To overcome the limitation of commercial growth chambers, we designed and constructed an inexpensive plant growth chamber with consumer products for a material cost of $2,300. For a comparable growth space, a commercial plant growth chamber could cost $40,000 or more. Our plant growth chamber had outside dimensions of 1.5 m (W) x 1.8 m (D) x 2 m (H), providing a total growth area of 4.5 m² with 40-cm high clearance. The dimensions of the growth area and height can be flexibly changed. Fluorescent lights with large reflectors provided a relatively spatially uniform photosynthetically active radiation intensity of 140–250 μmoles/m²/sec. A portable air conditioner provided an ample cooling capacity, and a cooling water mister acted as a powerful humidifier. Temperature, relative humidity, and light cycle inside the chamber were controlled via a z-wave home automation system, which allowed the environmental parameters to be monitored and programmed through the internet. In our setting, the temperature was tightly controlled: 22.2°C±0.8°C. The one-hour average relative humidity was maintained at 75%±7% with short spikes up to ±15%. Using the interaction between Arabidopsis and one of its bacterial pathogens as a test experimental system, we demonstrate that experimental results produced in our chamber were highly comparable to those obtained in a commercial growth chamber. In summary, our design of an inexpensive plant growth chamber will tremendously increase research opportunities in experimental plant biology.     

Influence of 50 Hz electromagnetic fields on recurrent embryogenesis and germination of cork oak somatic embryos

Plant tissue culture techniques are carried out under environmentally controlled conditions in phytotrons. However, electric components of phytotrons generate electromagnetic fields that may act as a environmental factor influencing plant growth and morphogenesis. Isolated somatic embryos of Quercus suber, picked from embryogenic lines, were chronically exposed to a 50 Hz and 15 μT electromagnetic field generated in a Helmholtz-coil system for 8 weeks, in order to examine if the extremely low frequency (ELF) magnetic field (MF) affected the morphogenic behaviour of embryogenic cultures during recurrent embryogenesis. Germination of somatic embryos from genotype G7.1 was carried out under the same electromagnetic field, and also under conditions in which the local geomagnetic field was suppressed. The ELF MF did not influence the growth of embryogenic clumps of the assayed genotypes, but reduced the number of detachable embryos produced by genotype G3.27. The ELF MF did not modify the percentages of germination or plant formation of somatic embryos. However, somatic embryos had better germination when cultured under the suppressed geomagnetic field condition. This revised version was published online in June 2006 with corrections to the Cover Date.     

High temperatures limit plant growth but hasten flowering in root chicory (Cichorium intybus) independently of vernalisation

An increase in mean and extreme summer temperatures is expected as a consequence of climate changes and this might have an impact on plant development in numerous species. Root chicory (Cichorium intybus L.) is a major crop in northern Europe, and it is cultivated as a source of inulin. This polysaccharide is stored in the tap root during the first growing season when the plant grows as a leafy rosette, whereas bolting and flowering occur in the second year after winter vernalisation. The impact of heat stress on plant phenology, water status, photosynthesis-related parameters, and inulin content was studied in the field and under controlled phytotron conditions. In the field, plants of the Crescendo cultivar were cultivated under a closed plastic-panelled greenhouse to investigate heat-stress conditions, while the control plants were shielded with a similar, but open, structure. In the phytotrons, the Crescendo and Fredonia cultivars were exposed to high temperatures (35 °C day/28 °C night) and compared to control conditions (17 °C) over 10 weeks. In the field, heat reduced the root weight, the inulin content of the root and its degree of polymerisation in non-bolting plants. Flowering was observed in 12% of the heat stressed plants during the first growing season in the field. In the phytotron, the heat stress increased the total number of leaves per plant, but reduced the mean leaf area. Photosynthesis efficiency was increased in these plants, whereas osmotic potential was decreased. High temperature was also found to induced flowering of up to 50% of these plants, especially for the Fredonia cultivar. In conclusion, high temperatures induced a reduction in the growth of root chicory, although photosynthesis is not affected. Flowering was also induced, which indicates that high temperatures can partly substitute for the vernalisation requirement for the flowering of root chicory.     

An improved,simple, hydroponic method for growing<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Arabidopsis thaliana is one os the most studied plant model systems. Completing the genomic sequence ofA. thaliana has provided new opportunities for physiological and biochemical studies. While its small size is advantageous for genetic studies, the plant's low biomass makes it difficult to obtain enough plant material for biochemical and physiological research. The small size and rosette leaf structure, combined with the sensitivity of the apical meristem to flooding, make hydroponic growth of this model plant difficult. A few systems for hydroponic culture ofArabidopsis have been described. Gibeaut et al. (1997) introduced the use of rockwool forArabidopsis hydroponic culture. We have improved this system by introducing small-volume plastic containers with improved plugs to support the rockwool. This method is simpler than the original setup and provides improved germination and growth. The smaller containers enable the use of this system in growth chambers or small growth rooms for a large number of parallel experiments.     

Relative growth and nutrient accumulation rates for tobacco

Summary Tobacco plants (Nicotiana tabacum L.) were grown from transplanting until floral expression in the phytotron units of Southeastern Plant Environment Laboratories to evaluate the relationship between relative growth rate (RGR) and relative accumulation rates (RAR) of N, P, K, Ca, and Mg. RAR is calculated to be analogous to RGR. Plants were grown in both controlled-environment rooms with artificial light and air-conditioned greenhouses with natural light at three temperature conditions and three application rates of N-P-K. RGR and RAR were calculated only for the period of grand growth which occurred within the interval from 7 to 32 days after transplanting. In general, neither RGR nor RAR were affected by temperature or nutrient level. However, both temperature and nutrient level affected dry matter accumulation of the plants apparently by an influence on the rapidity with which plants adjusted to their new environment during the initial 7-day interval after transplanting. RAR for P and K were coequal with RGR of the whole plant; thus, the concentrations of P and K within the plant tended to remain constant during growth. RAR for N, Ca, and Mg were less than RGR for the whole plant; thus, internal concentrations of these nutrients declined during growth. RAR of N, Ca, and Mg for the whole plant were equivalent to RGR of the roots. As a rationale for the association of RGR of roots and RAR of N, it is proposed that the soluble carbohydrate pool in the roots concurrently influences both N absorption, as NO₃ ^-, and growth of new roots of immature plants. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC.     

A laboratory technique for examining the flight activity of insects under controlled environment conditions

A technique was developed for studying the flight activity of the, black fly,Simulium arcticum, under controlled environment conditions. Wind speed, light, temperature and humidity could be controlled and monitored in the flight chambers. Accurate measurement and recording of individual insect activity were achieved with a high-sensitivity video recording and monitoring system. The controlled-environment monitoring system is adaptable for investigations of the environmental behaviour and physiology of various insect species.     

Raising the Maximum Permissible Air Velocity in Controlled Environment Plant Growth Chambers

Phaseolus vulgaris L. plants were grown in two naturally lighted, outdoor controlled environment plant growth chambers. The approach velocity to the plant growing zone was 75 cm s^?1 in one chamber and 225 cm s^?1 in the other. The lower air velocity represents the presently considered maximum permissible air velocity in controlled environment plant growth chambers. The humidity in both chambers was near saturation. After three weeks' growth in these chambers, there were no significant differences in fresh or dry weights of the plants or any parts thereof. The high air velocity reduced the transpiration rate as predicted by energy budget considerations and significantly lowered the average leaf temperature of the crop by three degrees. The data strongly support the hypothesis that the maximum permissible air velocity in controlled environment plant growth chambers can be raised considerably if the humidity is maintained high.     

植物对开放式CO2 浓度增高(FACE)的响应与适应研究进展

开放式CO2浓度增高(FACE)系统是近年研究植物对高CO2浓度响应和适应的新手段,它比以往密闭和半密闭系统对实验植物生长环境的干扰少.利用FACE系统进行研究更有助于正确地预测未来大气CO2浓度增高对植物的影响.该文结合作者的研究工作简要评介了FACE系统与以往密闭和半密闭式CO2浓度增高实验系统的不同之处以及近年来利用FACE系统所作的最新研究进展.     

Growth Response of a Chrysanthemum Crop to the Environment. I. Experimental Techniques

The construction and mode of operation of six daylit assimilationchambers and the methods used to measure canopy photosynthesisand radiation interception are described. The chambers havea cuboid plant space, with sides 1.2 m long, in which temperaturecan be controlled from ambient to 30 °C with a temporalvariation of ±0.5 °C. Conductimetric controllersmaintain CO₂ concentration in the chambers within ±5per cent of the desired values. The amount of CO₂ injected andother variables needed to relate mean CO₂ assimilation ratesto mean radiation flux density over successive 10 min intervalsthroughout the day are recorded on punched tape for subsequentcomputer processing. The chambers have limitations in the number,range and variability of the environmental factors controlledbut they cost approximately one tenth as much as commercialdaylit cabinets and provide adequate, reproducible data formodelling many aspects of crop growth.     

Effects of carbon dioxide concentration on the interactive effects of temperature and water vapour on stomatal conductance in soybean

Soybeans were grown at three CO₂ concentrations in outdoor growth chambers and at two concentrations in controlled-environment growth chambers to investigate the interactive effects of CO₂, temperature and leaf-to-air vapour pressure difference (LAVPD) on stomatal conductance. The decline in stomatal conductance with CO₂ was a function of both leaf temperature and LAVPD. In the field measurements, stomatal conductance was more sensitive to LAVPD at low CO₂ at 30 °C but not at 35 °C. There was also a direct increase in conductance with temperature, which was greater at the two elevated carbon dioxide concentrations. Environmental growth chamber results showed that the relative stomatal sensitivity to LAVPD decreased with both leaf temperature and CO₂. Measurements in the environmental growth chamber were also performed at the opposing CO₂, and these experiments indicate that the stomatal sensitivity to LAVPD was determined more by growth CO₂ than by measurement CO₂. Two models that describe stomatal responses to LAVPD were compared with the outdoor data to evaluate whether these models described adequately the interactive effects of CO₂, LAVPD and temperature.     

Influence of Environmental Factors and Age of Plant on the Control of Bermudagrass by Glyphosate

The influence of environmental factors and age of plant on the control of bermudagrass was studied in the phytotron. The results showed that glyphosate gave better control on bermudagrass under high light intensity and high soil hmnidity than under low light intensity and low soil humidity. During the first two weeks the efficiency of glyphosate treatment differed markedly; however, the difference between these different conditions deminished with the increase in concentration or with prolonged treatment. The environmental factors and concentration of glyphosate also exerted a significant influence on the resumption of the plant growth thereafter. The lower the light intensity the less was the potential capacity for resumption of the growth. In our experiments there was no resumption of growth after the treatment with glyphosate at a concentration of 0.4%. The response of bermudagrass at different ages to glyphosate was significantly different. The older the plant the higher was the percentage of the survival and the resumption of the plant growth.     

Growth responses, biomass partitioning, and nitrogen isotopes of prairie legumes in response to elevated temperature and varying nitrogen source in a growth chamber experiment

? Premise of the Study: Because legumes can add nitrogen (N) to ecosystems through symbiotic fixation, they play important roles in many plant communities, such as prairies and grasslands. However, very little research has examined the effect of projected climate change on legume growth and function. Our goal was to study the effects of temperature on growth, nodulation, and N chemistry of prairie legumes and determine whether these effects are mediated by source of N. ? Methods: We grew seedlings of Amorpha canescens, Dalea purpurea, Lespedeza capitata, and Lupinus perennis at 25/20°C (day/night) or 28/23°C with and without rhizobia and mineral N in controlled-environment growth chambers. Biomass, leaf area, nodule number and mass, and shoot N concentration and δ(15)N values were measured after 12 wk of growth. ? Key Results: Both temperature and N-source affected responses in a species-specific manner. Lespedeza showed increased growth and higher shoot N content at 28°C. Lupinus showed decreases in nodulation and lower shoot N concentration at 28°C. The effect of temperature on shoot N concentration occurred only in individuals whose sole N source was N(2)-fixation, but there was no effect of temperature on δ(15)N values in these plants. ? Conclusions: Elevated temperature enhanced seedling growth of some species, while inhibiting nodulation in another. Temperature-induced shifts in legume composition or nitrogen dynamics may be another potential mechanism through which climate change affects unmanaged ecosystems.     

Plant Response to Integrated Impact of Natural and Anthropogenic Stress Factors

Responses of cultivated plants (Lepidium sativum L. and Lycopersicon esculentum Mill.), i.e., changes in growth characteristics, pigment and proline content, to an integrated impact of natural (temperature) and anthropogenic (substrate acidity, population density, and heavy metals) stress factors were studied under controlled environmental conditions. The experiments were carried out in a phytotron (tomato) and under laboratory conditions (garden cress). The external stress factors produced a general suppression of growth and pigment synthesis and differentially affected individual biological characteristics of the plants. Each of the stress factors narrowed the interval of plant tolerance to other stress factors. Strong impact of one stress factor affected plant homeostasis mechanisms by weakening plant response to other stress factors.     

The Structure of the Two Ecological Paradigms

Ecological theory is built upon assumptions about the fundamental nature of organism-environment interactions. We argue that two mutually exclusive sets of such assumptions are available and that they have given rise to alternative approaches to studying ecology. The fundamentally different premises of these approaches render them irreconcilable with one another. In this paper, we present the first logical formalisation of these two paradigms.The more widely-accepted approach - which we label the demographic paradigm - includes both population ecology and community ecology (synecology). Demographic ecology assumes that the environment is relatively stable and that biotic processes, governed predominantly by resource availability, are the most important of ecological and evolutionary influences. Moreover, ecological processes are assumed to translate into directional selection pressures that drive significant evolutionary change on a local scale through the process of optimisation.Serious deficiencies in aspects of the demographic approach have been identified over the past few decades by various ecologists, including Gleason, Andrewartha and Birch, White, Den Boer, Strong, Simberloff, and others. Short-term evolutionary optimisation has also been seriously questioned.The development of the alternative approach (autecology) has been subverted by the prominence of demographic ecology. Moreover, it has not been recognised that autecology is underpinned by robust principles and that they are independent of the underlying demographic principles. Components of the autecological approach have been developed to some extent, but they have not been integrated with ancillary fields of study. We therefore articulate the assumptions from which autecology is derived, and use this as a basis for integrating the various spheres of autecological research.We add to the ongoing development of autecology by linking autecological understanding, in so far as it is developed, with the evolutionary justification for species' characteristics being stable in an environment that is continuously dynamic in space and time. The ecology of organisms is essentially an ongoing matching of their species-specific characteristics to the prevailing environmental factors and dynamics. We thus provide a consistent logic through the following subject areas; climate and climate change, spatial and temporal environmental heterogeneity and dynamic theory, physiology, behaviour, migration, and evolution. We demonstrate why adaptation cannot be an ongoing process, but takes place only when organisms are prevented, by incidental influences, from matching the overall dynamics of the environment.     

Application of vaccines and dietary supplements in aquaculture: possibilities and challenges

The development of vaccines has proven essential for the development of a successful finfish aquaculture industry by preventing the occurrence of diseases like furunculosis and vibriosis in industrialised finfish farming. Further developments, like DNA vaccines, will aid in controlling even more diseases in the future. There are however many diseases where it is difficult to produce effective vaccines. Furthermore, many disease outbreaks may occur due to impaired animal welfare. Identifying factors associated with disease and optimizing health and welfare through biotechnological developments is likely to be an important research area in the future. The fact that dietary manipulation can affect fish gut microbiota thus improving disease resistance is well known from mammalian science, and is slowly gaining ground in finfish research. Both prebiotic and probiotic approaches have been used in fish, with particular focus on lactic acid bacteria. Positive effects include enhanced growth and feed efficiency, improved immunity and disease resistance. The synbiotic concept (using a combination of probiotics and prebiotics) is particularly promising and is gaining increased interest within the research community. Immunostimulants may also improve disease resistence via increase humoral and cellular immune responses. The most promising immunostimulants at present are β-glucans, alginate and Ergosan. Additionally, medical plant extracts and their products are receiving increased attention as immune modulators, but further studies are needed. There are also great expectations or the future usage of microalgae to control microbiota and optimize fish health.