Increase In Night Temperature Research Articles

High night temperature induces contrasting responses for spikelet fertility, spikelet tissue temperature, flowering characteristics and grain quality in rice.

Climate change is increasing night temperature (NT) more than day temperature (DT) in rice-growing areas. Effects of combinations of NT (24-35°C) from microsporogenesis to anthesis at one or more DT (30 or 35°C) at anthesis on rice spikelet fertility, temperature within spikelets, flowering pattern, grain weight per panicle, amylose content and gel consistency were investigated in contrasting rice cultivars under controlled environments. Cultivars differed in spikelet fertility response to high NT, with higher fertility associated with cooler spikelets (P<0.01). Flowering dynamics were altered by high NT and a novel high temperature tolerance complementary mechanism, shorter flower open duration in cv. N22, was identified. High NT reduced spikelet fertility, grain weight per panicle, amylose content and gel consistency, whereas high DT reduced only gel consistency. Night temperature >27°C was estimated to reduce grain weight. Generally, high NT was more damaging to grain weight and selected grain quality traits than high DT, with little or no interaction between them. The critical tolerance and escape traits identified, i.e. spikelet cooling, relatively high spikelet fertility, earlier start and peak time of anthesis and shorter spikelet anthesis duration can aid plant breeding programs targeting resilience in warmer climates.

Arbuscular mycorrhizal symbiosis can mitigate the negative effects of night warming on physiological traits of Medicago truncatula L

Elevated night temperature, one of the main climate warming scenarios, can have profound effects on plant growth and metabolism. However, little attention has been paid to the potential role of mycorrhizal associations in plant responses to night warming, although it is well known that symbiotic fungi can protect host plants against various environmental stresses. In the present study, physiological traits of Medicago truncatula L. in association with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis were investigated under simulated night warming. A constant increase in night temperature of 1.53°C significantly reduced plant shoot and root biomass, flower and seed number, leaf sugar concentration, and shoot Zn and root P concentrations. However, the AM association essentially mitigated these negative effects of night warming by improving plant growth, especially through increased root biomass, root to shoot ratio, and shoot Zn and root P concentrations. A significant interaction was observed between R. irregularis inoculation and night warming in influencing both root sucrose concentration and expression of sucrose synthase (SusS) genes, suggesting that AM symbiosis and increased night temperature jointly regulated plant sugar metabolism. Night warming stimulated AM fungal colonization but did not influence arbuscule abundance, symbiosis-related plant or fungal gene expression, or growth of extraradical mycelium, indicating little effect of night warming on the development or functioning of AM symbiosis. These findings highlight the importance of mycorrhizal symbiosis in assisting plant resilience to climate warming.

High Night Temperatures During the Floral Bud Stage Increase the Abscission of Reproductive Structures in Cotton

AbstractCotton‐producing regions throughout the world often experience high night temperatures (HNTs), affecting flowering and yield in cotton (Gossypium hirsutum). The objective of this study was to quantify the effects of high nighttime temperatures on the physiological and biochemical characteristics of cotton during the floral bud and flowering stages. Growth chamber experiments were conducted in 2011–2012 and treatments included a control (day/night temperature of 32/24 °C) and two HNT treatments (32/29 °C from 8:00 pm to 12:00 am) for 3 weeks from the beginning of each phenological stage, i.e., first floral bud (B1) and first flower (F1). The results indicated that increased night temperatures (NTs) during the floral bud and flowering stages increased the rate of flower production per plant. However, no increase was observed in the final number of reproductive structures because the rate of floral abortion also increased for both treatments compared to the control. Additionally, the increase in night temperature during the floral bud stage reduced the sucrose content in the flower, resulting in decreased pollen viability and premature abortion of reproductive structures while the onset of flowering period was also delayed and lower accumulation of reproductive dry matter was observed. HNTs during the flowering stage reduced the number of seeds per locule and the number of seeds per boll. In general, higher than optimum NTs affected sucrose metabolism of the cotton flower and consequently its pollen viability. As a result the flowering period was delayed and a reduction in reproductive dry matter accumulation was observed due to premature abortion of reproductive structures. Finally, cotton is more sensitive to HNT at floral bud stage and this finding may be important to adjust cotton planting date, management and breeding.

Assessing future changes in seasonal climatic extremes in the Ganges river basin using an ensemble of regional climate models

Using an ensemble of four high resolution (~25 km) regional climate models, this study analyses the future (2021–2050) spatial distribution of seasonal temperature and precipitation extremes in the Ganges river basin based on the SRES A1B emissions scenario. The model validation results (1989–2008) show that the models simulate seasonality and spatial distribution of extreme temperature events better than precipitation. The models are able to capture fine topographical detail in the spatial distribution of indices based on their ability to resolve processes at a higher regional resolution. Future simulations of extreme temperature indices generally agree with expected warming in the Ganges basin, with considerable seasonal and spatial variation. Significantly warmer summers in the central part of the basin along with basin-wide increase in night temperature are expected during the summer and monsoon months. An increase in heavy precipitation indices during monsoon, coupled with extended periods without precipitation during the winter months; indicates an increase in the incidence of extreme events.

Effects of Increased Night Temperature on Cellulose Synthesis and the Activity of Sucrose Metabolism Enzymes in Cotton Fiber

Temperature is one of the key factors that influence cotton fiber synthesis at the late growth stage of cotton. In this paper, using two early-maturing cotton varieties as experimental materials, night temperature increase was stimulated in the field using far-infrared quartz tubes set in semi-mobile incubators and compared with the normal night temperatures (control) in order to investigate the effects of night temperature on the cotton fiber cellulose synthesis during secondary wall thickening. The results showed that the activity of sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) quickly increased and remained constant during the development of cotton fiber, while the activity of acid invertase (AI) and alkaline invertase (NI) decreased, increased night temperatures prompted the rapid transformation of sugar, and all the available sucrose fully converted into cellulose. With night temperature increasing treatment, an increase in SuSy activity and concentration of sucrose indicate more sucrose converted into UDPG (uridin diphosphate-glucose) during the early and late stages of cotton fiber development. Furthermore, SPS activity and the increased concentration of fructose accelerated fructose degradation and reduced the inhibition of fructose to SuSy; maintaining higher value of allocation proportion of invertase and sucrose during the early development stages of cotton fiber, which was propitious to supply a greater carbon source and energy for cellulose synthesis. Therefore, the minimum temperature in the nightime was a major factor correlated with the activity of sucrose metabolism enzymes in cotton fiber. Consequently, soluble sugar transformation and cellulose accumulation were closely associated with the minimum night temperature.

Study of dust haze in arid zone

Regularities in the effect of dust haze on the thermal regime of the air surface layer are revealed by examining air-temperature measurement data obtained at the Dushanbe, Termez, Bairam-Ali, Repetek, and Kurgan-Tyube meteorological stations. We find that the sharp decrease in daily air temperature and the slight increase in night temperature until the 1990s under strong dust storms leads to decreased temperatures in the air surface layer. Later, dust hazes of 3 to 8 days are more frequently observed with a pulsating change in the horizontal range of visibility. Depending on their power, these hazes lead to either heating or cooling of the atmospheric surface layer.

Elevation of night-time temperature increases terpenoid emissions from Betula pendula and Populus tremula.

Volatile organic compounds (VOCs) are expected to have an important role in plant adaptation to high temperatures. The impacts of increasing night-time temperature on daytime terpenoid emissions and related gene expression in silver birch (Betula pendula) and European aspen (Populus tremula) clones were studied. The plants were grown under five different night-time temperatures (6, 10, 14, 18, and 22 °C) while daytime temperature was kept at a constant 22 °C. VOC emissions were collected during the daytime and analysed by gas chromatography–mass spectrometry (GC-MS). In birch, emissions per leaf area of the C11 homoterpene 4,8-dimethy1-nona-1,3,7-triene (DMNT) and several sesquiterpenes were consistently increased with increasing night-time temperature. Total sesquiterpene (SQT) emissions showed an increase at higher temperatures. In aspen, emissions of DMNT and β-ocimene increased from 6 °C to 14 °C, while several other monoterpenes and the SQTs (Z,E)-α-farnesene and (E,E)-α-farnesene increased up to 18 °C. Total monoterpene and sesquiterpene emission peaked at 18 °C, whereas isoprene emissions decreased at 22 °C. Leaf area increased across the temperature range of 6–22 °C by 32% in birch and by 59% in aspen. Specific leaf area (SLA) was also increased in both species. The genetic regulation of VOC emissions seems to be very complex, as indicated by several inverse relationships between emission profiles and expression of several regulatory genes (DXR, DXS, and IPP). The study indicates that increasing night temperature may strongly affect the quantity and quality of daytime VOC emissions of northern deciduous trees.

Environmental control of flowering and runnering in three contrasting populations of Fragaria chiloensis

SummaryEnvironmental control of flowering and runnering in three contrasting Fragaria chiloensis populations with geographic origins in Alaska, Oregon, and Chile have been studied under controlled environment conditions. All populations were principal short-day (SD) plants at intermediate temperatures (15°C or 21°C), while at low temperature (9°C) the ‘Alaska’ and ‘Chile’ populations were essentially day neutral. However, the populations had contrasting temperature responses for flowering in SD at both constant and fluctuating day/night temperatures. At a day temperature of 18°C, flowering increased with increasing night temperature from 9°C to 21°C in the ‘Alaska’ population, while the opposite trend was observed in the ‘Chile’ population. The sparsely flowering ‘Oregon’ population flowered only in SD within a narrow range of temperatures (15° – 18°C). Photoperiod (10, 16, or 20 h) had no effect on flower development at 18°C. All populations were runnering freely, but with different temperature and photoperiod modifications. It is concluded that the SD × temperature interaction in the flowering behaviour of the June-bearing cultivated strawberry, F. × ananassa, is inherited to a large extent from F. chiloensis, whereas the species does not appear to have contributed to the long-day (LD) flowering control in everbearing cultivars.

Temperature responses, flowering and fruit yield of the June-bearing strawberry cultivars Florence, Frida and Korona

The effect of night temperature on short day (SD) floral induction has been studied in three June-bearing strawberry cultivars of different geographic origin and compared with yield performance in the cool Nordic environment. At the optimum day temperature of 18 °C, the SD flowering response of the cultivars ‘Florence’ and ‘Korona’ increased significantly with increasing night temperature from 9 to 18 °C, while an optimum was reached at 15 °C in the cultivar ‘Frida’ that is selected under cool-environment conditions in Norway. Also, while saturated flowering response was obtained with 3 weeks of SD treatment at all temperatures in ‘Frida’, several plants of ‘Florence’ and ‘Korona’ failed to initiate flowers at 9 °C night temperature even with 5 weeks of SD. The effect of extended SD period was particularly pronounced in ‘Florence’. The slow SD floral induction response of ‘Florence’ was associated with a 2 week delay of anthesis in subsequent long day (LD) conditions at 21 °C. Yield performance of the same cultivars during 2 years under field conditions at Nes Hedmark and in North Norway also demonstrated that the yield potential of ‘Florence’ was not realized under the climatic conditions prevailing at these locations. In both years the yields varied significantly among the cultivars, ‘Frida’ having the highest yields followed by ‘Korona’, with ‘Florence’ far below. It is concluded that, in the Nordic environment, autumn (September) night temperatures are obviously sub-optimal for yield performance of some June-bearing strawberry cultivars, and that this effect is mediated by autumn temperature effects on flower initiation responses.

Increased night temperature reduces the stimulatory effect of elevated carbon dioxide concentration on methane emission from rice paddy soil

AbstractTo determine how elevated night temperature interacts with carbon dioxide concentration ([CO2]) to affect methane (CH4) emission from rice paddy soil, we conducted a pot experiment using four controlled‐environment chambers and imposed a combination of two [CO2] levels (ambient: 380 ppm; elevated: 680 ppm) and two night temperatures (22 and 32 °C). The day temperature was maintained at 32 °C. Rice (cv. IR72) plants were grown outside until the early‐reproductive growth stage and then transferred to the chambers. After onset of the treatment, day and night CH4 fluxes were measured every week. The CH4 fluxes changed significantly with the growth stage, with the largest fluxes occurring around the heading stage in all treatments. The total CH4 emission during the treatment period was significantly increased by both elevated [CO2] (P=0.03) and elevated night temperature (P&lt;0.01). Elevated [CO2] increased CH4 emission by 3.5% and 32.2% under high and low night temperature conditions, respectively. Elevated [CO2] increased the net dry weight of rice plants by 12.7% and 38.4% under high and low night temperature conditions, respectively. These results imply that increasing night temperature reduces the stimulatory effect of elevated [CO2] on both CH4 emission and rice growth. The CH4 emission during the day was larger than at night even under the high‐night‐temperature treatment (i.e. a constant temperature all day). This difference became larger after the heading stage. We observed significant correlations between the night respiration and daily CH4 flux (P&lt;0.01). These results suggest that net plant photosynthesis contributes greatly to CH4 emission and that increasing night temperature reduces the stimulatory effect of elevated [CO2] on CH4 emission from rice paddy soil.

Effects of High Night Temperature on Crassulacean Acid Metabolism (CAM) Photosynthesis of Kalanchoë pinnata and Ananas comosus

The effects of the night temperature on CO2 exchange rate and organic acid accumulation in the leaves of two crassulacean acid metabolism (CAM) plants, Kalanchoë pinnata and Ananas comosus (pineapple), were examined under a fixed day-temperature condition of 30°C. With the increase of the night temperature, the CO2 exchange rate decreased in both species, and K. pinnata completely lost nocturnal CO2 uptake under a high night temperature (30/37°C in day/night) condition (HNT). Malate accumulation in the leaves of pineapple and K. pinnata in the morning decreased with increasing night temperature, but that in the afternoon was not influenced by the night temperature. Diurnal changes of ten kinds of metabolites were investigated under HNT. Pineapple accumulated a large amount of nocturnal malate under HNT, but K. pinnata did not. Four kinds of hexose-phosphate (hexose-P) were accumulated at the same levels during the day/night cycle under HNT in both plant species. Nocturnal accumulation of oxaloacetate (OAA) was observed but phosphoenolpyruvate (PEP) was kept at a high level both in day and night under HNT in both plant species. The concentrations of malate required for 50% inhibition of the activities of day and night forms of PEP carboxylase (PEPC) from the pineapple leaves were 1.2 and 0.7 mM, respectively, whereas those from the K. pinata leaves were 3.7 and 2.0 mM, respectively. In both plants, NAD-MDH activity in vitro increased with increasing temperature. It is therefore suggested that under HNT, phosphorylation may not be the major factor controlling PEPC activity in pineapple, and therefore CAM mode in pineapple was maintained under HNT. The nighttime phosphorylation of PEPC in K. pinnata would disappear under HNT leading to the loss of nocturnal malate accumulation.

Night temperature affects fatty acid composition in sunflower oil depending on the hybrid and the phenological stage

Fatty acid composition is affected by plant genotype and environmental conditions with temperature a major effect. The effect of night temperature during different periods of fruit filling on the fatty acid composition of sunflower oil from hybrids with different potential oleic acid content has never been studied. This information is needed if we are further to improve oil quality. A traditional, a mid oleic and two high oleic hybrids were sown in the field on 3 November 1998. The traditional hybrid was also sown again on 22 November 1998. In each experiment, four treatments were applied; a control and three treatments in which night temperature was increased 6.9 °C at three different consecutive periods of 200 °C day after flowering. A third experiment was carried out in growth chambers using the same genotypes as in the previous experiments plus another high oleic hybrid. Three day–night temperatures (16–26, 22–20 and 26–16 °C) were applied to plants from flowering to physiological maturity. In general, oleic acid percentage was higher with higher night temperature and was not related to daily minimum temperature. The largest variation in oleic acid percentage was observed in the traditional hybrid and the lowest in the high oleic hybrids. Higher oleic acid percentage was associated with an increase in night temperature early during fruit filling. Variation in oleic acid percentage was related to variation in linoleic acid percentage in all experiments.

Influences of High Night Temperature on Flowering and Pod Setting in Soybean

Soybean (Glycine max (L.) Merr. cv. Enrei) plants were grown in pots (15-L volume) placed in a greenhouse with ventilation. At the time when the first flower opened, pots were transferred to growth chambers with natural lighting under day temperature of 30°C and night temperatures of 20, 25 or 30°C. The numbers of flowers opened and pods set each day were recorded and the seed yield and yield components were investigated after harvest. The increase in night temperature decreased the seed size and increased the number of flowers and pods. As a result, the seed weight per plant was unaffected by night temperature. However, high night temperatures increased the number of flowers on the secondary and tertiary racemes. These flowers opened after the 18th day of the flowering period and showed a high rate of pod setting. These results suggest that a high night temperature stimulated flower opening and pod setting in the secondary and tertiary racemes. The increases in the numbers of flowers and pods could serve to moderate the reduction of seed yield caused by a high night temperature.

Effect of plant growth temperature on antioxidant capacity in strawberry.

The influence of four day/night growing temperature combinations (18/12, 25/12, 25/22, and 30/22 degrees C) on phenolic acid, flavonol, and anthocyanin content and their antioxidant activities against peroxyl radicals (ROO(*)), superoxide radicals (O(2)(*)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radicals (OH(*)), and singlet oxygen ((1)O(2)) in fruit juice of Earliglow and Kent strawberry (Fragaria x ananassa Duch.) cultivars was studied. Pelargonidin-based anthocyanins such as pelargonidin 3-glucoside (291.3-945.1 microg/g fresh wt.), pelargonidin 3-rutinoside (24.7-50.9 microg/g fresh wt.), and pelargonidin 3-glucoside-succinate (62.2-244.0 microg/g fresh wt.) were the predominant anthocyanins in strawberry fruit juice. The content of cyanidin-based anthocyanins, cyanidin 3-glucoside and cyanidin 3-glucoside-succinate, was much lower than that of pelargonidin-based anthocyanins. Strawberry growth in high temperature conditions significantly enhanced the content of p-coumaroylglucose, dihydroflavonol, quercetin 3-glucoside, quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside, pelargonidin 3-glucoside, pelargonidin 3-rutinoside, cyanidin 3-glucoside-succinate, and pelargonidin 3-glucoside-succinate in strawberry juice. Plants grown in the cool day and cool night temperature (18/12 degrees C) generally had the lowest phenolic acid, flavonols, and anthocyanins. An increase in night temperature from 12 to 22 degrees C, with the day temperature kept constant at 25 degrees C, resulted in a significant increase in phenolic acid, flavonols, and anthocyanins. These conditions also resulted in a significant increase in antioxidant capacity. The highest day/night temperature (30/22 degrees C) yielded fruit with the most phenolic content as well as ROO(*), O(2)(*)(-), H(2)O(2), OH(*), and (1)O(2) radical absorbance capacity. Fruit of Kent cv. strawberry had higher values of phenolic acid, flavonols, anthocyanins, and antioxidant capacities than fruit of Earliglow cv. strawberry under all temperature regimes.

Night Temperature at Silking Affects Set in Maize

Maize (Zea mays L.) grain yield is primarily associated with variation in the number of mature kernels which, in turn, depends on crop growth at silking. This study was conducted to determine whether night temperature at silking could affect kernel set in maize. Two night thermal conditions: (i) ambient and (ii) ambient plus 5 degrees C, imposed from 1 wk before to 3 wk after silking in a well-watered and fertilized maize crop, were investigated in a field experiment at Balcarce, Argentina during the 1994-1995 growing season. Development rate was hastened by heating; tassels and silks appeared 1 d earlier and the lag phase of grain filling was shortened by 5 d. Control plots required seven more days to achieve the same thermal sum than heated plots during the heating period. Plant growth per day at silking did not differ between treatments since both the crop radiation interception and radiation use efficiencies remained unchanged. Differences in respiration losses were insignificant. Spikelet morphogenesis was not affected by heating. Nevertheless, kernel abortion was increased in heated plots (36 vs. 28% for controls, P < 0.02). Final kernel number was associated with plant growth rate at silking when rate was expressed per unit of thermal time. Thus, increased night temperature at silking affected kernel set in maize mainly through increasing development rate that reduced photoassimilate production per unit of thermal time, limiting photoassimilate availability to support kernel growth at the ear tip.

DEVELOPING RELATIONSHIPS BETWEEN ENVIRONMENTAL VARIABLES AND STEM ELONGATION IN CHRYSANTHEMUM

The main objective of this research was to model the relationships between the environmental variables and stem elongation in chrysanthemum with the end-goal of producing a model appropriate for use in the dynamic control of a greenhouse environment. The plants used were Dendranthema grandiflora cv. ‘Spice’. The model developed uses Richards’ growth equation (Richards, 1969) as its base. Adaptations were made to Richards’ growth equation to explicitly include the effects of day and night temperature, daily PPF (photosynthetic photon flux), end-of-day red to far-red ratio, and position of the internode on the stem on internode elongation. The model fit the observed final length data reasonably well (R2 = 0.89). Sensitivity analyses indicated that increasing day temperature had a positive effect on internode length while increasing night temperature had a negative effect, with night temperature having a considerably larger effect than the effect of day temperature. The analyses suggests that both high and low end-of-day red to far-red ratios will produce increased lengths and that increasing daily PPF will produce decreased lengths. The analyses also suggests that internodes which develop later on the plant will generally have larger lengths as reflected by the measured data.

Photoperiod and Temperature Interact to Affect Gomphrena globosa L. and Salvia farinacea Benth. Development

Gomphrena globosa L. `Gnome Pink' and Salvia farinacea Benth. `Victoria Blue' were grown under different photoperiod treatments with day and night temperatures ranging from 15 to 30°C ± 1°C air temperature for 14 weeks after germination or until anthesis. Days to anthesis and leaf number were lowest when plants were grown under 9 hr of daylight and daylight plus 4-hr day extension from 1700–2100 HR (100 μmol·m–2·s–1 from high-pressure sodium lamps) for Gomphrena and Salvia, respectively. Days to anthesis decreased as temperature increased from 15 to 25°C with Gomphrena. Further increasing night temperature from 25 to 30°C delayed flowering and increased leaf number below the first flower of Gomphrena, but hastened flowering of Salvia. Plant height and internode elongation were greatest and least in the night interruption (2 μmol·m–2·s–1 from incandescent lamps from 2200–0200 HR) and continuous light (daylight plus 100 μmol·m–2·s–1 from high-pressure sodium lamps) treatments, respectively. Implications of these data with respect to classification of Gomphrena and Salvia flower induction are discussed and revised production schedules are presented.

Soybean Seed Quality Reductions by High Day and Night Temperature

Environmental stress during reproductive growth of soybean [Glycine max (L.) Merr.] may reduce seed germination and vigor. Most studies of environmental influence on soybean seed germination and vigor have concentrated on the effects of drought, maximum day temperature, or average daily temperatured uring seed fill. This study was conducted to determine the effects of different combinations of day temperatures and night temperatures during reproductive growth on soybean seed quality. Day/night temperatures of 30/20, 30/30, 35/20, and 35/30°C were imposed at flowering and pod set (R1‐R5), seed fill and maturation (R5‐R8), and during the entire reproductive growth period (R1‐R8). High day and night temperature reduced soybean seed germination and seedling vigor. The extent of reductions in germination and vigor by high temperature was influenced by duration of temperature exposure and phase of reproductive growth. Temperatures during flowering and pod set exerted little influence on soybean seed quality. A combination of 35°C day temperature and 30°C night temperature during seed fill and maturation or 35°C day temperature from flowering to maturity decreased germination. Seedling vigor was reduced by 35/20, 30/30, and 35/30°C during seed fill and maturation and the entire reproductive period. Increase in night temperature from 20 to 30°C decreased seedling vigor at both 30 and 35°C day temperatures. These results suggest that Incational and seasonal differences in soybean seed quality may be induced by high temperatures during reproductive growth and indicate that night temperatures along with day temperatures are important in determining soybean seed quality.

Respiration and Growth of Sorghum and Sunflower under Predicted Increased Night Temperatures1

AbstractLittle information exists concerning how crops will respond to the predicted increased night temperatures. The objective of this work was to determine if respiration and growth of sorghum [Sorghum bicolor (L.) Moench], a C, plant, and sunflower (Helianthus annuus L.), a C3 plant, are affected when the night temperature is increased by 5°C compared to the long‐term (19 year) average night temperature in June in Kansas. Sorghum and sunflower were grown in two walk‐in growth chambers with either the ambient night temperature (21C) or a high night temperature (26C). Day temperature was the same for all plants (27C). Both sunflower and sorghum had higher respiration rates under the elevated night temperature than under the ambient temperature. The average respiration rate of sunflower grown under elevated night temperature increased by 19% (0.89 vs. 0.75 μmol m−2 s−1) and that of sorghum by 44 % (0.52 vs. 0.36μmol m−2s−1). After 74 days, sunflower plants grown under the ambient night temperature were 30.2 cm taller than sunflower plants grown under the elevated night temperature; sorghum plants under the ambient temperature were 24.8 cm taller. Sunflower plants grown under the elevated night temperature formed flowers one week earlier than those grown under the ambient temperature. Sorghum formed no flowers by 74 days. Results suggest that, if climate change does increase night temperature, respiration will be increased more in C4, than C3 plants.

Increasing Night Temperature Can Reduce Seed Set and Potential Yield of Tropical Rice

The effect of increasing day temperature on reducing seed set in rice is well established, but little is known concerning the impact of increasing night temperature relative to constant day temperature. Recent work suggests that anticipated global warming may be uneven, with a significant increase in night compared to day temperature. Sun-lit, outdoor environment chambers were used to determine the impact of increasing night temperatures at two constant day temperatures (29/21, 29/25, 29/29�C and 33/25, 33/29 and 33/33�C) as well as increasing day/night temperature (29/21, 33/25 and 36/29�C) on growth and yield of rice (cv. IR 72). Increasing daylnight temperature to 36/29�C resulted in a significant reduction in both plant biomass and grain yield at harvest. At a constant day temperature of 29�C, increasing night temperature did not significantly alter growth or yield; however, increasing night temperature at a day temperature of 33�C (8 h duration) resulted in a significant decline in grain yield, primarily due to reduced seed set. The decline in grain yield at 33�C with increasing night time temperature was similar to that observed at a daylnight temperature of 36/29�C. Data from this experiment suggest that higher night time temperatures per se could increase the susceptibility of rice to sterility with a subsequent reduction in seed set and grain yield.