Night Temperature Research Articles

Epidemiological Model based Decision Support System for the Management of Grapes Downy Mildew

Grapevine downy mildew caused by Plasmopara viticola is an explosivedisease that causes severe damage to leaf, flowers and fruits of the vine.In the present study, an epidemiological model was developed to supportthe vine-growers to reduce the number of fungicidal sprays and protect theenvironmental hazards besides saving the input cost. To record the weatherdata, an automatic weather station was installed at Mathampatti Village,Coimbatore, India and the weather parameters such as relative humidity,minimum, maximum and night temperatures, rainfall, leaf wetness, dew fall,solar radiation etc., were recorded at once in a 10 minutes interval during2014-17. A logistic equation was designed based on the biological data(disease incidence, weather parameter and crop age) and its mathematicalanalysis was shown in this paper. The critical weather parameters werestudied using logistic equation with the support of “Curve expert programme”.The mode described the development of the infection and infection ratethrough computation-based analysis. The Decision Support Systems (DSS)were arrived using the disease progress curve obtained from the logisticequation. The DSS indicates the first two sprays during the congenial phaseof the disease from 25 to 45 Days After Pruning (DAP). Then the secondphase, ie rapid growth stage was termed as ‘Exponential phase’, in which twosprays on 55 and 65 DAP (flowering and fruiting stage) were carried out. Inthe final plateau phase (66 DAP to till harvest), the management strategiesapplied would not be cost-effective and no spray was recommended. Thefield experiment was carried out using the findings of the logistic equationwith different management modules for validation. The number of spraysof fungicide was reduced from 15 to 5 times in the logistic equation-basedtreated plot.

Spatial heterogeneity of climate variation and vegetation response for Arctic and high-elevation regions from 2001–2018

In recent decades, an amplification of warming in Arctic and high-elevation regions has been widely observed, along with a general enhancement of vegetation growth. However, driven by variability in controlling factors and complex mechanisms, climate and vegetation changes can be highly heterogeneous in space and time. In this study, an analysis is performed separating Arctic and Tibetan Plateau (TP) vegetated areas into various units according to a map of terrestrial ecoregions. The most recent variations of heat, moisture, and vegetation growth (MODIS Normalized Difference Vegetation Index) are evaluated over 2001–2018. Relationships among the climate and vegetation variables are assessed. Six distinct change patterns are identified: (1) synchronized increase of day and night temperature and precipitation during April to October coinciding with strong vegetation greening, (2) profound warming with no change in precipitation and vegetation, (3) an increase of summer temperature and vegetation with a negative latitudinal gradient, (4) greening under increased precipitation without warming, (5) browning not likely being driven by climate, (6) warming only during the nighttime and moderately enhanced vegetation growth. It is demonstrated that vegetation growth in the Arctic and TP is largely controlled by nighttime temperature and precipitation, as opposed to daytime temperature. The exception is the Canadian Arctic, where greening is directly related to summer daytime warming, and a contrasting relationship is observed on the TP. The underlying causes of these patterns are discussed, relating them to multiple mechanisms reported in the literature. These findings may help to further understand the changing Arctic and high-elevation climate and its effects on vegetation growth.

Systematic determination of the reproductive growth stage most sensitive to high night temperature stress in rice (Oryza sativa)

AbstractHigh night‐temperature (HNT) stress during the reproductive stage of rice (Oryza sativa L.) reduces spikelet fertility and yield by inhibiting important physiological processes. However, specifics such as the period of time that is most sensitive to HNT, is unknown. To investigate this, we conducted four controlled‐environment experiments with two rice cultivars, N22 (HNT tolerant) and WAB56–104 (HNT susceptible). These cultivars were exposed to varying durations and intensities of night temperatures (control, 24°C; HNT, 30 and 35°C) during the reproductive stage. The effect of HNT on spikelet fertility and grain weight varied with duration: spikelet fertility reduced by 47–77% when exposed to HNT for 15 nights, 6–29% when exposed for four nights, and 9–15% when exposed for 5.5 h (pre‐midnight, 1830–0000 h or post‐midnight, 0000–0530 h) for four nights. Spikelet fertility and grain weight were most sensitive to HNT during the first 4 d of anthesis, compared with 1–4, 5–8, and 9–12 d before anthesis. At anthesis, reduction in spikelet fertility did not differ significantly between pre‐ and post‐midnight high‐temperature treatments. Our results suggest that greatest sensitivity to HNT during the reproductive stage occurs during the first 4 d of anthesis, providing a reference for future studies involving HNT tolerance in rice.

中国亚热带-暖温带过渡区锐齿栎林净生态系统碳交换特征

在2017年1月1日-2017年12月31日期间，采用涡度相关法对位于亚热带-暖温带气候过渡区的河南宝天曼国家级自然保护区的65年生锐齿栎（Quercus aliena）天然次生林的碳通量进行了连续观测。结果表明：在观测期间，该森林生态系统在生长季5-10月份为碳汇，非生长季各月为碳源，净碳吸收量与释放量分别在7月和4月达到最大。净生态系统生产力为569.4 g C m^-2a^-1，生态系统呼吸为529.9 g C m^-2a^-1，总生态系统生产力为1099.3 g C m^-2a^-1。30min尺度上夜间净生态系统碳交换量与5cm深度土壤温度的关系可用指数方程表示（R²=0.21，P < 0.001），其温度敏感性系数（Temperature sensitivity coefficient，Q₁₀）为2.2。如果排除夜间通量观测的误差，处在海拔较高地区的夜间低温和非生长季的低温抑制了生态系统呼吸排放，可能导致全年生态系统呼吸量较低。在生长季5-10月份，各月的白天净生态系统碳交换量对光合有效辐射的响应符合直角双曲线模型，初始光能利用效率、平均最大光合速率和白天平均生态系统呼吸强度呈明显的季节变化，范围分别是0.06-0.12 μmol CO₂ μmol^-1 photon、0.44-1.47 mg CO₂ m^-2s^-1和0.07-0.19 mg CO₂ m^-2s^-1。夏季7、8月份，较高的饱和水汽压差对白天锐齿栎林的碳吸收有明显的抑制作用；生长季末期9月份较高的土壤含水量对白天锐齿栎林的碳吸收也产生了抑制作用，表明生长末期降水过多影响森林的碳吸收。;Oak forests comprise the largest forest area in central China and are the potential carbon sink, while we know little about the carbon dioxide flux of oak forests in the transitional zone from subtropics to warm temperate, China. Using an open-path eddy covariance system and micro-climate instruments, the CO₂ flux, photosynthetic active radiation (PAR), air temperature, soil temperature and precipitation were simultaneously observed in a natural oak (Quercus aliena) forest at Baotianman National Nature Reserve. Based on the data sets during January to December 2017, dynamic change of CO₂ flux at different temporal scales and its underlying mechanism were analyzed. The results indicated that the diurnal and seasonal variations of CO₂ fluxes showed an obvious single peak pattern. The oak forest ecosystem was a carbon sink during the growing season (May-October), while a carbon source occurred during the non-growing season. Net carbon sequestration and emissions peaked in July and April, respectively. Mean annual net ecosystem productivity (NEP), ecosystem respiration (Re) and gross ecosystem productivity (GEP) were 569.4, 529.9 and 1099.3 g C m^-2 year^-1, respectively. The relationship between net ecosystem carbon exchange (NEE) measured at half-hour interval during night and soil temperature at depth of 5 cm can be expressed by an exponential equation (R²=0.21, P < 0.001), with its temperature sensitivity coefficient (Q₁₀) of 2.2. A low temperature at night and in the non-growing season at high elevation resulted in lower Re throughout the year. The relationship between NEE and PAR at daytime could be well expressed by a rectangular hyperbolic equation during growing seasons. Monthly initial light use efficiency, maximum photosynthetic capacity and daytime Re were 0.06-0.12 μmol CO₂ μmol^-1 photon, 0.44-1.47 mg CO₂ m^-2s^-1 and 0.07-0.19 mg CO₂ m^-2s^-1, respectively. Both higher vapour pressure deficit in July and August and higher soil moisture at the end of the growing season inhibited carbon uptake of the oak forest, indicating a negative effect of increased precipitation on carbon sequestration at the end of the growing season.

Influence of 4-CPA Growth Regulator for Enhancing Yield of Tomato During Low Night Temperature Stress

Influence of 4-CPA Growth Regulator for Enhancing Yield of Tomato During Low Night Temperature Stress

Selection of sowing date and biofertilization as alternatives to improve the yield and profitability of the F68 rice variety

Multiple factors influence rice yield. Developing management practices that increase crop yield and an efficient use of resources are challenging to modern agriculture. Consequently, the aim of this study was to evaluate biological nitrogen fixation and bacterial phosphorous solubilization (biofertilization) practices with the selection of the sowing date. Three sowing dates (May, July and August) were evaluated when interacting with two mineral nutrition treatments using a randomized complete block design in a split-plot arrangement. Leaf carbon balance, leaf area index, interception and radiation use efficiency, harvest index, dry matter accumulation, nutritional status, and yield were quantified. Results showed that the maximum yield was obtained in the sowing date of August. Additionally, yield increased by 18.92% with the biofertilization treatment, reaching 35.18% of profitability compared to the local production practice. High yields were related to a higher carbon balance during flowering, which was 11.56% and 54.04% higher in August than in July and May, respectively, due to a lower night temperature. In addition, a high efficient use of radiation, which in August was 17.56% and 41.23% higher than in July and May, respectively, contributed to obtain higher yields and this behavior is related to the selection of the sowing date. Likewise, a rapid development of the leaf area index and an optimum foliar nitrogen concentration (&gt;3%) were observed. This allowed for greater efficient use of radiation and is attributed to the activity of nitrogen-fixing and phosphate solubilizing bacteria that also act as plant growth promoters.

Seed germination response of a potential rangeland weed Psilocaulon granulicaule to selected environmental conditions

Studies show that just over 620 non-native naturalised plant species have been recorded within the Australian rangelands, some of which have a capacity to cause significant impacts on rangeland flora and grazing activity. Although Psilocaulon granulicaule (Haw.), Schwantes is listed as a highly invasive environmental weed species, there has been no previous research into its seed ecology. Therefore, this study was conducted to investigate the effects of temperature, light, pH, water stress, heat-shock, and salinity on the germination of P. granulicaule. In this study, four temperature regimes covering four different day and night temperature variations (17–7°C, 25–15°C, 30–25°C and 40–30°C) and two light regimes (12-h light–12-h dark, 24-h dark) were investigated. The effects of pH, water stress, heat-shock and salinity were investigated, using pH buffers, polyethylene glycol solutions, three heat shock events under four temperatures and a range of NaCl solutions. These tests were conducted under the identified optimum temperature range (25/15°C) and light regime for seed germination. The results showed that both temperature and photoperiod significantly influenced the germination rate, with 94.2% germination in the 25–15°C range under a 12-h light-12-h dark regime. Higher temperatures (30–40°C) reduced seed germination to &amp;lt;58% germination in both light regimes (57.5%, 12-h light-12-h dark; 54.17%, 24-h dark). The highest germination rates were observed in low pH solutions, high moisture levels, low heat-shocks and low salinity. The study showed that this species is sensitive to environmental factors such as temperature, light, pH, moisture, heat shock and salinity, suggesting that these factors can be used as critical indicators to guide effective management practices to address this weed problem. Given that seeds are sensitive to radiant heat, burning could be used as a tool to effectively manage this species.

A Review of Blast Disease of Rice in Nepal

Blast disease is caused by Magnaporthe grisea (syn. Pyricularia oryzae) firstly reported in 1637 from China. In Nepal it was firstly reported from Thimi, Bhaktapur in 1964. Symptoms of this disease appear in all stages from seedling in nursery to heading in main field, however, the most devastating stages are seedling stage, tillering stage and panicle initiation stage. Typical symptoms of blast appear on leaves, node, neck, collar, panicles, rachis and even the glumes are also affected. Globally, blast of rice is responsible for 10-30% of yield losses every year. In susceptible varieties the disease causes 10-20% yield reduction but in severe condition it went upto 80% in Nepal. Cloudy weather, high relative humidity (93-99%), low night temperature between 15-20°C, longer duration of dew are the most favorable condition for the outbreak of blast fungus. The most usual approaches for the management of rice blast disease are management in fertilizers and irrigations, plantation of resistant varieties and application of fungicides. Higher dose of nitrogen increase susceptibility so, it should be applied in split doses. Use of resistant cultivars such as Khumal-1, Khumal-2, Khumal-3, Radha-12, Chandannath-1, Chandannath-3, Sabitri and Palung-2 for the management of rice blast is sustainable and ecofriendly approach. Seed treatment with Trichoderma viridae at 4 g/kg or Pseudomonas fluorescens at 10 g/kg help to inhibit growth of blast fungus. Use of chemical named Kasugamycin used to control blast fungus is most commonly used and popular among Nepalese farmers.

“Covering Effects” under Diurnal Temperature Variations in Arid and Semiarid Areas

“Covering effects” dominated by water vapor migration in arid and semiarid areas threaten the stability of engineering entities. To explore the “covering effects” dominated by water vapor migration under the influence of diurnal temperature variations, a series of one‐side evaporation experiments were conducted. Characteristics of water vapor migration between the unsaturated loess soil column with and without a lid were compared in detail to illustrate the “covering effects” on water vapor migration, as were the effects of test time. Further, the characteristics of “covering effects” in loess and sand soil columns were compared. The results show that the “covering effects” formed in the loess soil column with a lid by cycling day and night temperature differences led water vapor to accumulate and condense beneath the lid. However, unlike the “covering effects” during freezing conditions that lead to a significant increase in the moisture content in the top layer, in this study, the moisture content in the top layer (0–8 cm) decreased. Although “soil lid” and the “soil covering effects” exist in both loess soil columns with and without lids, the “soil covering effects” for the former are much more obvious, and the moisture content in the upper part of the loess soil column (8–45 cm) shows a significant increase. By cycling day and night temperature differences, the “covering effects” or “soil covering effects” grew as the test time increased. Compared to the loess soil column, the “covering effects” in the sand soil column were extremely weak, and the moisture migration in the sand soil column was dominated by the downward movement liquid water. This paper illustrates the “covering effects” under the influence of diurnal temperature variations and reveals the mechanism of water vapor migration in subgrade soils in arid and semiarid areas.

THE EFFECTS OF TEMPERATURE AND MOISTURE STRESS CONTENT ON THE EXTENSIVE CULTIVATION OF THE OYSTER MUSHROOM

Oyster mushroom (Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm.) is involved in the destruction of dead wood which is the main place of settlement of several living organisms. After humification, dead wood also becomes an important component of forest soils. The purpose of the research is to study temperature and moisture conditions of extensive cultivation of oyster mushrooms on various wood substrates. To accomplish this goal, the following tasks were set: to determine the amount of effective stress temperatures and moisture content of substrates and their influence on the appearance of fruiting bodies of the oyster mushroom; to study the features of the extensive cultivation of oyster mushrooms on the tree stumps of cutover areas, in the hollows of broadleaved trees, using brushwood, on inoculated log sections in trenches, on log sections of dead dry trees. The oyster mushroom fruiting bodies collected in the suburban forest formed the basis of the experiment on the inoculation of different types of substrates. The inoculation of the log sections was carried with a relative air humidity of 85%, the process of overgrowing lasted from 2 to 3 months. The edaphic-climatic factors of different types of space - closed and open - were taken into account. The amount of effective temperatures necessary for the development of fruiting bodies has been determined. It was found that the intensive growth of the mushroom fruiting bodies begins after a sharp cooling (a drop in night temperatures to 4-8 ° C), which causes a stressful state of the mushroom. The amount of the effective stress temperatures is 4.6 ° C. Long-term phenological observations have revealed that the amount of the effective temperatures in the spring is 76.4 ° C, and in the autumn - 59.4 ° C. The duration of fruiting of oyster mushroom on log sections of hardwoods is 14 days in spring and 17 days in autumn longer than on softwoods blocks. It was found that the biomass of the fruiting bodies is directly dependent on the thickness of the log section, and, therefore, it is recommended to use log sections ranging from 35 cm to 50 cm in diameter and up to 30 cm in length.

Reduction in seed set upon exposure to high night temperature during flowering in maize.

High temperature reduces crop production; however, little is known about the effects of high night temperature (HNT) on the development of male and female reproductive organs, pollination, kernel formation and grain yield in maize (Zea mays L.). Therefore, a temperature-controlled experiment was carried out using heat-sensitive maize hybrid and including three temperature treatments of 32/22°C (day/night; control), 32/26°C and 32/30°C during 14 consecutive days encompassing the flowering stage. When exposed to 30°C night temperature, grain yield and kernel number reduced by 23.8 and 25.1%, respectively, compared with the control. The decrease in grain yield was mainly because of the lower kernel number rather than change in kernel weight under HNT exposure around flowering. No significant differences in grain yield and kernel number were found between 22 and 26°C night temperatures. HNT had no significant effects on the onset of flowering time and anthesis-silking interval but significantly reduced time period of pollen shedding duration and pollen viability, and increased leaf night respiration. Different from high daytime temperature, HNT had no lasting effects on daytime leaf photosynthesis, biomass production and assimilate transportation. From the perspective of source-flow-sink relationship, the unchanged source and flow capacities during daytime are supposed to alleviate the adverse effects on sink strength caused by HNT compared with daytime heat stress. These new findings commendably filled the knowledge gaps concerning heat stress in maize.

NOCTURNAL AND DIURNAL TRENDS OF SURFACE URBAN HEAT ISLAND INTENSITY: A SEASONAL VARIABILITY ANALYSIS FOR SMART URBAN PLANNING

Abstract. Land management in the limited environment of city regions with immense population pressure is a challenging task. To achieve the goal of sustainable smart cities, reliable spatial information needs to be incorporated in land governance policies. In this study, Landsat 8 satellite bands were processed to derive the land use characteristics which are causing the development of urban heat islands at certain locations. To assess the prolonged effects of heat-trapping in cities, night time temperature data was obtained through in-situ data collection with error within 1 °C. Much higher intensity of urban heat island was observed during the night. The maximum increase of 1.67 °C was noted from day to night temperature for the same heat island. Seasonal analysis between winter and summer months was also carried out. The results suggested that for both day and night summer months produced more critical heat islands with maximum intensity up to 3.48 °C; while in winter the heat island intensity did not exceed 2.18 °C. Through comparative analysis between two cities with varying extent, urbanization and population pressure, it was observed that the maximum intensity of day time temperature was greater in a bigger city and heat islands were less fragmented. Heat islands covered an area of 10.39 km2 over Prayagraj and 28.29 km2 area of Kolkata. The temperature patterns obtained during day and night were statistically validated with the index of impervious surface area, at the significance level of α0.05.

Traits Affecting Low Temperature Tolerance in Tomato and Its Application to Breeding Program

It is essential to develop tomato (Solanum lycopersicum L.) cultivars with tolerance to low temperature (LT) for reducing production cost and increasing fruit quality in winter. This study was conducted to investigate the effects of LT on 40 tomato accessions for establishing selection criteria to select accessions with LT tolerance. Tomato plants were grown in two polyethylene film greenhouses with night temperature set-points of 10℃ and 15℃. LT significantly affected the photosynthetic parameters as well as both vegetative and reproductive growth in tomato. There was a significant difference in plant height between plants grown in 10℃ and 15℃. Leaf length and width were also significantly lower in 10℃. The stem diameter was generally lower in 10℃ but 12 accessions in 10℃ had thicker stem diameter than those in 15℃. The retarded growth was due to lower photosynthetic rate in 10℃ than 15℃. Significant delay in flowering was observed among tomato accessions in 10℃. For the number of flowers, 62.5% showed the increase but 37.5% did the decrease in 10℃ among 40 tomato accessions, showing genotype specific interaction with LT. Accessions with small fruits showed reduced fruit set in 10℃; however, it was not obvious among accessions with large fruits. Interestingly, 75% of accessions showed increased chlorophyll contents in 10℃ compared to 15℃. An accession ‘VI037163’ was selected for LT tolerance based on good performance in six out of seven traits considered such as plant height, leaf length, stem diameter, chlorophyll contents, days to flowering, the number of flowers and fruit set.

Pattern and Trend of Night Land Surface Temperature in Africa

This study aims to identify patterns and trends of the night land surface temperature over eight day period from 2000 to 2014 in Africa using statistical analysis. Data were obtained from the United States National Aeronautics and Space Administration satellite, comprising 99 locations of 5° by 5° latitude and longitude grid-boxes between latitudes 35° north and south of the equator and longitudes 20° west to 50° east. First, the variation in the night surface temperatures was removed. Then, the trend of seasonally adjusted night temperatures was estimated using linear regression. The correlations between adjoining regions were considered by using factor analysis to classify the temperatures into four regions. Cubic spline models were fitted to the data within these regions to investigate patterns of the temperatures. The result showed that temperatures in most regions of Africa increased. The temperatures decreased was observed in southern Africa and parts of central and eastern Africa.

High night temperature induced changes in grain starch metabolism alters starch, protein, and lipid accumulation in winter wheat.

Unlike sporadic daytime heat spikes, a consistent increase in night-time temperatures can potentially derail the genetic gains being achieved. Ten winter wheat genotypes were exposed to six different night-time temperatures (15-27°C) during flowering and grain-filling stages in controlled environment chambers. We identified the night-time temperature of 23o C as the critical threshold beyond which a consistent decline in yields and quality was observed. Confocal laser scanning micrographs of central endosperm, bran, and germ tissue displayed differential accumulation of protein, lipid, and starch with increasing night-time temperatures. KS07077M-1 recorded a decrease in starch and an increase in protein and lipid in central endosperm with increasing night-time temperatures, whereas the same was significantly lower in the tolerant SY Monument. Expression analysis of genes encoding 21 enzymes (including isoforms) involved in grain-starch metabolism in developing grains revealed a high night-time temperature (HNT)-induced reduction in transcript levels of adenosine diphosphate glucose pyrophosphorylase small subunit involved in starch synthesis and a ≥2-fold increase in starch degrading enzymes isoamylase III, alpha-, and beta-amylase. The identified critical threshold, grain compositional changes, and the key enzymes in grain starch metabolism that lead to poor starch accumulation in grains establish the foundational knowledge for enhancing HNT tolerance in wheat.

Great tits responding to territorial intrusions sing less but alarm more on colder days

AbstractBird song transmits information required to defend territories and attract mates. These functions contribute to fitness by affecting survival and reproductive success. Singing is also costly due to physiological costs. We used observational data to evaluate support for the hypothesis that lower temperatures result in decreased singing behaviour in wild great tits due to increased energy consumption during cold conditions required for thermoregulation. More than 6,500 simulated territorial intrusions were performed over an 8‐year period in twelve nest box populations of great tits Parus major south of Munich, Germany. We measured song rate as well as the number of alarm calls and the aggressive response of territorial males to a simulated territorial intrusion. We found a decrease in song rate with decreasing current temperature, but also a concurrent increase in the number of alarm calls. Night temperature did not affect these acoustic traits. We conclude that warmer conditions allow birds to choose more energetically expensive (yet functionally superior) activities during territorial intrusions, thereby facilitating avoidance of physical aggressiveness during territorial intrusions.

Responses of Rice Growth to Day and Night Temperature and Relative Air Humidity-Dry Matter, Leaf Area, and Partitioning.

Asymmetric changes of day and night temperature have already been observed because of Climate Change. However, knowledge on environmental conditions either during day or night serving as trigger for growth processes is scarce. In this study, one rice (Oryza sativa) variety (IR64) was examined to assess the impact of varying temperatures and relative air humidities during day and night periods on biomass, leaf area, and dry matter partitioning between organs. Three different day and night temperature (30/20 °C, 25/25 °C, 20/30 °C) and relative air humidity (40/90%, 65/65%, 90/40%) regimes were established. The effect of relative air humidity on both plant dry matter and leaf area was larger than the effect of temperature, in particular low humidity had a strong negative impact during the night. With high day temperature, the shoot mass fraction increased, whereas the root mass fraction decreased. Specific leaf area increased at high night temperatures and led, along with the high leaf mass fraction at high night humidities, to higher growth rates. The results emphasize the importance of considering relative air humidity when focusing on plant responses to temperature, and strongly suggest that under asymmetric day and night temperature increases in the future, biomass partitioning rather than biomass itself will be affected.

Evaluation of chemical fruit thinning efficiency using Brevis® (Metamitron) on apple trees (‘Gala’) under Spanish conditions

Thinning is an important technique in apple growing which is used to reduce the number of fruits per plant and achieve commercial fruit size and quality. The objective of this work was to evaluate the efficacy of one and two applications of the chemical thinner Brevis® in Gala apple applied at different fruit sizes and at different intervals between the first and second spray. The trials were conducted over two seasons from 2015 to 2016 in apple orchards of the IRTA experimental agricultural stations of Mas Badia and Lleida (Spain). One or two applications with Brevis® were applied at different fruit sizes (king fruit diameter ranging between 7.5 and 13.5 mm) and at a rate of 1.65 kg/ha for all treatments. Under the trial conditions, a Brevis® thinning effect was observed in all trials with a reduction in crop load, fruit set and number of fruits per tree which varied according to the number of applications. In addition, average fruit weight, color and diameter increased significantly with treatments in which Brevis® reduced the number of fruits per tree. The degree of abscission of Brevis® was highly dependent on night temperature and, for this reason, there was a high degree of variability between trials in terms of efficacy. Our results show that the number of days between applications was not as important a factor for Brevis® efficacy as the difference in night temperature in the days immediately after its application.

The Atmospheric Circulation of Ultra-hot Jupiters

Abstract Recent observations of ultra-hot Jupiters with dayside temperatures in excess of 2500 K have found evidence for new physical processes at play in their atmospheres. In this work, we investigate the effects of the dissociation of molecular hydrogen and recombination of atomic hydrogen on the atmospheric circulation of ultra-hot Jupiters. To do so, we incorporate these effects into a general circulation model (GCM) for hot Jupiter atmospheres and run a large suite of models varying the incident stellar flux, rotation period, and strength of frictional drag. We find that including hydrogen dissociation and recombination reduces the fractional day-to-night temperature contrast of ultra-hot Jupiter atmospheres and causes the speed of the equatorial jet to decrease in simulations with fixed rotation. This is because the large energy input required for hydrogen dissociation cools the dayside of the planet, and the energy released due to hydrogen recombination warms the nightside. The resulting decrease in the day-to-night temperature contrast reduces the day-to-night pressure gradient that drives the circulation, resulting in weaker wind speeds. The results from our GCM experiments qualitatively agree with previous theory that found that the fractional day–night temperature contrast of ultra-hot Jupiters should decrease with increasing equilibrium temperature owing to hydrogen dissociation and recombination. Lastly, we compute full-phase light curves from our suite of GCM experiments, finding that the reduced day-to-night temperature contrast in ultra-hot Jupiter atmospheres causes a smaller phase curve amplitude. The reduction in phase curve amplitude due to hydrogen dissociation and recombination could explain the relatively small phase curve amplitudes of observed ultra-hot Jupiters.

Metabolic Dynamics of Developing Rice Seeds Under High Night-Time Temperature Stress.

High temperature stress during rice reproductive development results in yield losses. Reduced grain yield and grain quality has been associated with high temperature stress, and specifically with high night-time temperatures (HNT). Characterizing the impact of HNT on the phenotypic and metabolic status of developing rice seeds can provide insights into the mechanisms involved in yield and quality decline. Here, we examined the impact of warmer nights on the morphology and metabolome during early seed development in six diverse rice accessions. Seed size was sensitive to HNT in four of the six genotypes, while seed fertility and seed weight were unaffected. We observed genotypic differences for negative impact of HNT on grain quality. This was evident from the chalky grain appearance due to impaired packaging of starch granules. Metabolite profiles during early seed development (3 and 4 days after fertilization; DAF) were distinct from the early grain filling stages (7 and 10 DAF) under optimal conditions. We observed that accumulation of sugars (sucrose, fructose, and glucose) peaked at 7 DAF suggesting a major flux of carbon into glycolysis, tricarboxylic acid cycle, and starch biosynthesis during grain filling. Next, we determined hyper (HNT > control) and hypo (HNT < control) abundant metabolites and found 19 of the 57 metabolites to differ significantly between HNT and control treatments. The most prominent changes were exhibited by differential abundance of sugar and sugar alcohols under HNT, which could be linked to a protective mechanism against the HNT damage. Overall, our results indicate that combining metabolic profiles of developing grains with yield and quality parameters under high night temperature stress could provide insight for exploration of natural variation for HNT tolerance in the rice germplasm.