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PubMed1979

Kinetics and time dependence of the effect of far red light on the photoperiodic induction of flowering in wintex barley.

Flowering in the long day plant Hordeum vulgare L. var. Wintex barley was enhanced by the addition of far red light to the main light portion of the photoperiod. Far red energy was provided to produce quantum flux ratios (660/730 nm) and phytochrome photoequilibria (Pfr/total phytochrome) equivalent to those reported both beneath a leaf canopy and outside a canopy at twilight. The photoperiodic requirement for long days can be completely eliminated by the addition of far red light. However, both the effect of extending the photoperiod without far red and the addition of far red to 12-hour photoperiods were suboptimal. Maximal stimulation was achieved only when far red was added to continuous light. The duration of the period of maximal apex elongation rate, as well as the reduction of the time required for floral initiation, were saturated by three inductive cycles. When far red energy was provided intermittently during 3 days of continuous light, the ability to respond varied in a circadian manner. This enhancement of flowering by far red appears to be mediated by the "high irradiance response" of phytochrome.

Journal Article↗

PubMed1982

Efficiency of Nitrogen Assimilation by N(2)-Fixing and Nitrate-Grown Soybean Plants (Glycine max [L.] Merr.).

Nodulated and non-nodulated (not inoculated) soybeans (Glycine max [L.] Merr. cv Wells) were grown in controlled environments with N(2) or nonlimiting levels of NO(3) (-), respectively, serving as sole source of nitrogen. The efficiency of the N(2)-fixing plants was compared with that of the nitrate-supplied plants on the basis of both plant age and plant size. Efficiency evaluations of the plants were expressed as the ratio of moles of carbon respired by the whole plant to the moles of nitrogen incorporated into plant material.Continuous 24-hour CO(2) exchange measurements on shoot and root systems made at the beginning of flowering (28 days after planting) indicated that N(2)-fixing plants respired 8.28 moles of carbon per mole of N, fixed from dinitrogen, while nitrate-supplied plants respired only 4.99 moles of carbon per mole of nitrate reduced. Twenty-one-day-old nitrate-supplied plants were even more efficient, respiring only 3.18 moles of carbon per mole of nitrate reduced. The decreased efficiency of the N(2)-fixing plants was not due to plant size since, on a dry weight basis, the 28-day-old N(2)-fixing plants were intermediate between the 28- and 21-day-old nitrate-supplied plants.The calculated efficiencies were predominantly a reflection of root-system respiration. N(2)-fixing plants lost 25% of their daily net photosynthetic input of carbon through root-system respiration, compared with 16% for 28-day-old nitrate-supplied plants and 12% for 21-day-old nitrate-supplied plants. Shoot dark respiration was similar for all three plant groups, varying between 7.9% and 9.0% of the apparent photosynthate.The increased respiratory loss by the roots of the N(2)-fixing plants was not compensated for by increased net photosynthetic effectiveness. Canopy photosynthesis expressed on a leaf area basis was similar for 28-day-old N(2)-fixing plants (15.5 milligrams CO(2) square decimeter per hour) and 21-day-old nitrate-supplied plants (14.5 milligrams CO(2) square decimeter per hour). Both were similar in total canopy leaf area. The larger nitrate-supplied plants (28-day-old) had lower photosynthetic rates (12.5 milligrams CO(2) square decimeter per hour), presumably due to self-shading of the leaves.These data indicate that, during the early stages of plant development, dependence solely on N(2)-fixation is an expensive process compared to nitrate reduction in nitrate-supplied plants, since the N(2)-fixing plants retained 8% to 12% less of their photosynthate as dry matter.

Journal Article↗

PubMed1983

Soybean mutants lacking constitutive nitrate reductase activity : I. Selection and initial plant characterization.

The objectives of this study were to select and initially characterize mutants of soybean (Glycine max L. Merr. cv Williams) with decreased ability to reduce nitrate. Selection involved a chlorate screen of approximately 12,000 seedlings (progeny of mutagenized seed) and subsequent analyses for low nitrate reductase (LNR) activity. Three lines, designated LNR-2, LNR-3, and LNR-4, were selected by this procedure.In growth chamber studies, the fully expanded first trifoliolate leaf from NO(3) (-)-grown LNR-2, LNR-3, and LNR-4 plants had approximately 50% of the wild-type NR activity. Leaves from urea-grown LNR-2, LNR-3, and LNR-4 plants had no NR activity while leaves from comparable wild-type plants had considerable activity; the latter activity does not require the presence of NO(3) (-) in the nutrient solution for induction and on this basis is tentatively considered as a constitutive enzyme. Summation of constitutive (urea-grown wild-type plants) and inducible (NO(3) (-)-grown LNR-2, LNR-3, or LNR-4 plants) leaf NR activities approximated activity in leaves of NO(3) (-)-grown wild-type plants. Root NR activities were comparable in wild-type and mutant plants grown on NO(3) (-), and roots of both plant types lacked constitutive NR activity when grown on urea. In both growth chamber- and field-grown plants, oxides of nitrogen [NO((x))] were evolved from young leaves of wild-type plants, but not from leaves of LNR-2 plants, during in vivo NR assays. Analysis of leaves from different canopy locations showed that constitutive NR activity was confined to the youngest three fully expanded leaves of the wild-type plant and, therefore, on a total plant canopy basis, the NR activity of LNR-2 plants was approximately 75% that of wild-type plants. It is concluded that: (a) the NR activity in leaves of NO(3) (-)-grown wild-type plants includes both constitutive and inducible activity; (b) the missing NR activity in LNR-2, LNR-3, and LNR-4 leaves is the constitutive component; and (c) the constitutive NR activity is associated with NO((x)) evolution and occurs only in physiologically young leaves.

Journal Article↗

PubMed1987

Nodule activity and allocation of photosynthate of soybean during recovery from water stress.

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (psi w) of -2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule psi w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule psi w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N2-fixation activity.

Acetylene↗

PubMed1992

The Role of Ribulose-1,5-Bisphosphate Regeneration in the Induction Requirement of Photosynthetic CO(2) Exchange under Transient Light Conditions.

The temporally variable light environment of natural plant canopies presents distinct limitations to carbon assimilation, partially as a result of the photosynthetic induction requirement that develops when leaves are shaded. This study was undertaken with soybean (Glycine max L.) leaves to further identify factors contributing to the activation state of the fast component of induction during low photosynthetic photon flux density (PPFD) periods. Determination of pool sizes of carbon reduction cycle intermediates at low light and upon return to saturating light indicated that different limitations to photosynthetic activity arise over the time course of a 10-minute low PPFD period. Photosynthetic activity upon reillumination was limited by the regeneration of ribulose 1,5-P(2). There was an increase in the levels of fructose 1,6-P(2), sedoheptulose 1,7-P(2), triose-P, ribose 5-P, and ribulose 5-P pools, indicating inactivation of stromal enzymes, most notably fructose 1,6-bisphosphatase, sedoheptulose 1,7-bisphosphatase, and ribulose 5-P kinase. The fast-induction component was the most important factor limiting assimilation during rapid, brief light transients, during which the decay of the slow component was minimal. This may be particularly significant for upper leaves in soybean canopies that generally experience very rapid light transients.

Journal Article↗

PubMed2004

Microgeographic countergradient variation in the wood frog, Rana sylvatica.

Prior studies have shown that macrogeographic gradients in temperature associated with latitude and altitude can lead to countergradient patterns of variation in a number of taxa: individuals from colder environments are known to grow or develop faster than their conspecifics from warmer environments when placed in a common setting. In this study, I hypothesized that countergradient variation also is important at microgeographic scales. The wood frog, Rana sylvatica, breeds in open-canopied, temporary wetlands as well as those heavily shaded by vegetation. Shading leads to cooler thermal environments that are associated with embryonic development rates as much as 50% slower than those in unshaded wetlands. Wetlands with contrasting canopy environments are often found within tens or hundreds of meters of each other. In a common garden experiment, embryos from nearby natural wetlands displayed countergradient variation: individuals collected from shaded wetlands developed up to 12% faster than those collected from relatively unshaded wetlands. The results of this study suggest that the concept of countergradient variation may be extended to small scales of space. In addition, the rate and scale of vegetation dynamics (the agent of wetland shading) imply that divergence in development among residents of nearby wetlands may be relatively rapid, on the order of decades.

Acclimatization↗

PubMed2006

Does disturbance enhance genotypic diversity in clonal organisms? A field test in the marine angiosperm Zostera marina.

Physical disturbance has often been invoked to control genotypic diversity in sessile clonal organisms, yet experimental evidence is lacking. I studied the effects of physical disturbance on genet dynamics and genotypic diversity in a clonal marine angiosperm, Zostera marina (eelgrass). In replicated plots of 1 m2, the vegetation canopy was removed in gaps of zero (control), 25%, 50% and 75% of the area (n = 6 replicates). Before removal and during two consecutive years, the genotypic composition was determined using genetic markers (DNA microsatellites) in a 5 x 5 pixel grid per plot. An aggregate index of genet dynamics summarizing recruitment, increase, loss and decrease of clones was maximal at intermediate disturbance levels (quadratic polynomial P = 0.02). Physical disturbance also increased the occurrence of new genotypes, possibly reflecting recruitment (linear model, P < 0.05). Contrary to expectations, there was no competitive advantage of more heterozygous genotypes over less heterozygous ones. In the absence of disturbance, in particular, clones with lower individual heterozygosity were more likely to increase in area over a 1-year time period than more heterozygous ones, while there was no such correlation in plots with disturbance (logistic model, P(disturbance x heterozygosity) = 0.036). Undisturbed plots revealed background recruitment independent of canopy gaps, suggesting that Z. marina exhibits a strategy of continual recruitment. Effects of experimental disturbance (linear or quadratic) on clonal diversity were not detectable. Instead, initial (pretreatment) clonal diversity accounted for between 68% and 91% of the variance in diversity, indicating remarkable resilience of genotypic diversity in the face of physical disturbance.

Environment↗

PubMed2006

Parallel evolution of the sexes? Effects of predation and habitat features on the size and shape of wild guppies.

Environmental gradients often lead to the parallel evolution of populations and species. To what extent do such gradients also lead to parallel evolution of the sexes? We used guppies (Poecilia reticulata) to examine the parallel and independent (sex-specific) aspects of population divergence in response to predation and habitat features. Geometric morphometrics was used to analyse size and shape variation for 1335 guppies from 27 to 31 sites sampled in each of 2 years. Body size showed strong parallel population divergence; both sexes were larger at sites with a more open canopy and with higher flow. Body shape showed a mixture of parallel and independent population divergence. The strongest and most consistent effects were (1) high-predation sites had males with smaller heads and deeper caudal peduncles, (2) open-canopy sites had females with smaller heads and more distended abdomens and (3) high-flow sites had males and females with smaller heads and deeper caudal peduncles.

Animals↗

PubMed1985

Aerial Dispersal of Epiphytic Bacteria over Bean Plants.

Plant canopies are strong sources of bacterial aerosols during sunny days when the leaves are dry. Bacterial concentration, upward flux, and deposition onto exposed petri plates were measured over snap beans during three growing seasons. A net upward flux of bacteria occurred only during the warm part of sunny days, not at night when leaves were wet with dew or when a thermal inversion was present. Aerosol source strength was positively correlated with wind speed. Upward fluxes were higher on days after rain than on days when the soil was dry. Other unidentified sources of variability in source strength probably exist. Canopy-level deposition, apparently due to intermediate-scale transport of bacteria in fairly concentrated clouds, can occur in the early evening.

Journal Article↗

PubMed1981

Effect of quiet sleep on resting and CO2-stimulated breathing in humans.

We examined the effects of different levels of inspired CO2 on ventilation and the pattern of breathing in healthy adults during the awake and the stage II quiet-sleep states. During both states, subjects were studied supine with their heads enclosed in a canopy. Tidal volume (VT) was determined from quantitative measurements of abdominal and rib cage excursions with magnetometers. Inspired CO2 was raised by blending CO2-enriched gas into the airflow, which continuously flushed the canopy. During sleep, while room air was breathed, VT decreased significantly from 410 to 360 ml, and respiratory rate also fell from 17 to 16 breaths/min. As a consequence, ventilation was significantly reduced from 6.5 to 5.8 l/min, and end-tidal CO2 partial pressure (PCO2) rose from 39.1 to 42.5 Torr. Ventilatory responses to CO2 were reduced, on the average, during sleep to 79% of waking levels. The change in average inspiratory flow produced by CO2 was also less during sleep. Waking and sleeping ventilatory responses to CO2 correlated inversely with the rise in end-tidal PCO2 when room air was breathed during sleep. At all levels of VT, the rib cage contribution to VT was greater during quiet sleep than during wakefulness. These findings suggest that quiet sleep, in addition to depressing ventilation and the response to CO2 alters the manner in which VT is attained by rib cage and abdominal displacements.

Abdomen↗

PubMed1994

Low CSF 5-HIAA concentrations and severe aggression and impaired impulse control in nonhuman primates.

OBJECTIVE: The purpose of this study was to examine the relationship between behavior and serotonin by using a nonhuman primate model of aggression and impulse control. METHOD: During a routine capture and medical examination, 26 adolescent male rhesus macaques (Macaca mulatta) were selected as subjects from a free-ranging population of 4,500 rhesus monkeys inhabiting a 475-acre sea island. Physiological data were obtained from 22-23 of the subjects. Blood and CSF samples were obtained, and each subject was fitted with a radio transmitter collar for rapid location. The subjects were released into their social groups, and quantitative behavioral observations were made over a 3-month period. RESULTS: CSF 5-hydroxyindoleacetic acid (5-HIAA) concentrations were inversely correlated with "escalated" aggression, i.e., a measure of more intense or severe aggression as defined by the ratio of chases and physical assaults to all aggressive acts. CSF 5-HIAA concentrations were significantly lower in those subjects who showed evidence of physical wounding than in subjects with no wounds. Low CSF 5-HIAA concentrations were also correlated with greater risk-taking as determined by an analysis of leaping behaviors in the forest canopy. The ratio of long leaps (leaps that traversed the longest distances at dangerous heights) to all leaps was negatively correlated with CSF 5-HIAA concentrations. CONCLUSIONS: Adolescent male rhesus macaques with low CSF 5-HIAA concentrations are at risk for 1) exhibiting more violent forms of aggressive behavior and 2) loss of impulse control as evidenced by greater risk taking during movement through the forest canopy.

Aggression↗

PubMedDate not supplied

Comparison of two systems of measuring energy expenditure.

BACKGROUND: Health care professionals typically use resting metabolic rate (RMR) via indirect calorimetry to determine a person's energy expenditure. Traditional indirect calorimetry measurements involve an expensive, cumbersome piece of equipment that requires careful calibration. The recent development of a handheld indirect calorimeter makes it easier to measure RMR. The purpose of this study was to compare simultaneous measurements of RMR with handheld and traditional indirect calorimeters. METHODS: Healthy, free-living subjects (n = 50) age 18 years and older were tested simultaneously with both indirect calorimeters. All subjects breathed through the handheld device using a mouthpiece while wearing noseclips to prevent leaks. The handheld indirect calorimetry device was placed inside a canopy. The exhaled gas from the handheld was positioned directly over the inlet to the port delivering gases to the traditional device's mixing chamber. The canopy facilitated the simultaneous collection of all expired gases into the traditional device. During the measurement, oxygen consumption and RMR were continuously recorded on a personal computer. RESULTS: Mean oxygen consumption and RMR did not significantly differ between the two devices, with a mean difference of 0.58 +/- 15.33 mL/min (p = .790) and 4.66 +/- 113.39 kcal/day (p = .773) and an absolute difference of 12.3 +/- 8.99 mL/min and 86.58 +/- 72.32 kcal/day, respectively. Correlation coefficients for oxygen consumption and RMR were 0.945 and 0.941, respectively. CONCLUSIONS: No significant difference was found between the measurements of indirect calorimetry with the MedGem (HealtheTech, Golden, CO) device compared with the DeltaTrac device (Datex-Ohmeda, Madison, WI). These findings suggest that the handheld indirect calorimeter may provide an accurate measure of oxygen consumption and RMR measurements for spontaneously breathing subjects.

Adult↗

PubMedDate not supplied

Human gradient-layer calorimeter: development of an accurate and practical instrument for clinical studies.

A whole body gradient-layer calorimeter was designed for thermophysiologic studies in hospitalized patients. The instrument was assembled in a room adjoining a metabolic ward. The patient lies recumbent on a stretcher which is wheeled into the calorimeter on tracks. Once inside, the patient's head extends through one wall into a clear plastic canopy. The canopy is partially open on one side and is the entry point for fresh air into this open-circuit system. Heat flux transducers in the calorimeter walls, a thermopile in the exit air stream, and a platemeter in conjunction with wet and dry bulb thermometers allow measurement of total, wet, and dry heat losses from the subject. All calorimeter output signals are routed to a microcomputer system which processes the data and provides real-time output of results. A mannequin heat source is used to calibrate the gradient layer. Testing with a variety of wet/dry heat sources indicate total, wet, and dry heat measurements are accurate to within 2-3%. A typical study of resting energy expenditure requires 1 hr, and protocols of up to 6 hr are well tolerated. The calorimeter has proven to be reliable, accurate, and easy to operate. These qualities, combined with good patient tolerance, make it ideal for metabolic studies.

Calorimetry↗

PubMed1994

A polymorphic microsatellite marker from the tropical tree Dryobalanops lanceolata (Dipterocarpaceae).

Di-nucleotide microsatellites were isolated from a genomic library of a tropical tree species, Dryobalanops lanceolata, in Sarawak, for the purpose of using them as hypervariable genetic markers to study the pollen-mediated gene flow. Among 1600 recombinant clones, in total 20 clones gave positive signals when hybridized with oligonucleotides with the three different repeat motifs, GT, CA and CT. Estimations of abundance of (GT)n/(CA)n and (GA)n/(CT)n dinucleotide repeats in D. lanceolata genome revealed to be one in every 84 kb and 80 kb, respectively. Among six sequenced microsatellite loci, one was selected to synthesize PCR primers to amplify the microsatellite. PCR product size of the locus was variable among different individuals, which is attributed to the different number of di-nucleotide repeats. The same microsatellite genotype was detected in the trunk and canopy of a single large tree, indicating the utility of trunk tissue as the source of DNA for the population genetic study of tropical tree species, the canopy of which is usually difficult to approach.

Base Sequence↗

PubMedDate not supplied

Machine vision extracted plant movement for early detection of plant water stress.

A methodology was established for early, non-contact, and quantitative detection of plant water stress with machine vision extracted plant features. Top-projected canopy area (TPCA) of the plants was extracted from plant images using image-processing techniques. Water stress induced plant movement was decoupled from plant diurnal movement and plant growth using coefficient of relative variation of TPCA (CRV[TPCA)] and was found to be an effective marker for water stress detection. Threshold value of CRV(TPCA) as an indicator of water stress was determined by a parametric approach. The effectiveness of the sensing technique was evaluated against the timing of stress detection by an operator. Results of this study suggested that plant water stress detection using projected canopy area based features of the plants was feasible.

Ecological Systems, Closed↗

PubMed2006

Fluorescence sensing techniques for vegetation assessment.

Active fluorescence (F) sensing systems have long been suggested as a means to identify species composition and determine physiological status of plants. Passive F systems for large-scale remote assessment of vegetation will undoubtedly rely on solar-induced F (SIF), and this information could potentially be obtained from the Fraunhofer line depth (FLD) principle. However, understanding the relationships between the information and knowledge gained from active and passive systems remains to be addressed. Here we present an approach in which actively induced F spectral data are used to simulate and project the magnitude of SIF that can be expected from near-ground observations within selected solar Fraunhofer line regions. Comparisons among vegetative species and nitrogen (N) supply treatments were made with three F approaches: the passive FLD principle applied to telluric oxygen (O2) bands from field-acquired canopy reflectance spectra, simulated SIF from actively induced laboratory emission spectra of leaves at a series of solar Fraunhofer lines ranging from 422 to 758 nm, and examination of two dual-F excitation algorithms developed from laboratory data. From these analyses we infer that SIF from whole-plant canopies can be simulated by use of laboratory data from active systems on individual leaves and that SIF has application for the large-scale assessment of vegetation.

Agriculture↗

PubMed2001

Adaptive divergence in plasticity in natural populations of Impatiens capensis and its consequences for performance in novel habitats.

We tested for adaptive differentiation between two natural populations of Impatiens capensis from sites known to differ in selection on plasticity to density. We also determined the degree to which plasticity to density within a site was correlated with plastic responses of experimental immigrants to foreign sites. Inbred lines, derived from natural populations in an open-canopy site and a woodland site, were planted reciprocally in both original sites at naturally occurring high densities and at low density. The density manipulation represents environmental variation typically experienced within the site of a given population, and the transplant manipulation represents environmental differences between sites of different populations. Internode elongation, meristem allocation, leaf length, flowering date, and total lifetime fitness were measured. Genotypes originating in the open site, where selection favored plasticity of first internode length and flowering time (Donohue et al. 2000a), were more plastic in those characters than genotypes originating from the woodland site, where plasticity was maladaptive. Therefore, these two populations appear to have responded to divergent selection on plasticity. Plasticity to density strongly resembled plasticity to site differences for many characters, suggesting that similar environmental factors elicit plasticity both to density and to overhead canopy. Thus, plasticity that evolved in response to density variation within a site influenced phenotypic expression in the foreign site. Plastic responses to site caused immigrants from foreign populations to resemble native genotypes more closely. In particular, immigrants from the open site converged toward the selectively favored early-flowering phenotype of native genotypes in the woodland site, thereby reducing potential fitness differences between foreign and native genotypes. However, because genotypes from the woods population were less plastic than genotypes from the sun population, phenotypic differences between populations were greatest in the open site at low density. Therefore, population differences in plasticity can cause genotypes from foreign populations to be more strongly selected against in some environments than in others. However, genetic constraints and limits to plasticity prevented complete convergence of immigrants to the native phenotype in any environment.

Adaptation, Physiological↗

PubMed2001

Multi-waveband solar irradiance on tree-shaded vertical and horizontal surfaces: cloud-free and partly cloudy skies.

Irradiance measurements of short wave (SW), photosynthetically active (PAR), ultraviolet-A (UVA) and ultraviolet-B (UVB) solar radiations were made on horizontal and vertical surfaces in the shade of trees under cloud-free and partly cloudy skies. All measurements were referenced to the irradiance of a horizontal surface above the canopy. For horizontal shaded surfaces under cloud-free skies, the values of the ratio (Rh) of below- to above-canopy horizontal irradiance were similar for the UVA and UVB wavebands and for the SW and PAR wavebands. However, Rh for the UV wavebands differed from that for the PAR and SW wavebands. Overall, values of Rh in the shade typically varied as PAR < SW << UVA < UVB. The irradiance ratios for vertical surface in the shade typically varied as UVB > UVA = SW > PAR. In absolute terms, UVB irradiance (Ih) on tree-shaded horizontal surfaces increased relative to a cloud-free sky when a translucent cirroform cloud was in front of the sun, but decreased when the cloud was in a region of sky away from the sun. Translucent cirroform cloud cover also tended to decrease the UVB irradiance (Iv) for a shaded vertical surface (either facing the sun or south) relative to that under cloud-free skies, regardless of where the clouds were in the sky. In all other wavebands the shaded Ih and Iv increased under translucent cirroform cloud cover relative to cloud-free skies, regardless of where the clouds were in the sky.

Humans↗