The development of Puccinia hordei on barley cv. Zephyr

Germination of uredospores of Puccinia hordei was similar on cover-slips and on the first leaves of barley seedlings (cv. Zephyr) at 100 % r.h. over the range 5–25 °C, being greatest at 20 °C. At 15, 20 and 25 °C maximum germination was attained in 6 h. No uredospores germinated on coverslips in humidities below saturation. The numbers of pustules which subsequently developed on plants incubated at 5, 10, 15 or 18 °C and 100 % r.h. for varying periods up to 24 h, were directly related to rise in temperature and length of incubation. The time from inoculation to eruption of pustules (generation time) was 6 days at 25 °C, 8 days at 20 °C, 10 days at 15 °C, 15 days at 10 °C and 60 days at 5 °C. Pustule production on inoculated plants which had been kept at 5 °C was rapidly accelerated when they were transferred to 20 °C. Data obtained at constant temperatures were used to predict generation times of the fungus in the field. The productivity of pustules, determined as weight of uredospores, was examined at 10, 15 and 20 °C. Significantly more spores were produced at 15 than at 10 °C and most were produced at 20 °C. The results are discussed in relation to those obtained by other workers and to the development of brown rust in the field.     

Effects of temperature,irradiance, and daylength on the marine diatom leptocylindrus danicus cleve. I. Photosynthesis and cellular composition

Rates of ¹⁴C uptake and cellular composition of C, N, and Chl a in the marine diatom Leptocylindrus danicus Cleve were measured in axenic batch culture under 49 combinations of temperature (5, 10, 15, 20 °C), daylength (15: 9, 12: 12, 9: 15 LD), and irradiance (at least four irradiances per daylength). ¹⁴C uptake exhibited a temperature-dependent daylength effect. Similar P-I curves characterized cells grown under 15: 9 and 12: 12 LD; P_max values were 17.2, 11.2, 4.3, and 1.8 pg C. pg Chl a^?1. h^?1 at 20, 15, 10, and 5°C, respectively. Under 9:15 LD at 20 and 15°C, the lightsaturated photosynthetic rate was ≈50% that in cells grown under longer daylengths. ¹⁴C uptake was independent of daylength at 10 and 5°C. The initial slope, a, of cells grown under long daylengths increased by five-fold between 5 and 20 °C. α values of cells grown under 9: 15 LD at 15 and 20 °C were depressed relative to longer daylengths. Chl a was inversely related to irradiance, and increased with temperature from 10 to 20 °C, whereas cell carbon and nitrogen showed a similar temperature dependence but was not influenced by irradiance or daylength. The C : N ratio and cell volume were independent of temperature, irradiance, and daylength. Both the C : Chl a and N : Chl a ratios increased with irradiance by greater amounts at lower temperatures.     

OLISTHODISCUS LUTEUS (CHRYSOPHYCEAE) I. EFFECTS OF SALINITY AND TEMPERATURE ON GROWTH. MOTILITY AND SURVIVALS1, 2

The effect of salinity and temperature on Olisthodiscus luteus Carter has been examined to across the relative importance of these factory on dynamics of natural population. A salinity range 2–50% was observed with increased tolerance to low salinity (<5%.) at higher temperature (20–30°C). Slinities at 4–5%. Had densities of 10³ cells/ml^?1, and growth >0.5 division day^?1 at temperature of 15–30°C higher salinities (5–50%.) variable but distinct optima for density, growth and motility were observed 5, 10 and 30°C. Density and motility showed no clear optima from 10–10%.15–25°C where maximum growth rates >1.0 division/day^?1 were common. Temperature increased from (0.5–1.9 division. Day^?1) and increases of three orders of magnitude (10^2?10³) for maximum densities. Temperature optima 20°C for growth 5–35%. And 25°C for >40%. were observed. The implications of these findings to natural populations of O. luleus are discussed.     

Development,Reproduction and Growth Pattern of two Coexisting,Pond Dwelling Cladocerans

Laboratory investigations on life history parameters of 2 coexisting cladocerans (Daphnia obtusa. Moina brachiata) from a nearly temporary pond in South Germany revealed that the species have different temperature tolerances and temperature optima. D. obtusa experienced the highest reproductive success at 15 and 20 °C and was able to survive and to reproduce at 2 °C but died at 30 °C. The reproductive success of M. brachiata was highest at 25 and 30 °C and the species could not withstand temperatures <15 °C and ≥35 °C. At temperatures between approximately 20 and 25 °C, where both cladocerans coexisted in nature, M. brachiata showed a faster population growth due to its approximately twofold higher egg production rates (10–12 eggs female⁻¹ day⁻¹ compared to approximately 5 eggs female⁻¹ day⁻¹ in D. obtusa) and its shorter juvenile development (3.3 and 2.4 days compared to 6.3 and 5.3 days in D. obtusa); M. brachiata needs generally only 3 molts to reach maturity while D. obtusa requires 5–6 molts.     

Effects of temperature on biology and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae)

The development, survivorship, longevity, reproduction, and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama were evaluated at 10°C, 15°C, 20°C, 25°C, 28°C, 30°C and 33°C. The populations reared at 10°C and 33°C failed to develop. Between 15°C and 30°C, mean developmental period from egg to adult varied from 49.3 days at 15°C to 14.1 days at 28°C. The low‐temperature developmental thresholds for 1st through 5th instars were estimated at 11.7°C, 10.7°C, 10.1°C, 10.5°C and 10.9°C, respectively. A modified Logan model was used to describe the relationship between developmental rate and temperature. The survival of the 3rd through 5th nymphal instars at 15–28°C was essentially the same. The mean longevity of females increased with decreasing temperature within 15–30°C. The maximal longevity of individual females was recorded 117, 60, 56, 52 and 51 days at 15°C, 20°C, 25°C, 28°C and 30°C, respectively. The average number of eggs produced per female significantly increased with increasing temperature and reached a maximum of 748.3 eggs at 28°C (P<0.001). The population reared at 28°C had the highest intrinsic rate of increased (0.199) and net reproductive rate (292.2); and the shortest population doubling time (3.5 days) and mean generation time (28.6 days) compared with populations reared at 15–25°C. The optimum range of temperatures for D. citri population growth was 25–28°C.     

Effects of light, temperature and water stress on germination of Artemisia sphaerocephala

Artemisia sphaerocephala is widely used for vegetation rehabilitation, but its germination is very low after air seeding of achenes. We explored effects of light, temperature and water stress on germination. Results show that both final percent germination and germination rate were increased by temperature increment, with the highest values occurring at 15: 25°C (night: day) in dark and 20: 30°C under light. Light inhibited germination, especially at lower alternating temperatures (5: 15°C and 10: 20°C). The alternating temperature window for germination was slightly narrower under light than in dark, and germination was slower under light than in dark across the temperature range. Achenes incubated in the dark and at constant temperatures had over 80% germination at 10 to 25°C, with an optimum at 20°C. Under dark and 25μmol m^‐2 s^‐1 light flux density at 10: 20°C, final percent germination was over 94%, but if the light flux density was increased to 100 and 400 μmol m^‐2 s^‐1, final percent germination was significantly lower (64% and 38% respectively). However, achenes could keep their germination capacity for a long time (over 50 days) and germinate well after going back to the dark. Germination was also lower under water stress and few achenes germinated at ‐1.4 MPa. This was more pronounced at high and low temperatures. Given these findings and the prevailing climatic characteristics, the most suitable time for air seeding of achenes may be mid‐May.     

Comportamento Alla Germinazione Delle Cariossidi Delle Linee Primaverile e Invernale del Triticum Esaploide «Denti de Cani»

Abstract

The germination of spring and winter wheat lines of exaploid Triticum « Denti de Cani ». — The dormancy in the seeds of two lines of Triticum « Denti de Cani » (which is spontaneous in Sardinia), one with solid stem (CP line), a spring line, the other with hollow stem (CV line), an winter line, has been studied. Germination was carried out in the dark, in Petri dishes at the constant temperatures of 5°, 10°, 20°, 23°, 26°, 30° and 35°C, using full ripe seeds, and seeds in different stages of after-ripening up to one year of age. The increase in % germination, for increasing temperatures above 5°C, is clearly conditioned by the progress of after-ripening in the seeds. In fact it was seen that, in general for the two lines, percentages over 50% of seeds germinated at 3 days were reached: at 10° and 20° after 15 days from the full ripening; at 23°C after 30 days; at 26°C after 50 days; at 30°C after about 100 days and at 35°C only after about 4–5 months from the harvest. During the experiment at 5°C it was observed that, during the first year of life of seeds and especially in the CP line, this temperature produces a clear slowing down in germinations after first year from the ripening, only the CV seeds — not the CP which remain very much inhibited — reach germination values over 50% at 3 days. It has also been demonstrated that the CV are more sensitive than the CP, in the first initial period of after-ripening (15 and 30 days), to the non-inhibiting activity of low temperatures (5° and 10°C) and that, between these, the 10°C temperature promotes the germination more clearly than the 5°C temperature. The results obtained have shown that the dormancy wears off in the spring CP-line much more slowly than in the winter CV-line. The CP-seeds remain in a relative dormancy condition for a long time, which causes a significative delay in germination, up to 100 days from the full ripening stage.     

Life history parameters for Nesidiocoris tenuis (Reuter) (Het., Miridae) under different temperature regimes

The development time for eggs and nymphs and female fertility were determined for Nesidiocoris tenuis Reuter (Het., Miridae: Dicyphini) at 15, 20, 25, 30, 35 and 40 ± 1°C, using tomato, Solanum esculentum (Miller), as substrate and eggs of Ephestia kuehniella Zeller as substitute prey. At 40°C, N. tenuis was unable to develop and barely reproduced. Egg development ranged from 30.8 days at 15°C to 6.3 days at 35°C. The cumulative thermal requirements for the eggs were 148.6 degree days (°d) and the lower thermal threshold, 10.3°C. The duration of the nymphal instar decreased from 55.9 days at 15°C to 8.6 days at 35°C. The thermal constant for the nymphs was 182.3 °d and the lower thermal threshold 11.7°C. No nymphs survived at 40°C, and the highest mortalities were at extreme temperatures (15 and 35°C). Female and male weights were influenced significantly by temperature. The fertility of N. tenuis females was reduced greatly at 15 and 40°C. The highest fertility during an observation period of 18 days following female emergence (79.5–60.0 nymphs per female) was within the temperature range of 20 to 35°C. Fertility was related directly to female weight and temperature (r² = 0.932). Based on development, reproduction data and thermal requirements, the optimum temperature range for N. tenuis was established as being between 20 and 30°C. Overall, N. tenuis is the most thermophilous of all dicyphines from vegetable crops in the Mediterranean area studied so far.     

Alternating temperatures affect life table parameters of Phytoseiulus persimilis, Neoseiulus californicus (Acari: Phytoseiidae) and their prey Tetranychus urticae (Acari: Tetranychidae)

Increasing energy costs force glasshouse growers to switch to energy saving strategies. In the temperature integration approach, considerable daily temperature variations are allowed, which not only have an important influence on plant growth but also on the development rate of arthropods in the crop. Therefore, we examined the influence of two constant temperature regimes (15 °C/15 °C and 20 °C/20 °C) and one alternating temperature regime (20 °C/5 °C, with an average of 15 °C) on life table parameters of Phytoseiulus persimilis and Neoseiulus californicus and their target pest, the two-spotted spider mite Tetranychus urticae at a 16:8 (L:D) h photoperiod and 65 ± 5 % RH. For females of both predatory mites the alternating temperature regime resulted in a 25–30 % shorter developmental time as compared to the corresponding mean constant temperature regime of 15 °C/15 °C. The immature development of female spider mites was prolonged for 7 days at 15 °C/15 °C as compared to 20 °C/5 °C. With a daytime temperature of 20 °C, no differences in lifetime fecundity were observed between a nighttime temperature of 20 and 5 °C for P. persimilis and T. urticae. The two latter species did show a higher lifetime fecundity at 20 °C/5 °C than at 15 °C/15 °C, and their daily fecundity at the alternating regime was about 30 % higher than at the corresponding mean constant temperature. P. persimilis and T. urticae showed no differences in sex ratio between the three temperature regimes, whereas the proportion of N. californicus females at 15 °C/15 °C (54.2 %) was significantly lower than that at 20 °C/5 °C (69.4 %) and 20 °C/20 °C (67.2 %). Intrinsic rates of increase were higher at the alternating temperature than at the corresponding mean constant temperature for both pest and predators. Our results indicate that thermal responses of the studied phytoseiid predators to alternating temperature regimes used in energy saving strategies in glasshouse crops may have consequences for their efficacy in biological control programs.     

Viruses Associated with a Mosaic Disease of Crotalaria juncea in Nigeria

Cowpea mosaic virus was one of the viruses isolated from Crotalaria juncea showing mosaic, distortion and puckering symptoms. The virus induced local necrotic lesions in Canavalia ensiformis, Cassia occidentalis, Nicotiana debneyi, N. occidentalis, N. repanda and N. sylvestris and some cultivars of Phaseolus vulgaris 4–6 days after inoculation. It induced local chlorotic spots, which later became necrotic, as well as systemic chlorotic spots, vein chlorosis, distortionand puckering in Chenopodium amaranticolor. Sap from systemically infected cowpea cv. ‘C20-55’was infective after dilution to 10^?5 but not 10^?6, after 10 min at 65°C but not 70°C, or after 4 days, but not 5 days, at a room temperature of 15–25°C. Infectious virus was recovered from fresh reproductive tissues of infected cowpea cvs ‘C20-55’and ‘Ife Brown’ plants but not after dehydration.     

Host and environmental effects on the infection of maize by Puccinia sorghi. I. Prepenetration development and peneration

Germination of urediniospores of Puccinia sorghi on leafves and on ager was sminilar over the range 5–25°C, being greatest at 15°C, At this temperature, maximum germination was attained withing 5 h. Germination on cover slips started at around 99% r. h. and increased with of humidity. Urediniospore germination was not affected by leaf age. In generalk, proportionally more spores germinated on the abaxial than on the adaxial surface. Maximum germination was observed on the abxial surface of the tip portion of the leaf. The optimum temperature for infection structure formation was about 15°C, A munimum period of 3–4 h was required for the initiation of infection. Increase in appressorium and sub-stomatal vesicle formation with increase in dew perio ws observed, with the maxima being attained at about 24 h after inculation.     

Temperature-correlated force and structure development in elastomeric polypeptides: the Ile1 analog of the polypentapeptide of elastin

The Ile¹ analog of the polypentapeptide of elastin, (L · Ile¹-L · Pro²-Gly³-L · Val⁴-Gly⁵)_n, abbreviated as Ile¹-PPP, was synthesized with n > 100 to determine the effect of the increased hydrophobicity of the pentamer resulting from Val¹ replacement by Ile¹ on the previously characterized inverse temperature transition of the polypentapeptide of elastin (PPP). Ile¹-PPP, dissolved in water at 4°C, was found to aggregate, forming a viscoelastic coacervate on raising the temperature. The onset of aggregation was 8°C for Ile¹-PPP, as compared to 24°C for PPP. Characterization by CD demonstrated an increase in intramolecular order on raising the temperature from 8°C to 25°C, and demonstrated similar conformations for PPP and Ile¹-PPP before and after their respective transitions. The CD-characterized transition also occurred at a temperature some 15°C lower than that of PPP. By means of 20-Mrad γ-irradiation cross-linking of the Ile¹-PPP coacervate, an elastomeric matrix was formed with an elastic modulus, similar to that of 20-Mrad cross-linked PPP. The temperature dependence of elastomeric force of cross-linked Ile¹-PPP showed an abrupt increase from essentially zero at 8°C to three-quarters of full force at 10°C and essentially full force by 20–25°C. This development of elastomeric force for the more hydrophobic Ile¹-PPP matrix, which parallels the increase in intramolecular order characterized by the CD studies, also occurs at a temperature some 15°C lower than that for the PPP matrix. Thus, in these elastomeric polypeptides, development of elastomeric force is coupled to an inverse temperature transition, the temperature of which depends inversely on the hydrophobicity of the constituent pentamer. It appears that a series of elastomeric polypeptide biomaterials are possible in which the temperature over which elastomeric force develops can be varied.     

Effects of low temperature on diapause termination and body colour change in adults of a stink bug, Plautia stali

Abstract. Diapause adults of Plautia stali Scott maintained at 20°C under short day conditions (LD 12:12 h) were exposed to four temperatures of 5–20°C to examine the effect on diapause development which was assessed in terms of oviposition. Diapause adults kept at 20°C under short day conditions changed their body colour gradually from brown to green and started egg laying after a prolonged preoviposition period. Those transferred to either 10 or 15°C also showed colour change but did not lay eggs. Bugs exposed to 5°C underwent neither body colour change nor oviposition and died more rapidly than those kept at higher temperatures. When 30-day-old diapause adults were chilled at 5, 10 or 15°C for 30 or 60 days and returned to 20°C and long day conditions (LD 16:8 h), the preoviposition period varied primarily depending on the chilling, but not on the temperature. On the other hand, when 60day-old diapause adults chilled for 30 days were observed at 20°C and long day conditions, their preoviposition period tended to be longer as the chilling temperature was lower In this case, a temperature of 10°C appeared to intensify diapause. Therefore, the effect of chilling on diapause development varied depending on the age at which insects were chilled. When chilled bugs were transferred to short day conditions at 20°C, most females failed to lay any eggs and some turned green, then after a while, some green bugs changed to brown again. These results indicate that bugs remained sensitive to short day conditions even after a 60-day chilling at 10 or 15°C.     

Post-harvest age-induced seed dormancy of Acer ginnala and its alleviation by growth regulator and low temperature treatments

One-month-old fruits of Acer ginnala with winged pericarp attached gave 44% germination and this was not increased by cold treatment at 4°C for 0, 10, 20, or 30 days, gibberellic acid treatment at 0, 1, 10, 100 or 1000 mg litre^-1, or ethephon treatment at 0, 2, 20, 200 or 2000 mg litre^-1. After 6 months of storage at 20–25 °C, germination of untreated fruits fell to 5% but could be restored to that of 1-month-old fruits by incubation at 4 °C for 30 days. After 9 months storage, no germination occurred in untreated fruits. Cold treatment (30 days at 4 °C partially restored germination (26%). Treatment with either gibberellic acid (1000 mg litre^-1) and 30 days at 4 °C (40%) or ethephon (100 mg litre^-] and 30 days at 4 °C improved germination (69%). The combination of all three treatments, i.e. 100 mg litre^-1 gibberellic acid, 100 mg litre^-1 ethephon and 30 days at 4 °C, optimised germination (86%). Thus, dormancy of A. ginnala developed during storage but could be reversed by a combination of treatment with low temperature and growth regulators. The highest germination (86%) was achieved after low temperature and growth regulator treatment of stored fruit.     

Thermal responses in the citrus fruit fly,Dacus tsuneonis: evidence for a pupal diapause

Thermal responses controlling pupariation and adult eclosion in a citrus fruit fly,Dacus tsuneonis (Miyake), were studied to understand the winter biology of this species. When mature larvae were exposed to various temperature conditions, the highest percentage of pupariation was obtained at 15 °C, although the variance at this temperature was greater than at 20 °C or 25 °C. Pupariation occurred most rapidly at 20 °C and an alternating temperature with a mean of 15 °C. At constant 15 °C, pupae failed to emerge as adults. Pupae were characterized by a reduced respiration rate, which is typical of a diapausing pupa. When insects were stored at different temperatures for 45 days after pupariation, and then transferred to 25 °C, adult eclosion occurred earlier when the initial temperature was 10 °C than when it was 5 °C or 15 °C. Adult eclosion occurred most synchronously and pupal mortality was lowest when insects were stored at 15 °C for 90 days before incubation at 25 °C. These results strongly suggest thatD. tsuneonis enters a pupal diapause.     

Cold hardiness and sugar content in photo‐insensitive individuals of the cotton bollworm Helicoverpa armigera

Abstract A proportion of Helicoverpa armigera collected from fields in Okayama Prefecture (Western Japan; 34.6°N, 134.1°E) does not enter diapause when reared under a short days at 20 °C during the larval stages. However, diapause in such photo‐insensitive individuals can be induced when they are reared at moderately low temperatures, such as 15 °C, regardless of photoperiod. To determine whether such photo‐insensitive individuals can survive overwintering in fields, the present study compares the cold hardiness and sugar content between nondiapausing and diapausing pupae of photo‐insensitive individuals selected over several generations at 20 °C under a short day photoperiod (LD 10 : 14 h). Diapausing and nondiapausing pupae are obtained under the short days by rearing at 15 and 20 °C, respectively, during larval and pupal stages. These pupae are stepwise acclimated at a reduction of 5 °C every 5 days to 0 °C. Maximum survival periods of nondiapausing and diapausing pupae at 0 °C are approximately 30 and 90 days, respectively. Trehalose content in diapausing pupae increases, reaches a maximum level (1.95 mg 100 mg^?1 in males and 2.1 mg 100 mg^?1 in females) 28 days after exposure to 0 °C and then decreases. On the other hand, glucose content in diapausing pupae increases (maximum level: 0.32 mg 100 mg^?1 in males and 0.21 mg 100 mg^?1 in females) with decreasing trehalose content 42 days after exposure to 0°C. The decrease in trehalose content and the increase in glucose content may be linked to termination of diapause in H. armigera. These results suggest that, in Japan, the photo‐insensitive individuals can only survive in the mild winters of southern regions, and not in the severe winters of northern regions.     

Kinetin-Mediated Prolongation of Viability in Recalcitrant Sal (Shorea robusta Gaertn. f.) Seeds at Low Temperature: Role of Kinetin in Delaying Membrane Deterioration during Desiccation-Induced Injury

The effects of kinetin (6-furfurylaminopurine) on viability during storage of recalcitrant sal (Shorea robusta Gaertn. f.) seeds at low temperature (15°C) were investigated. The freshly mature sal seeds showed an absolute loss of viability within 6–7 dah (days after harvest) when stored at ambient or at 15°C (control). Storage of these seeds at 15°C after kinetin (10 ppm) treatment prolonged the viability period up to 35 days with 20% germination. The kinetin-treated seeds exhibited 100% germination up to 10 days compared with 3 days in controls. Measurements of leachate conductivity, ·O⁻ ₂ and lipid peroxidation registered gradual increases from 0 dah onward to 35 dah with significantly low levels compared with controls. On the other hand, an enormous increase in superoxide dismutase activity was discernible for a longer duration (0–35 dah) in kinetin-treated seeds than in control seeds where it remained for 3 dah. The role of kinetin in prolonging seed viability by reducing the loss of leachates, lipid peroxidation, ·O⁻ ₂, and enhancing of superoxide dismutase is discussed. Received October 7, 1997; accepted January 27, 1998     

Life table and heat tolerance of Acyrthosiphon pisum (Hemiptera: Aphididae) in subtropical Taiwan

The effect of temperature on the life table of Acyrthosiphon pisum reared on Pisum sativum was evaluated under laboratory conditions using temperatures of 10, 15, 20, 25, 30, and 35°C. The development time of juvenile A. pisum decreased with increasing temperature (from 21.3 days at 10°C to 4.7 days at 35°C). Adult longevity also decreased with increasing temperature (from 53.2 days at 10°C to 2.3 days at 35°C). Interestingly, 70% and 25% of A. pisum nymphs reared at 30°C and 35°C, respectively, successfully developed into adults. These temperatures have previously been considered unsuitable for A. pisum development. However, adult aphids reared at 30°C and 35°C failed to reproduce. Linear regression analysis revealed that the lower development threshold of A. pisum was 153.1 degree‐days above 1.9°C. Maximal average reproductive capability was observed at 10°C for A. pisum adults, with each adult producing more than 120 nymphs. The intrinsic rate of increase (r_m) of A. pisum increased from 0.124/day at 10°C to 0.337/day at 25°C, whereas opposite trends were observed for the net reproductive rate (R₀) and the mean generation time (GT). At 20°C and 25°C, the intrinsic rate of increase of A. pisum was significantly higher than at 10°C and 15°C (P < 0.0001), indicating that 20°C and 25°C are within the optimal range for the growth of A. pisum, and that 30°C is beyond the upper threshold limit for reproduction, which involves a temperature range that is narrower than that of the survival range (upper limit is unknown, but above 35°C).     

The effect of seed conditioning,short-term heat shock and salicylic,jasmonic acid or brasinolide on sunflower (Helianthus annuus L.) chilling resistance and polysome formation

The aim of this study was to develop the method for increasing resistance of sunflower seedlings ‘Wielkopolski’ to chilling. Seeds were conditioned at 25 °C for 2 days in water to 15, 20 and 25 % moisture content or in salicylic or jasmonic acid in concentration of 10^?2; 10^?3 and 10^?4 M or brassinolide in concentration of 10^?6; 10^?8 and 10^?10–15 % moisture content. After 2 days of incubation the conditioned seeds were heat shocked at 45 °C for 0, 30, 60, 120 and 240 min and 5 mm seedlings were exposed to chilling at 0 °C for 21 days. The effectiveness of the methods was assessed by evaluation of roots growth in Phytotoxkit Microbiotest, changes in the activity of dehydrogenases, the integrity of the cytoplasmic membrane and formation of polysomes after seedling were returned to 25 °C for 72 h. Seeds were conditioned at 25 °C for 2 days in water to 15 % moisture content and then heat shocked at 45 °C for 2 h decreased chilling injury of seedlings expressed by subsequent growth of the roots, electrolyte leakage, dehydrogenases activity and polysomes formation. Application of heat shock of 45 °C for 2 h during seed conditioning additionally provided seedling protection against subsequent chilling conditions. Brasinolide, salicylic acid or jasmonic acid applied during seeds conditioning exhibited further beneficial effect on seedling resistance to chilling. The most pronounced effect was obtained due to seed conditioning to 15 % moisture content in solutions of brassinolide in concentration of 10^?8 M. After 2 days of imbibition treated in this way seeds were exposed to heat shock at 45 °C for 2 h. The role of physiological events in improvement of sunflower chilling tolerance are discussed.     

Glucose metabolism in the hypothermic perfused rat heart.

Although hypothermic whole organ perfusion is widely used in attempts to preserve organs for transplantation and to preserve the myocardium during cardiac surgery, little is known about substrate metabolism during hypothermia. A knowledge of metabolism utilization during hypothermic whole organ perfusion might allow optimal substrate choice for preservation of energy stores and functional capacity. Separate groups of hearts from fed rats were perfused 30 minutes with Krebs Henseleit bicarbonate buffer containing 5mM glucose-U-¹⁴C, at 37°, 25°, 20°, 15° and 10°C. From 37° to 15°C, heart rate decreased 90% and coronary flow decreased 25%. Glucose uptake decreased 5 fold from 37° to 10°C while ¹⁴CO₂ and lactate production decreased 50 fold and 28 fold, respectively. Myocardial glycogen was stable until 10°C at which point increased glycogenolysis occured. The incorporation of ¹⁴C in glycogen was stable at 37°, 30° and 25° but decreased progressively with lower temperatures. The percent recovery of glucose as ¹⁴CO₂, lactate and ¹⁴C in glycogen decreased from 73% at 37° at 10°C. Our studies indicate that metabolism of glucose is greatly reduced but significant above 15°C.