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PubMedDate not supplied

Glycoalkaloids in potato tubers grown under controlled environments.

Tuber content of alpha-solanine, alpha-chaconine, and total glycoalkaloids (TGA) was determined for the potato cultivars, Norland, Russet Burbank, and Denali grown under different environmental conditions in growth chambers. The lowest TGA concentrations (0.30 to 0.35 mg g-1 dry tissue) were found in the cv. Norland with 400 micromoles m-2 s-1 photosynthetic photon flux (PPF), 12 h day length, 16 C temperature, and 350 micromoles mol-1 carbon dioxide. The ratio of alpha-chaconine to alpha-solanine was close to 60:40 under all growing conditions, except that it was 50:50 under the low temperature of 12 C. Cultivars responded similarly to environmental conditions although TGA was about 20% greater in cv. Russet Burbank and about 30% greater in Denali compared to Norland. The largest changes in TGA occurred with changes in temperature. In comparison to 16 C, TGA were 40% greater at 12 C, 80% greater at 20 C, and 125% greater at 24 C (0.70 mg g-1 dry weight). The TGA concentration increased from 10 to 25% with an increase in light from 400 to 800 micromoles m-2 s-1 PPF for all three cultivars. TGA increased 20% with extension of the day length from 12 to 24 hr and also increased 20% when carbon dioxide was increased from 350 to 1000 micromoles mol-1. TGA concentrations were not influenced by changes in relative humidity from 50 to 80%. TGA concentrations decreased only slightly in harvests made from 9 to 21 weeks after planting. Variations in TGA among the different growing conditions and cultivars were below 20 mg/100 g fresh weight (approximately 1.0 mg g-1 dry weight) recognized as the upper concentration for food safety. However the results suggest that TGA should be considered when potatoes are grown at temperatures above 20 C.

Alkaloids↗
PubMed2002

Flavonoid concentrations in three grass species and a sedge grown in the field and under controlled environment conditions in response to enhanced UV-B radiation.

An investigation was carried out to find whether enhanced levels of UV-B radiation induce increased concentrations of flavonoids in the leaves of the grass species Deschampsia antarctica, Deschampsia borealis and Calamagrostis epigeios and the sedge Carex arenaria. Whether the enhanced levels of UV-B influenced the proportions of the various flavonoids in the leaves was also studied. Increased flavonoid concentrations would improve the UV-B shielding of UV-B susceptible tissues. Using HPLC analysis the flavonoids orientin and luteolin were identified in D. antarctica, orientin in D. borealis and tricin in C. arenaria. Neither flavonoid concentrations nor the proportion of the various flavonoids in climate room grown D. antarctica and D. borealis plants differed between individuals grown under 0, ambient or elevated UV-B levels. After 12 weeks of growth biomass production and shoot-to-root ratios of D. antarctica were not affected by elevated UV-B radiation. Greenhouse grown C. epigeios plants contained higher concentrations and different proportions of flavonoids grown under elevated levels of UV-B than when grown under ambient or 0 UV-B. In C. epigeios plants grown in their natural habitat in the field under ambient or elevated levels of UV-B, flavonoid concentrations and proportions were the same in plants from both treatments. In the leaves of the sedge C. arenaria grown in a greenhouse flavonoid concentrations and proportions were not affected by UV-B radiation. Leaves were harvested four times during the growing season from C. arenaria plants grown in their natural habitat in the field under ambient or elevated levels of UV-B. Leaves harvested in January contained higher concentrations of flavonoids when grown under elevated UV-B than when grown under ambient UV-B radiation. In leaves harvested in May, September and December flavonoid concentrations were the same in plants grown under ambient or elevated UV-B. The proportion of the different flavonoids was the same for both treatments in all months. These results indicate that constitutive levels of flavonoids in these grass and sedge species are adequately high to protect them against ambient and elevated levels of solar UV-B radiation.

Environment, Controlled↗
PubMed2005

Partitioning respiration of C3-C4 mixed communities using the natural abundance 13C approach--testing assumptions in a controlled environment.

Contributions of C3 and C4 plants to respiration of C3-C4 ecosystems can be estimated on the basis of their contrasting 13C discrimination. But accurate partitioning requires accurate measurements of the isotope signature of whole system respiratory CO2 (deltaR), and of its members (delta3 and delta4). Unfortunately, experimental determination of representative delta3 and delta4 values is virtually impossible in nature, generating a need for proxies (surrogates) of delta3 and delta4 values (e.g., the delta of leaf biomass). However, recent evidence indicates that there may be systematic differences among the delta of respiratory and biomass components. Thus, partitioning may be biased depending on the proxy. We tested a wide range of biomass- and respiration-based delta proxies for the partitioning of respiration of mixed Lolium perenne (C3) - Paspalum dilatatum (C4) stands growing at two temperatures inside large 13CO2/ 12CO2 gas exchange chambers. Proxy-based partitioning was compared with results of reference methods, including (i) the delta of whole plant respiratory CO2 (delta3 and delta4) or (ii) respiration rate of intact C3 and C4 plants. Results of the reference methods agreed near perfectly. Conversely, some proxies yielded erroneous partitioning results. Partitioning based on either the delta of shoot or root respiratory CO2 produced the worst bias, because shoot respiratory CO2 was enriched in 13C by several per thousand and root respiratory CO2 was depleted by several per thousand relative to whole plant respiratory CO2. Use of whole plant or whole shoot biomass delta gave satisfactory partitioning results under the constant conditions of the experiments, but their use in natural settings is cautioned if environmental conditions are variable and the time scales of respiration partitioning differ strongly from the residence time of C in biomass. Other biomass-based proxies with faster turnover (e.g., leaf growth zones) may be more useful in changing conditions.

Carbon↗
PubMed2002

Heart rate variations in five-month-old children during interactions in a controlled environment.

UNLABELLED: This paper reports the first data of a study on heart rate variations of 13 5-mo-old infants seated in special chairs. Their electrocardiograms and behaviour were continuously recorded during sessions that were set up with their mother and a mother-child dyad that they met for the first time when the first session was organized. The protocol comprised two interaction phases between the infants and their mothers and two with one another. The same pairs of mother-child dyads were studied a second time 1 wk later. During the first session, the infants' heart rate variability increased significantly from the mother-infant interaction phases to the infant-infant interaction phases. During the second session, the variability was higher during the mother-infant phases than in the corresponding phases of the first session. This could be linked to changes in the mothers' behaviour and the infants' idea and excitement of meeting the child from the first session again. However, the variability was significantly lower during the infant-infant phases than during the mother-infant phases and the corresponding infant-infant phases of the first session. This corresponds to the development of affiliative behaviours in the infants. CONCLUSION: When two 5-mo-old infants were seated by their mothers in special chairs, significant differences were observed in their heart rate variability when they became familiar with each other, whether they were interacting with their mothers or with one another.

Analysis of Variance↗
PubMed2002

Interaction between drought and chronic high temperature during kernel filling in wheat in a controlled environment.

Wheat plants (Triticum aestivum L. 'Lyallpur'), limited to a single culm, were grown at day/night temperatures of either 18/13 degrees C (moderate temperature), or 27/22 degrees C (chronic high temperature) from the time of anthesis. Plants were either non-droughted or subjected to two post-anthesis water stresses by withholding water from plants grown in different volumes of potting mix. In selected plants the demand for assimilates by the ear was reduced by removal of all but the five central spikelets. In non-droughted plants, it was confirmed that shading following anthesis (source limitation) reduced kernel dry weight at maturity, with a compensating increase in the dry weight of the remaining kernels when the total number of kernels was reduced (small sink). Reducing kernel number did not alter the effect of high temperature following anthesis on the dry weight of the remaining kernels at maturity, but reducing the number of kernels did result in a greater dry weight of the remaining kernels of droughted plants. However, the relationship between the response to drought and kernel number was confounded by a reduction in the extent of water stress associated with kernel removal. Data on the effect of water stress on kernel dry weight at maturity of plants with either the full complement or reduced numbers of kernels, and subjected to low and high temperatures following anthesis, indicate that the effect of drought on kernel dry weight may be reduced, in both absolute and relative terms, rather than enhanced, at high temperature. It is suggested that where high temperature and drought occur concurrently after anthesis there may be a degree of drought escape associated with chronic high temperature due to the reduction in the duration of kernel filling, even though the rate of water use may be enhanced by high temperature.

Acclimatization↗
PubMed1997

A modified CROPGRO model for simulating soybean growth in controlled environments.

The CROPGRO crop growth model is adapted in order to analyze experimental data from a soybean (cv. Hoyt) experiment conducted at elevated CO2 levels (1200 micromol mol-1) at Kennedy Space Center, FL. The following adaptations to original CROPGRO produced model agreement with gas-exchange data: the input of square-wave temperature and photosynthetically active radiation (PAR) profiles; the input of the appropriate hydroponic substrate PAR albedo; modified biomass partitioning and developmental parameters; an increased leaf area expansion rate through the fifth vegetative node; a decreased specific leaf area after the fifth vegetative node; and an increased incident diffuse PAR fraction over typical field values. The model demonstrated here suggests that with continued development, modified CROPGRO will be a useful tool in the analysis and eventual optimization of legume production in bioregenerative life support systems.

Biomass↗
PubMed1998

Intracanopy lighting of cowpea canopies in controlled environments.

Traditional designs for plant-growth lighting in space life support systems irradiate tops of closed foliar canopies while canopy understories are light limited. "Intracanopy lighting," a technique whereby plants are allowed to grow up and around multiple layers of low-intensity lamps that irradiate interior portions of canopies, can potentially enhance productivity while reducing overall energy consumption. Intracanopy lighting of cowpea (Vigna unguiculata L. Walp) was optimized by varying stand densities and lining growth compartments with light-scattering or reflective films. Yield rates using intracanopy lighting were less than those obtained with traditional lighting strategies. However, yield efficiencies and energetic conversion efficiencies, parameters that put edible yield in terms of inedible biomass, energetic, spatial, and temporal penalties, indicate intracanopy lighting is more efficient in crop production. Single-leaf photosynthetic rates indicate all leaves participate in net carbon gain regardless of age and position within a canopy.

Biomass↗