Effect of Simulated Soil Solarization and Organic Amendments on Fusarium Wilt of Rocket and Basil Under Controlled Conditions

Pot trials were carried out under controlled conditions to evaluate the effectiveness against Fusarium wilt of rocket (Fusarium oxysporum f.sp. conglutinans) and basil (F. oxysporum f.sp. basilici) of soil amendments based on a patented formulation of Brassica carinata defatted seed meal and compost, combined or not with a simulation of soil solarization. The soil solarization treatment was carried out in a growth chamber by heating the soil for 7 and 14 days at optimal (55–52°C for 6 h, 50–48°C for 8 h and 47–45°C for 10 h/day) and sub‐optimal (50–48°C for 6 h, 45–43°C for 8 h and 40–38°C for 10 h/day) temperatures similar to those observed in summer in solarized soil in greenhouses in Northern Italy. Two subsequent cycles of plant cultivation were carried out in the same soil. Even at sub‐optimal temperature regimes, 7 days of thermal treatment provided very valuable results in terms of disease control on both rocket and basil. In general, the thermal treatment was more effective against F. oxysporum f.sp. basilici than against F. oxysporum f.sp. conglutinans. Control of Fusarium wilt of rocket is improved with 14 days of thermal treatment. The combination of organic amendments with a short period of soil solarization (7 or 14 days), although not providing any improvement to the level of disease management, did significantly increase biomass and positively affected yield.     

Nitrogen utilization by Typha latifolia L. as affected by temperature and rate of nitrogen application

Greenhouse and growth chamber studies were conducted to evaluate growth and N utilization by Typha latifolia L. in flooded organic soil under varying temperatures and rates of N additions. Elevation of temperature from 10 to 25°C increased shoot biomass yields by 275%. Root biomass yields were lowest at 10°C and increased linearly as a function of temperature. Shoot/root ratios were low (0.72–0.82) at lower temperatures (10–15°C) and ratios increased by about three times at higher temperatures (20–30°C). Biomass yields were increased by addition of N fertilizers, while the shoot/root ratios were directly related to plant-available N present in the soil.Fertilizer ¹⁵N uptake (expressed as % of applied N) by the whole plant was 5.3% at 10°C, 37.5% at 20°C and at 30°C decreased to 20.8%. Fertilizer N accumulation in shoots was 2.1–29.8% of applied N, while roots accumulated 3.2–7.7%. Under greenhouse conditions, N uptake by T. latifolia was found to increase with increased rate of N application. Fertilizer N uptake by both shoots and roots was in the range of 61–77%. Plants cultured in growth chambers were affected by low light conditions resulting in poor growth and low fertilizer ¹⁵N uptake, as compared to plants grown under greenhouse conditions. Added fertilizer N was the major source of N during the early part of the growing season, while soil organic N was the major and perhaps the sole source of N during the latter part of the growing season.     

Growth responses of Typha orientalis presl to controlled temperatures and photoperiods

Experiments are described in which seedlings of Typha orientalis Presls were grown for up to 6 months under precise conditions of temperature and photoperiod; photosynthesis was by natural daylight and did not vary between treatments. Variable treatments were imposed either from the seedling stage or on large plants raised under constant conditions.In general, total dry matter production increased as photoperiod increased from 8 to 16 h and also as day or night temperature increased, maximum production occurring when there was a warm day (30 or 27°C) and a small temperature drop (to 22°C) at night. The distribution of dry matter was also markedly affected by the imposed variables, leaf growth being favoured by high temperatures (to 30°C) and long photoperiods, and production of roots and rhizomes by low temperatures (to 10°C) and short photoperiods. None of the treatments resulted in floral initiation. The results are considered in relation to growth in the natural habitat.     

Temperature Dependence of Methane Production in Tropical Rice Soils

Although CH 4 production is sensitive to temperature, it is not clear how temperature controls CH 4 production directly versus the production of organic substrates that methanogens convert into CH 4 . Therefore, this study was done to better understand how CH 4 production in rice paddy soil responded to temperature when the process was not limited by the availability of substrates. In a laboratory-incubation study using three Indian rice soils under flooded conditions, the effect of temperature on CH 4 production was examined. CH 4 production in acid sulphate, laterite, and alluvial soil samples under flooded conditions distinctly increased with increase in temperature from 15°C to 35°C. Laterite and acid sulphate soils produced distinctly less CH 4 than alluvial soils. CO 2 production increased with increase in temperature in all the soils. The readily mineralizable carbon C and Fe 2+ contents in soils were least at 15°C and highest at 35°C, irrespective of soil type. Likewise, a significant correlation existed between microbial population (methanogens and sulphate reducers) and CH 4 production. Comparing the temperature coefficients ( Q 10 ) for methane production within each soil type at low (15°C-25°C) and medium (25°C-35°C) temperature intervals revealed that these values were not uniform for both alluvial and laterite soils. But acid sulphate soil had Q 10 values that were near 2 at both temperature intervals. When these soil samples were amended with substrates (acetate, H 2 -CO 2 , and rice straw), there were stimulatory effects on methane production rates and consequently on the Q 10 values. The pattern of temperature coefficients was characteristic of the soil type and the nature of substrates used for amendment.     

Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short‐term temperature dependencies of Antarctic soil bacterial community growth rates, using the leucine incorporation technique, in order to predict future changes in temperature sensitivity of resident soil bacterial communities. Soil samples were collected along a climate gradient consisting of locations on the Antarctic Peninsula (Anchorage Island, 67 °34′S, 68 °08′W), Signy Island (60 °43′S, 45 °38′W) and the Falkland Islands (51 °76′S 59 °03′W). At each location, experimental plots were subjected to warming by open top chambers (OTCs) and paired with control plots on vegetated and fell‐field habitats. The bacterial communities were adapted to the mean annual temperature of their environment, as shown by a significant correlation between the mean annual soil temperature and the minimum temperature for bacterial growth (T_min). Every 1 °C rise in soil temperature was estimated to increase T_min by 0.24–0.38 °C. The optimum temperature for bacterial growth varied less and did not have as clear a relationship with soil temperature. Temperature sensitivity, indicated by Q₁₀ values, increased with mean annual soil temperature, suggesting that bacterial communities from colder regions were less temperature sensitive than those from the warmer regions. The OTC warming (generally <1 °C temperature increases) over 3 years had no effects on temperature relationship of the soil bacterial community. We estimate that the predicted temperature increase of 2.6 °C for the Antarctic Peninsula would increase T_min by 0.6–1 °C and Q₁₀ (0–10 °C) by 0.5 units.     

Temperature and Leaf Wetness Effects on Infection of Sugarcane by Puccinia melanocephala

Brown rust epidemics in sugarcane, caused by Puccinia melanocephala, vary in severity between seasons. To improve the understanding of disease epidemiology, the effects of leaf wetness, temperature and their interaction on infection of sugarcane by the pathogen were studied under controlled conditions. Disease severity was low at 15 and 31°C regardless of leaf wetness duration. No infection occurred with a 4‐h leaf wetness period. Increasing leaf wetness duration from 7 to 13 h lowered the temperature required for disease onset from 21 to 17°C. More infection occurred with 13 compared to 10 h of leaf wetness at 17°C, and severity decreased for all leaf wetness periods at 29 compared to 27°C. Postinfection suboptimal low and high temperatures increased the time required for lesion development and high temperatures decreased maximum disease severity. The observed effects of leaf wetness and temperature on infection by P. melanocephala could help explain the initiation, rate of increase and decline of brown rust epidemics in the field.     

The Effect of Temperature on the Bioventing of Soil Contaminated with Toluene and Decane

The effect of temperature on evaporation and biodegradation rates during soil bioventing (SBV) was studied for a mixture of toluene and decane in bench-scale soil columns at a continuous air flow and consecutively at two different flow rates. The effect of temperature on SBV was monitored by GC headspace analysis of contaminant, CO₂ and O₂ concentrations in the soil gas over time. Separation of evaporation and biodegradation processes into three different phases based on their rates was used together with Q₁₀ and E₁₀ (values that give the factor by which biodegradation and evaporation rates increase when the temperature is raised by 10 degrees) to compare quantitatively the removal kinetics at 10 and 20°C. Adsorption of toluene and decane onto soil (a phase partitioning process) at 20 and 10°C was described with linear Freundlich isotherms. A temperature decrease from 20 to 10°C resulted in an increase of soil-air partitioning coefficients by a factor of 1.8 and of 2.1 for toluene and decane, respectively. The mean Q₁₀ value for the biodegradation of toluene was found to be 2.2 for a temperature rise from 10 to 20°C. A toluene content in the soil gas above 75% of the saturation concentration inhibited biodegradation at both temperatures. The SBV efficiency was dependent on temperature with respect to remediation time. SBV at 20°C resulted in a 99.8% and a 98.7% reduction of toluene and decane initial concentrations, respectively. To reach similar results at 10°C, about 1.6 times as much time and 1.4 times as much air were required; however, at both temperatures the total amounts of biodegraded hydrocarbons were approximately the same. The evaporation-to-biodegradation ratios at 20°C were 82.5:17.5 for toluene and 16:84 for decane, whereas at 10 °C they were 71:29 and 2:98, respectively. A comparison of Q₁₀ values showed that, except during the initial phase of SBV, only a modest decrease in biodegradation rates should be expected after a decrease in temperature from 20 to 10°C. Flow rate reduction had a significant impact on the toluene evaporation rate at a higher temperature, whereas for decane this rate was only slightly affected by temperature. In contrast to decane, the ratio between toluene vapor pressures at 20 and 10°C may be used to predict the removal of toluene by evaporation during the above-mentioned phases of SBV, when evaporation is important.     

Heat induced infertility of boars: The inter-relationship between depressed sperm output and fertility and an estimation of the critical air temperature above which sperm output is impaired

Eight groups of Large-White gilts were each inseminated with different numbers of normal motile sperm, in the range 0.28–7.0 × 10⁹. A significant (P < 0.05) relationship between conception rate and the number of motile sperm inseminated was shown. This relationship can be used to equate output of motile sperm with levels of fertility of boars. The optimal number of motile sperm for conception following intra-cervical insemination was near 5 × 10⁹ and the threshold number, below which animals did not conceive, was c. 4 × 10⁸.In a second experiment, three Large-White boars were subjected to graded thermal treatment (air temperature was increased by 1°C per day for 20 days, from a basal level of 20°C to a maximal level of 40°C) and responses of ejaculate and other physiological characteristics were monitored. Scrotal surface temperature, respiration rate and rectal temperature increased (P < 0.05) beyond basal levels at air temperatures of 30°C, 33°C and 35°C, respectively. Motility of sperm in ejaculates decreased when air temperature reached 30°C and this response was presumed to reflect hyperthermia in epididymal tissues, consistent with increasing scrotal surface temperature at this same air temperature. Motility fell below a pre-treatment level of about 93%, to 19% (P < 0.05), 3 weeks after heating. Volumes of seminal plasma and gel in ejaculates were also lower (P < 0.05) following heating. Changes in daily sperm production were minor and, as a result, daily motile sperm production levels paralleled changes in motility. Proportions of abnormal types of sperm increased (P < 0.05) to maximal levels in the last week of heating and all returned to pretreatment values 5 weeks later. High proportions of sperm with kinoplasmic droplets appeared in ejaculates collected after heating (P < 0.05), evidence that epididymal cell types in the boar are sensitive to heat.As a result of heat treatment, normal motile sperm production decreased from control levels (1.28 × 10¹⁰·day^?1) to 0.15 × 10¹⁰·day^?1, 3 weeks after heating ceased. However, the results suggest that normal sperm output by Large-White boars can be maintained at air temperatures as high as 29°C.By relating the results of both experiments, it is concluded that fertility of the boars in the second experiment (if mated once daily) would be depressed for about 5 weeks after heat treatment ceased. The findings support many field reports which indicate a contribution of boars to lower conception rates of sows during and immediately following summer and the results can be used in formulating strategies to circumvent this widespread problem.     

Influence of post-flowering temperature on seed development, and subsequent performance of crisp lettuce

Crisp lettuce plants cv. Saladin were grown from the time they started flowering, at 20/10°C (16 h day, 8 h night), 25/15°C and 30/20°C in glasshouses on two occasions in 1985. Yields of seed increased from, on average, 15 g to 27 g and then fell to 20 g per plant with progressive increases in temperature. The number of mature florets per plant increased with temperature but the number of seeds per mature floret was lower at 20/10°C and 30/20°C than at 25/15°C. An increase in temperature reduced mean seed weight by up to 45%, seed volume by 15%, cell numerical volume density (N_v) by 27% and the number of cells per seed by 39%. Percentage seed germination reached a maximum early in seed development at the stage when the pappus appeared through the involucral bracts. Differences in percentage germination and vigour of seeds (slope test) from different temperatures were accounted for largely by the effects on mean seed weight. However, when germinated at 30°C seeds produced at 30/20°C germinated more readily than those produced at 25/15°C or 20/10°C. Seed vigour gradually increased with an increase in the length of storage after harvest, reaching a maximum after 260 days. In general, seeds produced at 25/15°C exhibited a greater variation in numbers of seeds per floret, N_v, seed weight, times of seedling emergence, seedling and mature head weight than seeds produced at lower or higher temperatures.     

A new method to determine the energy saving night temperature for vegetative growth of Phalaenopsis

Knowledge of the energy saving night temperature (i.e. a relatively cool night temperature without affecting photosynthetic activity and physiology) and a better understanding of low night temperature effects on the photosynthetic physiology of Phalaenopsis would improve their production in terms of greenhouse temperature control and energy use. Therefore, Phalaenopsis‘Hercules’ was subjected to day temperatures of 27.5°C and night temperatures of 27.0°C, 24.2°C, 21.2°C, 18.3°C, 15.3°C or 12.3°C in a growth chamber. A new tool for the determination of the energy saving night temperature range was developed based on temperature response curves of leaf net CO₂ exchange, chlorophyll fluorescence, organic acid content and carbohydrate concentrations. The newly developed method was validated during a complete vegetative cultivation in a greenhouse environment with eight Phalaenopsis hybrids (i.e. ‘Boston’, ‘Bristol’, ‘Chalk Dust', ‘Fire Fly’, ‘Lennestadt’, ‘Liverpool’, ‘Precious’, ‘Vivaldi’) and day/night temperature set points of 28/28°C, 29/23°C and 29/17°C. Temperature response curves revealed an overall energy saving night temperature range for nocturnal CO₂ uptake, carbohydrate metabolism, organic acid accumulation and photosystem II (PSII) photochemistry of 17.1°C to 19.9°C for Phalaenopsis‘Hercules’. At the lower end of this energy saving night temperature range, a high malate‐to‐citrate ratio switched towards a low ratio and this transition seemed to alleviate effects of night chilling induced photoinhibition. At night temperatures of 24°C or higher, the degradation of starch, glucose and fructose indicated an increased respiratory CO₂ production. During the greenhouse validation experiment, the differences between the eight Phalaenopsis hybrids with regard to their response to the warm day/cool night temperature regimes were remarkably large. In general, the day/night temperature of 29/17°C led to a significantly lower biomass accumulation and less leaves which were in addition shorter, narrower and smaller in size as compared to the day/night temperature regimes of 28/28°C and 29/23°C. During week 25 of the cultivation period, plants matured and flower initiation steeply increased for all hybrids and in each day/night temperature regime. Before week 25, early spiking was only sufficiently suppressed in the 29/23°C and 29/17°C temperature regimes for three hybrids (‘Boston’, ‘Bristol’ and ‘Lennestadt’) but not in the other five hybrids. Although a considerable biochemical flexibility was demonstrated for Phalaenopsis‘Hercules’, inhibition of flowering after exposure to a combination of warm days and cool nights appeared to be largely hybrid dependent.     

Degradation of moist soil aggregates by rapid temperature rise under low intensity fire

Background and aims

Soil structure degradation by fire is usually attributed to qualitative and quantitative change of organic and inorganic binding agents, especially in high severity burns (>300 °C) that last for prolonged periods (> 1 hour). In contrast, controlled burns are typically managed to be low in intensity and severity. Such burns are considered benign to soil structural stability because organic matter and inorganic binding agents (e.g., gypsum) are relatively stable at such low temperatures. Recent observations at a controlled burn site in the eastern Great Basin (Nevada) showed soil aggregate breakdown found in shrub canopies where soil temperatures briefly exceeded 300 °C as well as interspaces between shrubs, where the temperatures were likely lower than beneath shrubs because of less surface biomass. These alterations cannot be explained in terms of thermal alteration of binding agents. This study was designed to test whether pressure created by rapidly vaporized pore water can cause aggregate breakdown.

Methods

We subjected three different sizes of aggregates (0.25–1, 1–2 and 2–4 mm) of soils derived from the eastern Great Basin burn site as well as from a forest and urban garden in California to rapid and slow (3 °C/min) heating rates. These treatments were conducted at 5 peak temperatures (75, 100, 125, 150 and 175 °C).

Results

Post-burn water stability of the aggregates showed that rapid heating rate caused more pronounced degradation of aggregate stability than slow heating. Moreover, the heating-rate dependent structural degradation increased with peak temperature. For the majority of the aggregates, the effect also increased with initial water content. In all the soils tested, there was no preferential loss of organic matter in the rapid-heating treatment that can explain the observed enhanced breakdown of aggregates.

Conclusions

Our observations indicate that soil structural degradation under low-intensity fire occurs as a result of mechanical stresses extorted by rapidly escaping steam from soil pores under rapid heating rate.     

The Influence of Temperature on Floral Initiation in the Olive

Floral initiation is completely inhibited when the olive is grown in a glasshouse at a minimum temperature of 16°C and a maximum temperature of 27°–30°C but occurs when it is grown at natural winter conditions in California. This study was undertaken to determine more specifically the temperature requirements for flowering and to show the relation of temperature treatment to hud development and floral initiation. Results of experiments performed with trees in containers grown at constant temperatures in controlled environment growth rooms show that the optimum temperature for flowering is 10°–13°C. Either higher (18°C) or lower (4°C) temperatures inhibit flowering completely. Morphological studies show that axis elongation and floral initiation occur in buds during temperature treatment at 10°C and 13°C but fail to occur during 4°C or 18°C treatments, or following these treatments when the temperature is raised to 21°C. When plants were exposed to 13°C for varying durations, it was found that no inflorescences formed after a 7.5 week exposure but that many formed after an 11-week exposure. A subsequent experiment showed that many more inflorescences formed after a 10-week exposure at 13°C than after 9 weeks exposure. Morphological changes in the bud seem to be associated with this increase in flowering affected by duration of treatment.     

The effect of drought stress and temperature on spread of barley yellow dwarf virus (BYDV)

1 The effect of drought stress and temperature on the dispersal of wingless aphids Rhopalosiphum padi (L.) and the pattern of spread of BYDV (barley yellow dwarf virus) within wheat plants in controlled environment chambers was quantified. Combinations of three different drought stress levels, unstressed, moderate and high stress level, and three different temperatures, 5 ± 1 °C, 10 ± 1 °C, and 15 ± 1 °C, were investigated. 2 With increased temperature there was an increase in the mean distance of visited plants from the point of release and in the number of plants visited and infected with BYDV. Drought stress had no effect on mean distance moved by aphids at any temperature or on plants infected with virus at 10 °C and 5 °C. When plants were drought stressed, the numbers of plants visited and infected were greater at 15 °C than at 10 °C and 5 °C. 3 A greater proportion of plants visited by aphids was infected with BYDV when plants were stressed than when not stressed. At 15 °C a greater proportion of these plants was infected than at lower temperatures. There was no difference between treatments in the numbers of aphids present at the end of the experiment. 4 It is concluded that drought stress and temperature are of considerable importance in virus spread.     

Effect of heat stress on development in vitro and in vivo and on synthesis of heat shock proteins in porcine embryos

The present study was conducted (1) to examine the effect of an acute increase in ambient temperature on the development of porcine day 6 embryos in culture and after transfer to recipient gilts, and (2) to analyze intracellular production of heat shock proteins (hsps). The viability of porcine day 6 embryos following a temporary acute elevation in ambient temperature (at 42°–45.5°C and for 10–180 min) was examined. Synthesis of 70 kDa hsp (hsp 70) and 90 kDa hsp (hsp90) was determined by SDS-PAGE and Western blot analysis in porcine day 6 embryos subjected to heat stresses. Nonheat-stressed embryos were considered as control. Significantly higher numbers of viable nuclei were observed in treatment groups of 42°C-10 min (236.6 ± 71.4; P < 0.05) and 43°C-30 min (276.8 ± 89.4; P < 0.005) compared to control (173.9 ± 53.9). The 42°C-180 min group (158.0 ± 27.1 μm) had a greater increase in diameter after 24 hr in culture following heat stress compared to control (82.5 ± 47.3 μm), while heat stress with 43°C for ≧60 min, 44°–44.5°C for ≧30 min, or 45°-45.5°C for ≧10 min impaired their survival, as assessed by differences in number of viable nuclei. The embryos subjected to heat stresses under the conditions of 42°C-180 min, 43°C-10 min, 43°C-30 min, 44°C-10 min, or 45°C-10 min developed to normal piglets after transfer to recipient gilts. Overall pregnancy rate was 75% (6/8), and farrowing rate 62.5% (5/8). Of heat-stressed embryos transferred, 59% (36/61) developed to normal piglets. Heat-stress conditions of 42°C for 180 min, 43°C for 30 min, 44°C for 10 min, and 45°C for 10 min were determined as critical with respect to the in vitro and in vivo survival of porcine embryos. Porcine day 6 embryos constitutively synthesized hsp70 even without heat stress, while hsp90 was detected only at trace level. Neither hsp70 nor hsp90 levels increased in the embryos subjected to heat stresses. In conclusion, porcine day 6 embryos could continue to develop in vivo or during in vitro culture after exposure to acute and temporary rise in temperature. However, no increase of hsp70 and hsp90 was observed in the heat-stressed porcine embryos, while hsp70 was detected in the nonheat-stressed porcine embryos. The precise mechanism of the thermotolerance was unclear. © 1996 Wiley-Liss, Inc.     

Temperature measurements in a capacitive system of deep loco-regional hyperthermia

Hyperthermia has been shown to be a medically useful procedure applicable for different indications. For the connection between clinical effects and heat, it is important to understand the actual temperatures achieved in the tissue. There are limited temperature data available when using capacitive hyperthermia devices even though this is worldwide the most widespread method for loco-regional heating. Hence, this study examines temperature measurements using capacitive heating. Bioequivalent phantoms were used for the measurements, which, however, do not consider perfusion in live tissue. In general, the required temperature impact for an effective cancer therapy should need an increase of 0.2°C/min, which has been achieved. In the described tests on the non-perfused dummy, on average, the temperature increases by approximately 2°C in the first 12 min. The temperature difference relative to the starting temperature was 10–12°C within a therapy time of 60 min (rising from the initial room temperature between 20–24°C and 32–34°C). The average deviation with three individual measurements each on different days in a specified localization was 2°C. The minimum temperature difference was 4.2°C, and the maximum value was reached in the liver with 10.5°C. These values were achieved with a moderate energy input of 60–150 watts, with much higher performance outputs still available.

These results show that the tested capacitive device is capable of achieving quick temperature increase with a sufficient impact into the depth of a body.     

Effect of warming and grazing on litter mass loss and temperature sensitivity of litter and dung mass loss on the Tibetan plateau

Knowledge about the role of litter and dung decomposition in nutrient cycling and response to climate change and grazing in alpine ecosystems is still rudimentary. We conducted two separate studies to assess the relative role of warming and grazing on litter mass loss and on the temperature sensitivity of litter and dung mass loss. Experiments were conducted for 1–2 years under a controlled warming–grazing system and along an elevation gradient from 3200 to 3800 m. A free‐air temperature enhancement system (FATE) using infrared heaters and grazing significantly increased soil temperatures (average 0.5–1.6 °C) from 0 to 40 cm depth, but neither warming nor grazing affected soil moisture except early in the growing seasons at 30 cm soil depth. Heaters caused greater soil warming at night‐time compared with daytime, but grazing resulted in greater soil warming during daytime compared with night‐time. Annual average values of the soil temperature at 5 cm were 3.2, 2.4 and 0.3 °C at 3200, 3600 and 3800 m, respectively. Neither warming nor grazing caused changes of litter quality for the first year of the controlled warming–grazing experiment. The effects of warming and grazing on litter mass losses were additive, increasing litter mass losses by about 19.3% and 8.3%, respectively, for the 2‐year decomposition periods. The temperature sensitivity of litter mass losses was approximately 11% °C^?1 based on the controlled warming–grazing experiment. The annual cumulative litter mass loss was approximately 2.5 times that of dung along the elevation gradient. However, the temperature sensitivity (about 18% °C^?1) of the dung mass loss was about three times that of the litter mass loss. These results suggest greater warming at night‐time compared with daytime may accelerate litter mass loss, and grazing will enhance carbon loss to atmosphere in the region through a decrease of litter biomass and an increase of dung production with an increase of stocking rate in future warmer conditions.     

Temperature Effects on Shoot and Root Development From Begonia × cheimantha Petiole Segments Grown in vitro

The effect of different temperatures on the shoot and root formation in isolated petiole segments of Begonia × cheimantha was determined after 10 weeks on a modified White medium containing 0.1 mg/1 NAA and 0.5 mg/1 BA. Temperature proved to be important for the induction of shoot and root formation. At a constant temperature the best plants were obtained at 18 to21°C. If the temperature was higher, fewer cultures survived and the number of roots and shoots were lower. Lower temperatures inhibited the development of plants. A pretreatment at 15 or 18°C for two to four weeks improved the number and size of the shoots developed during a following 24°C treatment. High temperatures throughout the growing period reduced the number of shoots severely. A pretreatment of three days at 24°C or one day at 28°C reduced the shoot number by 50 %. After seven days at 28°C there was not a single shoot in any of the cultures. However, after two weeks at 15 or 18°C it was no longer possible to inhibit the shoot formation by a 24°C treatment. It is concluded that the formation of shoots in petiole segments takes place during the first two weeks after excision, and that high temperature is detrimental to the shoot initiation process.     

Temperature effects on the response to sulphur of barley,peas and rape

Summary The effects of temperature and sulphur nutrition on the growth, yield and mineral composition (N, NO₃-N, S and SO₄-S) ofHordeum vulgare L. cv Olli,Pisum sativum L. cv Dark Skin Perfection, andBrassica campestris L. cv Arlo, were investigated in controlled environments. When barley and rape plants were grown at O ppm S, deficiency symptoms developed in about two weeks, whereas peas at the same level developed deficiency symptoms in about three weeks. The location of the deficiency symptoms varied between species. Plant weight increased with increasing S levels, but the shoot had a greater growth response than did the root. Optimum day/night growing temperature regimes for barley and peas were found to be near 24/16 at four weeks from seeding and near 18/10°C at the mature stage as evident from weights, maximum fruit set and mineral uptake. Optimum temperature for rape plants was near 29/21°C at both stages of growth. Mineral concentration was higher at four weeks after seeding than at the mature stage in pea and rape plants, while in barley the mineral concentration was similar at both stages of growth. With increase in S supply there was an increase in concentration of both total S and SO₄-S. Concentrations also increased with increasing temperatures. S deficient plants had increased total N and NO₃-N concentrations in all three species. NO₃-N concentration also increased with an increase in temperature while total N concentration was not appreciably influenced. These experiments indicated that the effects of S nutrition on growth, development and mineral composition of plants depends on the species, temperature regime and growth stage     

Physiological responses of Opuntia ficus-indica to growth temperature

The influences of various day/night air temperatures on net CO₂ uptake and nocturnal acid accumulation were determined for Opuntia ficus-indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO₂ uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO₂ residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO₂ uptake at all growth temperatures. Nocturnal CO₂ uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO₂ uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non-optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO₂ uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange for O. ficus-indica and presumably for other CAM plants.     

Temperature effects on endogenous indole-3-acetic acid levels in leaves and stamens of the normal and male sterile 'stamenless-2' mutant of tomato (Lycopersicon esculentum Mill.)

The indole-3-acetic acid (IAA) concentration in leaves and stamens of the normal and a temperature-sensitive male sterile ‘stamenless-2′ (sl-2/sl-2) mutant of tomato (Lycopersicon esculentum Mill.), grown under three temperature conditions, was measured by gas chromatography — mass spectrometry — selected ion monitoring (GC-MS-SIM) and by enzyme-linked immunosorbant assay (ELISA). At low (LTR, 18°C day/15°C night), intermediate (ITR, 23°C day/18°C night), and high temperatures (HTR, 28°C day/23°C night), the mutant leaves had approximately 10 to 20 times higher IAA concentrations, respectively, than the normal leaves under these temperature regimes. Similarly, the stamens of mutant flowers had approximately five and eight times higher IAA concentration at ITR and HTR, respectively, than the normal flowers. In the low temperature reverted mutant stamens, however, the level of IAA was similar to that in normal stamens. Also, with an increase in temperature, there was an increase in the level of IAA in the leaves and stamens of mutant plants. However, different temperatures had no appreciable effect on the IAA content of leaves and stamens of normal plants. It is suggested that the high IAA content in leaves and stamens of the stamenless-2 mutant is one of the factors associated with male sterility and carpellization of stamens in this mutant.