The Influence of Temperature and Soil Water Deficit on the Development and Morphology of Groundnut (Arachis hypogaea L.)

The rate/temperature relation of several developmental processesin groundnut was examined in a suite of temperature-controlledglasshouses maintained at mean air temperatures of 19, 22, 25,28 and 31 °C. The sensitivity of the various processes tosoil water deficit was also examined. When the relation between rate and temperature was linear, measurementswere analysed in terms of thermal time (°Cd) and an extrapolatedbase temperature (T_b) at which the rate was zero. T_b was conservative(10 °C) for leaf appearance, branching, flowering, peggingand podding. A higher value of T_b for seedling emergence (16°C) was probably an artifact caused by soil pathogens. Leafappearance and branching were more sensitive to soil water deficitthan the other processes examined. Key words: Temperature, Soil water deficit, Development, Groundnut     

The Influence of Temperature on Seed Germination Rate in Grain Legumes: II. INTRASPECIFIC VARIATION IN CHICKPEA (Cicer arietinum L.) AT CONSTANT TEMPERATURES

Positive linear relationships were shown between constant temperaturesand the rates of progress of germination to different percentiles,G, for single populations of each of five genotypes of chickpea(Cicer anetinum L.). The base temperature, T_b, at which therate of germination is zero, was 0·0°C for all germinationpercentiles of all genotypes. The optimum temperature, T_o(G),at which rate of germination is most rapid, varied between thefive genotypes and also between percentiles within at leastone population. Over the sub-optimal temperature range, i.e.from T_b to T_o(G), the distribution of thermal times within eachpopulation was normal. Consequently a single equation was appliedto describe the influence of sub-optimal temperatures on rateof germination of all seeds within each population of each genotype.The precision with which optimum temperature, T_b(G), could bedefined varied between populations. In each of three genotypesthere was a negative linear relationship between temperatureabove T_b(G) and rate of germination. For all seeds within anyof these three populations thermal time at supra-optimal temperatureswas constant. Variation in the time taken to germinate at supra-optimaltemperatures was a consequence of normal variation in the ceilingtemperature, T_o(G)—the temperature at or above which rateof progress to germination percentile G is zero. A new approachto defining the response of seed germination rate to temperatureis proposed for use in germplasm screening programmes. In two populations final percentage germination was influencedby temperature. The optimum constant temperature for maximumfinal germination was between 10°C and 15°C in thesepopulations; approximately 15°C cooler than the optimumtemperature for rate of germination. It is suggested that laboratorytests of chickpea germination should be carried out at temperaturesbetween 10°C and 15°C. Key words: Chickpea, seed germination rate, temperature     

The Influence of Temperature on Seed Germination in Cultivars of Common Bean

Common bean (Phaseolus vulgaris L.) is grown over a wide rangeof environments, including sites with low or high soil temperaturesat sowing time. To describe the temperature responseof seedgermination, 20 bean genotypes were evaluated using a rolledpaper towel system with 11 constant temperatures ranging from12 to 34 °C. Germination response was characterized by fittingcumulative counts using a maximum-likelihood analysis. Rateof germination increased from abase temperature (T_b) typicallynear 8 °C to an optimal development temperature (T_o) of29 to 34 °C. T_b did not differ among common bean genotypes.Mesoamerican germplasm showed slightlyhigher T_o than Andeangermplasm, but there was large variation in T_o within each ofthe two gene pools. The single accession of tepary bean (P.acutifolius) evaluated appeared to be the mosttolerant to highgermination temperatures. Key words: Common bean, seed germination rate, temperature     

Response to Temperature in a Stand of Pearl Millet: 10. PARTITION OF ASSIMILATE

Effects of temperature on partition of assimilate between leaves,stems and panicles of pearl millet are analysed in terms ofa duration (t_w) over which a structure increased in weight,and a partition factor (p)—the fraction of new dry matterallocated to the structure during t_w. The value of tw was, forall structures, inversely proportional to temperature abovea base of 10 °C and below an optimum of 28 to 30 °C.For stems and panicles, the value of p was, with one exception,little affected by temperature. The dry weight of these structureswas, therefore, proportional to t_w, and decreased with risein temperature. (The exception was panicles at the lowest temperature,19 °C, for which p was reduced by 40% because few grainswere set.) For leaves, however, p increased with rise in temperature,counteracting the effect on t_w, such that dry weight changedlittle with temperature. The optimum temperature for reproductiveyield was 22 °C, but the proportion of the total dry matterallocated to reproductive structures changed little between22 °C and 31 °C. Key words: Pearl millet, temperature, thermal time, partitioning     

The Effects of Priming and 'Natural' Differences in Quality amongst Onion Seed Lots on the Response of the Rate of Germination to Temperature and the Identification of the Characteristics under Genotypic Control

Ellis, R. H. and Butcher, P. D. 1988. The effects of primingand ‘natural’ differences in quality amongst onionseed lots on the response of the rate of germination to temperatureand the identification of the characteristics under genotypiccontrol —J. exp. Bot. 39: 935–950. A screening procedure was applied to define the response ofthe rate of seed germination to sub-and supra-optimal temperaturesfor different lots or sub-lots of two onion (Allium cepa L.)cultivars.Three sub-lots of the cultivar White Lisbon were derived froma control lot by osmotic priming (–1.4 MPa, 20 °C.7 d) alone, by priming and drying and by priming, drying andsubsequently storing the seeds for 7 weeks at 2–5 °C.The major effect of priming was to reduce the thermal time forgermination at both sub- and supra-optimal temperatures. Primingalone also altered the distribution of thermal times at sub-optimaltemperatures. A new equation is presented to describe this variation.In contrast, priming had no consistent effect on base temperature(T_b and little effect on the distribution of ceiling temperatures[T_e(G)]. For the control lot of White Lisbon T_b was 4°C,whilst the best common estimate of T_b for all four sub-lotswas 3.5°C. The mean estimate of T_c(50) for the control,primed and primed and dried sub-lots was 35.5°C.Comparisonof three lots of the cultivar Senshyu Semi Globe Yellow of widely-differingviability showed substantial differences in the thermal timefor germination at sub-optimal temperatures, but no significantdifferences in T_b (P>0.10), the common estimate being 4°C.There was a significant negative correlation between probitpercentage viability and the logarithm of the thermal time for50% germination at sub-optimal temperatures amongst the threelots (P<0.05). The work suggests that base temperature forgermination is a genotypic characteristic which is unaffectedby differences in seed quality. It also shows that the effectof priming, quantified as a reduction in thermal time requirementsfor germination, varies amongst the seeds within a lot. Key words: -Onion, seed germination rate, temperature, priming     

Effects of Temperature and Water Loss on Terrestrial Locomotor Performance in Land Crabs: Integrating Laboratory and Field Studies

SYNOPSIS. Terrestrial and semi-terrestrial crustaceans are exposedto fluctuations in ambient temperature and conditions that favorevaporative water loss. These environmental stresses alter performancelimits in the laboratory and behavior in the field. The maximalrate of oxygen consumption, maximum aerobic speed, and endurancecapacity are greater at a body temperature (T_b) of 24°Cthan at 15°C or 30°C in the ghost crab, Ocypode quadrata.The total metabolic cost to move at the same relative speedis greater at a T_b of 24°C than at 15°C. Slower aerobickinetics at 15°C result in a smaller relative contributionof oxidative metabolism to total metabolic cost. However, therelative contributions from accelerated glycolysis are similarat both temperatures. When locomotion is intermittent, the totaldistance traveled before fatigue can be similar at Tbs of 15and 24°C but result from different movement and pause durationsat these temperatures. Performance limits of the ghost crabare negatively affected by dehydration and are sensitive torates of water loss. In the laboratory, endurance capacity ofthe fiddler crab, Uca pugilator, is greater at a T_b of 30°Cthan at 25°C. In the field, freely moving fiddler crabswith a T_b of 30°C travel at faster mean preferred speeds,as determined by motion analysis, than crabs at 25°C. Datafor land crabs support and advance general ectothermic modelsfor the effects of temperature and dehydration on locomotorperformance.     

Effects of Temperature and Water Potential on Germination, Radicle Elongation and Emergence of Mungbean

Controlled environment experiments were performed to determinethe effects of temperature and water potential on germination,radicle elongation and emergence of mungbean (Vigna radiata(L.) Wilczek cv. IPB-M79-17-79). The effects of a range of constant temperatures (15–45°C) and water potentials (0 to –2.2 MPa) on germinationand radicle elongation rates were studied using an osmoticumtechnique, in which seeds were held against a semi-permeablemembrane sac containing a polyethylene glycol solution. Linearrelationships were established between median germination time(Gt₅₀) and water potential at different temperatures, and betweenreciprocal Gt₅₀ (germination rate) and temperature at differentwater potentials. Germination occurred at potentials as lowas –2.2 MPa at favourable temperatures (30–40 °C),but was fastest at 40 °C when water was not limiting, withan estimated base temperature (T_b) of about 10 °C. Subsequentradicle elongation, however, was restricted to a slightly narrowertemperature range and was fastest at 35 °C. The conceptof thermal time was used to develop an equation to model thecombined effects of water potential and temperature on germination.Predictions made using this model were compared with the actualgermination obtained in a related series of experiments in columnsof soil. Some differences observed suggested the additionalimportance of the seed/soil/water contact zone in influencingseed germination in soil. Seedling emergence appeared to reflectfurther the radicle elongation results by occurring within anarrower range of temperatures and water potentials than germination.Emergence had an estimated T_b of 12.6 °C and was fastestat 35 °C. A soil matric potential of not less than about–0.5 MPa at sowing was required to obtain 50% or moreseedling emergence. Key words: Germination, temperature, water potential     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.): VII. INFLUENCE OF AFTER-RIPENING AND AGEING ON GERMINATION RESPONSES TO TEMPERATURE AND WATER POTENTIAL

The effects of storage conditions on the germination of developingmuskmelon (Cucumis melo L.) seeds were tested to determine whetherafter-ripening is required to obtain maximum seed vigour. Seedswere harvested at 5 d intervals from 35 (immature) to 60 (fullymature) days after anthesis (DAA), washed, dried, and storedat water contents of 3·3 to 19% (dry weight basis) at6, 20, or 30°C for up to one year. Germination was testedin water and in polyethylene glycol 8000 solutions ( –0·2to –1·2 MPa osmotic potential) at 15, 20, 25 or30°C. Germination percentages and rates (inverse of meantimes to radicle emergence) were compared to those of newlyharvested, washed and dried seeds. For 40 and 60 DAA seeds,one year of storage at 20°C and water contents <6·5%significantly increased germination percentages and rates at20°C, but had little effect on germination at 25 and 30°C.Storage reduced the estimated base temperature (T_b) and meanbase water potential (_b) for germination of both 40 and 60 DAAseeds by approximately 5°C and 0·3 MPa, respectively.Immature 35 DAA seeds showed the greatest benefit from storageat 3 to 5% water content and 30°C, as germination percentagesand rates increased at all water potentials (). Storage underthese same conditions had little effect on the germination ofmature seeds in water, but increased germination percentagesand rates at reduced 's. Accelerated ageing for one month at30°C and water contents from 15 to 19° increased germinationrates and percentages of mature seeds at reduced 's, but longerdurations resulted in sharp declines in both parameters. Immatureseeds lost viability within one month under accelerated ageingconditions. An after-ripening period is required at all stagesof muskmelon seed development to expand the temperature andwater potential ranges allowing germination and to achieve maximumgerminability and vigour. Post-harvest dormancy is deepest atthe point of maximum seed dry weight accumulation and declinesthereafter, both in situ within the ripening fruit and duringdry storage. Key words: Muskmelon, Cucumis melo L., seed, development, dormancy, germination, vigour, after-ripening     

Time, Temperature and Germination of Pearl Millet (Pennisetum typhoides S. & H.): I. CONSTANT TEMPERATURE

The germination of pearl millet (Pennisetum typhoides S. &H.) seeds was investigated at constant temperatures between12 ?C and 47 ?C on a thermal gradient plate. The rate of germination increased linearly with temperaturefrom a base T_b to a sharply defined optimum T_o beyond whichthe rate decreased linearly with temperature, reaching zeroat T_m. The linearity of the response both above and below T_oallowed time and temperature to be combined in a thermal timeat which a specified fraction of the seeds germinated. Withinthe population T_b and T_m were constant.     

Heat stroke: opioid-mediated mechanisms

Romanovsky, Andrej A., and Clark M. Blatteis. Heatstroke: opioid-mediated mechanisms. J. Appl.Physiol. 81(6): 2565-2570, 1996.In our previousstudy in guinea pigs, intensive and prolonged intraperitoneal heating(IPH) caused heat stroke characterized by high mortality andaccompanied by two paradoxical phenomena: ear skin vasoconstriction ata high body temperature (T_b)(hyperthermia-induced vasoconstriction) and a post-IPHT_b fall at an ambient temperature (T_a) below thermoneutrality(hyperthermia-induced hypothermia). In this study, we tested thehypothesis that the mechanisms of the two phenomena involve endogenousopioid agonists. Experiments were conducted in 24 unanesthetized,lightly restrained guinea pigs, each chronically implanted with anintraperitoneal thermode and intrahypothalamic thermocouple. Thethermoregulatory effects of a wide-spectrum opioid-receptor antagonist,naltrexone (NTX; 50 or 0 µmol/kg sc), were studied in IPH-inducedheat stroke and under normal conditions. IPH was accomplished byperfusing (50 ml/min; 80 min) water (45°C) through the thermode.T_a was maintained at ~24°C.Skin vasodilation occurred at the onset of IPH but later changed tovasoconstriction despite high T_band continuing IPH. IPH-induced hyperthermia (1.8 ± 0.1°C) was followed by a post-IPH T_b fall (5.1 ± 0.7°C; calculated for the survivors only). The 48-h mortality ratewas 50%. NTX prevented the hyperthermia-induced vasoconstriction andattenuated the hyperthermia-induced hypothermia (1.8 ± 0.4°C). None of the NTX-treated animals died. The effects of NTX onT_b regulation under normalconditions were minor. These results indicate that the phenomena ofboth hyperthermia-induced vasoconstriction and hyperthermia-inducedhypothermia are opioid dependent. The latter is speculated to reflectopioid-mediated inhibition of metabolism; the former is thought toresult from opioid-induced hemodynamic alterations. Because bothphenomena did not occur in the NTX-treated survivors, the skinvasoconstriction at high T_b andthe posthyperthermia T_b fall maybe viewed as markers of the severity of heat stroke. It is suggestedthat opioid antagonists may have therapeutic potential in heat-induceddisorders.

     

Chronic hormone replacement therapy alters thermoregulatory and vasomotor function in postmenopausal women

Brooks, E. M., A. L. Morgan, J. M. Pierzga, S. L. Wladkowski, J. T. O'Gorman, J. A. Derr, and W. L. Kenney. Chronic hormone replacement therapy alters thermoregulatory and vasomotor function in postmenopausal women. J. Appl.Physiol. 83(2): 477-484, 1997.This investigationexamined effects of chronic (2 yr) hormone replacement therapy (HRT),both estrogen replacement therapy (ERT) and estrogen plus progesteronetherapy (E+P), on core temperature and skin blood flow responses ofpostmenopausal women. Twenty-five postmenopausal women [9 not onHRT (NO), 8 on ERT, 8 on E+P] exercised on a cycle ergometer for1 h at an ambient temperature of 36°C. Cutaneous vascularconductance (CVC) was monitored by laser-Doppler flowmetry, and forearmvascular conductance (FVC) was measured by using venous occlusionplethysmography. Iontophoresis of bretylium tosylate was performedbefore exercise to block local vasoconstrictor (VC) activity at oneskin site on the forearm. Rectal temperature (T_re) was ~0.5°C lower forthe ERT group (P < 0.01) comparedwith E+P and NO groups at rest and throughout exercise. FVC: mean body temperature (T_b) and CVC:T_b curves were shifted~0.5°C leftward for the ERT group(P < 0.0001). Baseline CVC wassignificantly higher in the ERT group(P < 0.05), but there was nointeraction between bretylium treatment and groups once exercise wasinitiated. These results suggest that1) chronic ERT likely acts centrally to decrease T_re,2) ERT lowers theT_re at which heat-loss effector mechanisms are initiated, primarily by actions on active cutaneous vasodilation, and 3) addition ofexogenous progestins in HRT effectively blocks these effects.

     

Genotypic Differences in the Temperature Responses of Tropical Crops: II. SEEDLING EMERGENCE AND LEAF GROWTH OF GROUNDNUT (ARACHIS HYPOGAEA L.) AND PEARL MILLET (PENNISETUM TYPHOIDES S. & H.)

Mohamed, H. A., Clark, J. A. and Ong, C. K. 1988. Genotypicdifferences in the temperature responses of tropical crops.II. Seedling emergence and leaf growth of groundnut (Arachishypogaea L.) and pearl millet (Pennisetum typhoides S. &H.).—J. exp. Bot. 39: 1129-1135. Measurements of seedling emergence and leaf growth of five milletand seven groundnut genotypes were made at soil temperaturesranging from 7 to 27?C. The rate of seedling emergence (R_e)varied greatly between millet genotypes but R_e was remarkablysimilar in groundnut genotypes. In pearl millet there is a strongcorrelation between the rate of germination and the rate ofleaf production, hourly leaf extension and seedling emergence.The results are discussed in terms of the thermal time requirementsof various processes. Key words: Temperature, emergence, groundnut, millet     

Effects of Priming and Endosperm Integrity on Seed Germination Rates of Tomato Genotypes: I. GERMINATION AT SUBOPTIMAL TEMPERATURE

The bases of differences in germination rates (GR_g = inverseof time to germination [t_g] of percentage g) among three cold/salt-toleranttomato (Lycopersicon esculentum Mill.) accessions (PI 341988,PI 120256, and PI 174263) and one cold/salt-sensitive tomatocultivar (T5) were investigated. The effects of seed priming(6 d imbibition in aerated –1.2 MPa polyethylene glycolsolution at 20 ?C followed by redrying) and of removing theendosperm/testa cap covering the radicle on the temperaturesensitivity of GR_g, and the interaction of these treatmentswith genotypes, were also examined. GR_g decreased linearly withdecreasing temperature for all genotypes and seed treatments.The minimum or base temperatures for germination (T_b) variedby 1 ?C among the tomato lines, so genotypic differences inGR_g were due to differing thermal time requirements for germination.The mean thermal time requirement for germination of T5 seeds was 22% and 19% greater than that of PI 341988 andPI 120256 seeds, respectively, but only 9% greater than thatof PI 174263 seeds. Seed priming did not lower Tb of any genotype,but significantly reduced by 24, 49, 41, and 49% in T5, PI 341988, PI 120256, and PI 174263, respectively,indicating that priming increased the rate at which the seedsprogressed towards germination when T>T_b, but did not lowerthe minimum temperature at which germination could occur. Primingincreased the GR_g of T5 seeds to equal or exceed those of control(non-primed) seeds of the cold/salt-tolerant genotypes at anyT>T_b, but the PI lines exhibited an even greater responseto priming. Times to germination within each seed lot were normallydistributed on a logarithmic scale. Priming increased the variancein tg within a seed lot when compared to control seeds. However,the variation in thermal time for germination between the 10thand 90th percentiles of the seed population (_T(10–90))was relatively unaffected by priming due to the reduction in in primed seeds. Removing the endosperm cap and testa opposite the radicle tip decreased almost 6-fold and and reduced T_b by 5 ?C in T5 and PI 341988,implicating processes in the endosperm/testa as the limitingfactors in germination at suboptimal temperatures. Key words: Lycopersicon esculentum Mill., tomato, genetic variation, seed priming, thermal time, germination rate     

Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise

González-Alonso, José, RicardoMora-Rodríguez, Paul R. Below, and Edward F. Coyle.Dehydration markedly impairs cardiovascular function inhyperthermic endurance athletes during exercise. J. Appl. Physiol. 82(4): 1229-1236, 1997.Weidentified the cardiovascular stress encountered by superimposingdehydration on hyperthermia during exercise in the heat and themechanisms contributing to the dehydration-mediated stroke volume (SV)reduction. Fifteen endurance-trained cyclists [maximalO₂ consumption(O_{2 max}) = 4.5 l/min] exercised in the heat for 100-120 min and either became dehydrated by 4% body weight or remained euhydrated by drinkingfluids. Measurements were made after they continued exercise at 71%O_{2 max} for 30 minwhile 1) euhydrated with anesophageal temperature (T_es) of38.1-38.3°C (control); 2)euhydrated and hyperthermic (39.3°C);3) dehydrated and hyperthermic withskin temperature (T_sk) of34°C; 4) dehydrated withT_es of 38.1°C and T_sk of 21°C; and5) condition4 followed by restored blood volume. Compared withcontrol, hyperthermia (1°C T_esincrease) and dehydration (4% body weight loss) each separatelylowered SV 7-8% (11 ± 3 ml/beat;P < 0.05) and increased heart ratesufficiently to prevent significant declines in cardiac output.However, when dehydration was superimposed on hyperthermia, thereductions in SV were significantly (P < 0.05) greater (26 ± 3 ml/beat), and cardiac output declined 13% (2.8 ± 0.3 l/min). Furthermore, mean arterialpressure declined 5 ± 2%, and systemic vascular resistanceincreased 10 ± 3% (both P < 0.05). When hyperthermia wasprevented, all of the decline in SV with dehydration was due to reducedblood volume (~200 ml). These results demonstrate that thesuperimposition of dehydration on hyperthermia during exercise in theheat causes an inability to maintain cardiac output and blood pressurethat makes the dehydrated athlete less able to cope with hyperthermia.

     

Transverse Relaxation Time of Leaf Water Protons and Membrane Injury in Wheat (Triticum aestivum L.) in Response to High Temperature

The relationship between high temperature stress injury andtemperature dependence of the transverse relaxation time (T₂)of leaf water was examined using NMR in four cultivars of wheatdiffering in their sensitivity to high temperature stress. TheT₂declined with increasing temperature between 25 and 35 °C.A comparison of relative injury based on electrolyte leakageand T₂, between 40 and 50 °C, indicated that while membranepermeability increased with increasing temperature there wasan increase in T₂until 44 and 48 °C in susceptible and tolerantcultivars respectively, followed by a sharp decline. This patternof change in T₂with increasing temperature was consistent whetherthe same or different samples were used for each treatment temperature.Loss of temperature dependence of T₂after heat killing indicatedirreversible changes in T₂, probably due to the loss of membraneintegrity. Heat tolerant varieties, which suffered less membraneinjury, had a higher T₂compared to susceptible varieties. Tolerantvarieties also maintained the T₂of leaf water protons to highertemperatures than did sensitive varieties. This NMR-based, non-invasive,rapid technique could be used to efficiently detect heat injuryin leaf tissues. Copyright 1999 Annals of Botany Company Membrane integrity, transverse relaxation time, high temperature stress, Triticum aestivum L.     

Rate of uptake of CO by hemoglobin in pig erythrocytes as a function of PO2

Te Nijenhuis, Francis C. A. M., Lydia Lin, Gerko H. Moens,Adrian Versprille, and Robert E. Forster. Rate of uptake of CO byhemoglobin in pig erythrocytes as a function ofPO₂. J. Appl.Physiol. 81(4): 1544-1549, 1996.This study wasinitiated to obtain data on the rate of carbon monoxide (CO) uptake(_CO) by hemoglobin in pigerythrocytes to derive, in a later study, the pulmonary capillary bloodvolume (Qc) in pigs from the Roughton-Forster relationship. Blood fromfive different female pigs was used. The_CO, the milliliters of CO takenup by 1 ml of whole blood per minute per Torr CO tension, wasdetermined on each blood sample with a continuous-flow rapid-mixingapparatus and double-beam spectrophotometry at 37°C and pH 7.4 atfour or five different PO₂ values.Because the individual regression lines of _CO vs.PO₂ were not significantly different,a common regression equation was calculated:1/_CO = 0.0084 PO₂ + 0.63. The slope of thisregression line is significantly steeper than the reported slopes ofthe regression lines for human and dog erythrocytes measured under thesame conditions. Our results revealed that calculation ofQc in pigs by using _CO valuesfor human or dog erythrocytes would result in an underestimation of 51 and 50%, respectively.

     

A Temperature Effect on the Expression of Genotypic Differences in Flowering Induction in Antirrhinum majus

Three inbred lines of Antirrhinum majus and the F₁ generationsof crosses between them were scored for flowering time in ninegreenhouse and garden experiments. The inbreds fell into twogroups, the difference between which showed a marked interactionwith environments. The two lines (An 105, An 106) which weresimilar were earlier flowering than the third line (An 101)in those environments which produced generally early flowering,but were later than An 101 when the environmental conditionsled to late flowering. In all cases the F₁ generations wereat least as early as the earlier parent. Cabinet experiments identified temperature as the importantenvironmental factor when day length was kept constant at 16h. At 25°C, An 105 and An 106 were earlier than An 101 whileat 12°C, at which temperature the average flowering timewas much later, An 101 was earlier. The F₁ generations werelike An 105 and An 106 at 25°C but showed heterosis at 12°C. The differences in flowering time between genotypes were inall cases established by the time the first reproductive budsbecame visible (budding time). Thus a temperature differencewell outside the range of vernalizing temperatures is havinga striking effect on the phenotypic expression of genotypicdifferences determining the transition from vegetative to floweringdevelopment.     

Appropriate thermal manipulations eliminate tremors in rats recovering from halothane anesthesia

Grahn, D. A., M. C. Heller, J. E. Larkin, and H. C. Heller.Appropriate thermal manipulations eliminate tremors in ratsrecovering from halothane anesthesia. J. Appl.Physiol. 81(6): 2547-2554, 1996.Tremors arecommon in mammals emerging from anesthesia. To determine whetherappropriate thermal manipulations immediately before emergence fromanesthesia are sufficient to eliminate these tremors,electroencephalographic (EEG) and electromyographic (EMG) activities,hypothalamic temperature (T_hy),and O₂ consumption were monitoredin 12 rats recovering from halothane anesthesia under three thermalregimes. EEG and EMG activities were recorded throughout anesthesia andserved as feedback signals for controlling anesthetic depth. Duringanesthesia, T_hy was either1) allowed to fall to32-34°C, 2) maintained at37-39°C, or 3) allowed to fall to 32-34°C and then raised to 37-39°C. Whenhypothermic on emergence from anesthesia, all of the animals exhibitedpostanesthetic tremors that persisted untilT_hy values returned tonormothermia. None of the animals expressed postanesthetic tremors whennormothermic on emergence from anesthesia. In addition, the timebetween emergence from anesthesia (as determined by EEG/EMG parameters)and the initiation of coordinated motor activities was significantlydecreased in the normothermic animals.

     

Non-linearity in rate-temperature relations of germination in oilseed rape

Predominantly linear relations between germination rate andtemperature (over specific ranges) have hitherto been foundamong the main crop plants. Given linearity, accumulated temperatureabove a base (T_b) is a reliable predictor of germination time.In contrast, this paper shows marked non-linearities in theresponse of germination to temperature for four oilseed rapecultivars, two ‘double high’ (Martina and Askari)and ‘two double low’ (Rocket and Express). Linearregressions of 1/time to germination of given percentiles indicateT_b is about 3 C for all cultivars. However, consistent deviationsfrom linearity occur especially at low temperature, such thatgermination time at 5C is up to twice as fast as predictedfrom a linear model. Moreover, two of the cultivars show anincreasing proportion of seeds not germinating as temperatureis lowered. These seeds were still viable as demonstrated bytheir ability to germinate when transferred to warmer temperature.The consequence of non-linearity was to increase the spreadof time over which seeds germinated at low temperature. Thispaper defines the effects and indicates the margin of errorlikely to follow from applying linear rate/temperature modelsto whole populations. The findings have implications for thepropensity of different oilseed rape cultivars to become volunteerweeds and feral populations. Key words: Oilseed rape, germination, temperature, model, non-linear     

Ozone toxicity in the rat. III. Effect of changes in ambient temperature on pulmonary parameters

Wiester, Mildred J., William P. Watkinson, Daniel L. Costa,Kay M. Crissman, Judy H. Richards, Darrell W. Winsett, and Jerry W. Highfill. Ozone toxicity in the rat. III. Effect of changes inambient temperature on pulmonary parameters. J. Appl.Physiol. 81(4): 1691-1700, 1996.Pulmonarytoxicity of ozone (O₃) wasexamined in adult male Fischer 344 rats exposed to 0.5 parts/millionO₃ for either 6 or 23 h/day over 5 days while maintained at an ambient temperature(T_a) of either 10, 22, or34°C. Toxicity was evaluated by using changes in lung volumes andthe concentrations of constituents of bronchoalveolar lavage fluid thatsignal lung injury and/or inflammation. Results indicated thattoxicity increased as T_adecreased. Exposures conducted at 10°C were associated with thegreatest decreases in body weight and total lung capacity and thegreatest increases in lavageable protein, lysozyme, alkaline phosphatase activity, and percent neutrophils.O₃ effects not modified byT_a included increases in residualvolume and lavageable potassium, glucose, urea, and ascorbic acid.There was a progressive decrease in lavageable uric acid with exposureat 34°C. Most effects were attenuated during the 5 exposure daysand/or returned to normal levels after 7 air recovery days,regardless of prior O₃ exposure orT_a. It is possible thatT_a-induced changes in metabolic rate may have altered ventilation and, therefore, theO₃ doses among rats exposed at thethree different T_a levels.