Negative Effects Of Low Temperature Research Articles

PGPR alleviated the negative effects of low temperature and low light stress on the growth and physiology of violet plants

Plants in greenhouses are often exposed to low temperature and low light conditions in the winter, and this has a major effect on flower cultivation. Inoculation of plant growth-promoting rhizobacteria (PGPR) can improve the growth of plants under stress. Here, we examined the effects of Pseudomonas fluorescens on the growth, photosynthesis, chlorophyll fluorescence parameters, and antioxidant enzyme systems of violet plants (Matthiola incana) exposed to normal temperature and normal light intensity (18 °C/11 °C, 500 μmol·m-2·s-1, NN), low temperature and normal light intensity (4 °C/1 °C, 500 μmol·m-2·s-1, LN), normal temperature and low light intensity (18 °C/11°C, 100 μmol·m-2·s-1, NL), and low temperature and low light intensity (4 °C/1 °C, 100 μmol·m-2·s-1, LL). The results showed that the plant height, stem diameter, leaf area, shoot fresh/dry weight, and underground fresh/dry weight of violet inoculated with PGPR were 40%, 17%, 13%, 25%, 41%, 30%, and 38% higher than the control, respectively. In addition, the total root length, mean root diameter, number of root tips, number of bifurcated root tips, and root vigor were 24%, 23%, 14%, 30%, and 21% higher in the inoculated group than in the control group, respectively. PGPR promoted chlorophyll accumulation in plants, and the net photosynthetic rate of violets was 32% higher in plants inoculated with PGPR than in control plants. PGPR also significantly promoted the maximum photochemical conversion efficiency of photosystem II (PSII) and the potential activity of PSII under UV light. After inoculation with PGPR, the content of MDA decreased by 16.8%, and the activities of superoxide dismutase and peroxidase increased by 19.2% and 20.0%, respectively. Therefore, PGPR can promote the growth of violet plants by increasing the photosynthetic capacity, activating the antioxidant enzyme system, and reducing damage induced by exposure to low light intensity.

Machine learning-assisted optimization of food-grade spirulina cultivation in seawater-based media: From laboratory to large-scale production

The shortage of food and freshwater sources threatens human health and environmental sustainability. Spirulina grown in seawater-based media as a healthy food is promising and environmentally friendly. This study used three machine learning techniques to identify important cultivation parameters and their hidden interrelationships and optimize the biomass yield of Spirulina grown in seawater-based media. Through optimization of hyperparameters and features, eXtreme Gradient Boosting, along with the recursive feature elimination (RFE) model demonstrated optimal performance and identified 28 important features. Among them, illumination intensity and initial pH value were critical determinants of biomass, which impacted other features. Specifically, high initial pH values (>9.0) mainly increased biomass but also increased nutrient sedimentation and ammonia (NH3) losses. Both batch and continuous additions could decrease nutrient losses by increasing their availability in the seawater-based media. When illumination intensity exceeded 200 μmol photons/m2/s, it amplified the growth of Spirulina by mitigating the light attenuation caused by a high initial inoculum level and counteracted the negative effect of low temperature (<25 °C). In large-scale cultivation, production efficiency would be reduced if illumination was not maintained at a high level. High salinity and sodium bicarbonate (NaHCO3) addition promoted carbohydrate accumulation, but suitable dilution could keep the required protein content in Spirulina with relatively low media and production costs. These findings reveal the interactive influence of cultivation parameters on biomass yield and help us determine the optimal cultivation conditions for large-scale cultivation of Spirulina-based seawater system based on a developed graphical user interface website.

Different climate conditions drive variations in gross primary productivity and woody biomass accumulation in a temperate and a boreal conifer forest in Canada

Understanding the complex relationships between climate, forest carbon (C) uptake and biomass growth has become a research priority, crucial for assessing the climate change impacts on forest C sequestration. Such associations are expected to vary across biomes, due to different climate constraints on tree physiology. However, our understanding of the seasonal dynamics of long-term C sequestration and how climate influences them in different forest biomes is still limited.We investigated a boreal Pinus banksiana forest (Old Jack Pine, OJP) and a temperate Pinus strobus plantation (Turkey Point, TP39) in Canada. We aimed to assess the link between C uptake and above-ground woody biomass growth, and the effects of climate inter-annual variability on them. We used daily records of climate and gross primary productivity (GPP, period 1999–2019 at OJP and 2003–2018 at TP39), and investigated xylem biomass proxies at cell (cell wall area) and tree-ring level (ring wall area) from 1970 to 2019 at OJP, and from 1970 to 2018 at TP39.In both forests, the direct link between C sink and C source was revealed by the common inter-annual variability of GPP and xylem biomass. GPP and xylem biomass were mostly influenced by spring and late summer temperature at OJP. However, at both sites, summer drought negatively influenced GPP, and biomass growth especially in recent decades. Analysis of dry and cold years evidenced short-term negative effects of low temperature on GPP and xylem biomass in OJP, and of drought in TP39.Long-term intra-annual analyses are crucial to assess the variable effects of climate on forest C cycle. Warm spring and autumn can benefit both GPP and biomass growth, but even in the boreal forest, summer drought has negative impacts. Increasing dry spells, especially in the temperate site, could reduce future forest capacity to uptake C and fix it in wood biomass.

The quality and fertilizing ability of sperm after the addition of nanosuccinates of Mn, Cu, Zn to the medium for cryopreservation of ram sperm

In the process of cryopreservation of sperm, there are violations of the ultrastructure of spermatozoa, which causes biochemical and functional changes in them. To protect spermatozoa from the negative effects of low temperatures, cryopreservation media are used, to which trace elements are added. Recently, nanoforms of trace elements have been obtained in Ukraine and experiments have been started to study their effect on the animal body. The aim of the work was to find out the effect of adding nanosuccinate of Mn, Zn and Cu to the medium for cryopreservation of ram sperm on the quality and fertilizing ability of sperm. The experiment was conducted on six clinically healthy breeder rams, aged 2–4 years. After evaluating the ejaculate from six rams aged 2–4 years, the Texel breed was divided into control and experimental groups. Control sperm samples were diluted with lactose-yolk-tris-citrate-glycerin medium (LYTCGM). Nanosuccinates of microelements were added to the medium in test samples of ram sperm in the following doses: Zn and Mn – 2.5, 5.0 and 7.5 μg/l, Cu – 1.25, 2.5 and 3.75 μg/l. Diluted sperm was packaged in straws, equilibrated for 2.5 hours and frozen. After thawing of sperm, motility, percentage of damaged spermatozoa, their survival, activity of succinate dehydrogenase (SDH) and cytochrome oxidase (CO) in sperm were determined. A dose-dependent effect of Mn, Zn, and Cu nanocitrates upon their addition to LYTCGM was established. The addition of Mn and Zn nanosuccinate at a dose of 5.0 μg/l to LYTCGM probably increases the motility of ram spermatozoa after thawing, and also reduces the percentage of spermatozoa with morphological disorders. Addition of Cu nanosuccinate in increasing doses significantly reduces spermatozoa motility in thawed ram semen, simultaneously increasing the percentage of degenerate spermatozoa. After the addition of Mn and Zn nanosuccinate at a dose of 5.0 μg/l LYTCGM, the survival rate of ram spermatozoa is probably increased, and the addition of Cu nanosuccinate in increasing doses significantly reduces the survival time of germ cells. Addition of Mn and Zn nanosuccinate at a dose of 5.0 μg/l to LYTCGM probably increases the activity of SDH and CO in sperm after thawing, and the addition of Cu nanosuccinate in increasing doses significantly reduces the activity of these enzymes. The addition of Mn and Zn nanosuccinate in lower (2.5 μg/l) and higher (7.5 μg/l) doses did not significantly affect the motility, morphological disorders and survival of spermatozoa, as well as the activity of SDH and CO in them.

Sodium current preserves electrical excitability in the heart of hibernating ground squirrel (Citellus undulatus)

Hibernating mammals are capable of maintaining normal cardiac function at low temperatures. Excitability of cardiac myocytes crucially depends on the fast sodium current (INa), which is decreased in hypothermia due to both depolarization of resting membrane potential and direct negative effect of low temperature. Therefore, INa in hibernating mammals should have specific features allowing to maintain excitability of myocardium at low temperatures. The current-voltage dependence of INa, its steady-state inactivation and activation and recovery from inactivation were studied in winter hibernating (WH) and summer active (SA) ground squirrels and in rats using whole-cell patch clamp at 10 °C and 20 °C. INa peak amplitude and the parameters of steady-state activation and inactivation curves did not differ between SA and WH ground squirrels at both temperatures. However, at both temperatures strong positive shift of activation and inactivation curves by 5–12 mV was observed in both WH and SA ground squirrels if compared to rats. This peculiarity of cardiac INa in ground squirrels helps to maintain excitability in conditions of depolarized resting membrane potential. The time course of INa recovery from inactivation at 10 °C was faster in WH than in SA ground squirrels, which could ensure normal activation of myocardium during hibernation.

Genome‐wide association analysis of chilling‐tolerant germination in a new maize association mapping panel

AbstractMaize is a crop that is highly susceptible to the negative effects of low temperature. Low temperature can delay seed germination and cause a decrease in seed vigor, which seriously affects seedling emergence and yield. In this study, 190 maize accessions (inbred lines) with strong germination potential at normal temperature (25°C) were selected from more than 500 accessions to construct a new association mapping panel to further investigate germination under chilling stress (5°C). We re‐sequenced the genomes of the 190 diverse accessions and obtained 4,886,919 high‐quality SNPs. We then used this data to analyze population structure, perform principal components analysis, and construct a phylogenetic tree of the new maize panel. The relative germination rate (RGR) and relative germination index (RGI) are two traits that are significantly related to chilling‐tolerant germination. Genome‐wide association analysis showed that RGR and RGI shared a major QTL, and they also shared the top SNP. There were a total of 26 significant SNPs in common. These SNPs hit directly or indirectly within 37 candidate genes. Among these 37 gene candidates, eight are homologs of genes previously reported to be related to both germination and low‐temperature stress, and another 12 genes related to low‐temperature stress or other abiotic stresses such as drought, salinity, oxidative, and high light stress. In addition, RGR and RGI had another 15 and 26 significant SNPs, respectively, which were associated with 17 and 92 candidate genes, respectively. Further qRT‐PCR analysis using 26 chilling‐tolerant and 22 chilling‐sensitive accessions implied that Zm00001eb272370, Zm00001eb272390, and Zm00001eb272400 associated with the top SNP, may play different roles during cold‐germination. Thus, our study not only established a new association mapping panel suitable for investigation of germination at low temperature but also provided valuable genetic resources for future studies to improve chilling‐tolerant maize varieties.

Integrated metabolism and epigenetic modifications in the macrophages of mice in responses to cold stress.

The negative effects of low temperature can readily induce a variety of diseases. We sought to understand the reasons why cold stress induces disease by studying the mechanisms of fine-tuning in macrophages following cold exposure. We found that cold stress triggers increased macrophage activation accompanied by metabolic reprogramming of aerobic glycolysis. The discovery, by genome-wide RNA sequencing, of defective mitochondria in mice macrophages following cold exposure indicated that mitochondrial defects may contribute to this process. In addition, changes in metabolism drive the differentiation of macrophages by affecting histone modifications. Finally, we showed that histone acetylation and lactylation are modulators of macrophage differentiation following cold exposure. Collectively, metabolism-related epigenetic modifications are essential for the differentiation of macrophages in cold-stressed mice, and the regulation of metabolism may be crucial for alleviating the harm induced by cold stress.

Sludge dewaterability enhancement under low temperature condition with cold-tolerant Bdellovibrio sp. CLL13

The dewatering performance of waste activated sludge (WAS) is generally deteriorated under low temperature due to the increase of viscosity, which would exacerbate the difficulties in sludge treatment and disposal. In this study, the cold-tolerant Bdellovibrio sp. CLL13 was successfully screened for efficient sludge biolysis, and it dramatically improved the sludge dewaterability while no significant biolysis effects were observed for the mesophilic BALO strain at 12 °C. The reduction rates of the sludge capillary suction time (CST), the specific resistance of filtration (SRF), the sludge dry weight, and the fecal coliform bacteria concentration at the optimal reaction time of 14 h were 40.1 ± 0.2%, 69.6 ± 0.7%, 7.7 ± 0.4%, and 78.5 ± 0.4%, respectively, when the mixed liquid suspended solids (MLSS) content was between 10.8 and 29.6 g/L, the input dosage of CLL13 was 8.8 × 106 PFU/mL sludge, and the DO level was 1.2 mg/L. Meanwhile, the viscosity reduction rate, the relative hydrophobicity increasement rate, and the bound water reduction rate were 20.3 ± 1.2%, 6.9 ± 0.7%, and 29.4 ± 1.0%, respectively. The ratios of protein content to polysaccharides content in the extracellular polymeric substances (EPS) decreased significantly. In addition, the degradation of the macromolecular substances in EPS and the increase of the soluble chemical oxygen demand, the total nitrogen, the total phosphorus, and the lactate dehydrogenase levels were observed. Therefore, the cold-tolerant CLL13 induced the sludge biolysis and compromised the negative effects of low temperature on the sludge dewatering performance, which should be beneficial for the efficient WAS biolysis treatment application in the near future under low temperature.

Trehalose can alleviate decreases in grain number per spike caused by low‐temperature stress at the booting stage by promoting floret fertility in wheat

AbstractAlleviating the negative effects of low temperature at the booting stage on wheat grain number and yield is important for maintaining high and stable wheat yields. In this study, we selected wheat varieties with different levels of cold resistance, simulated low temperature at the booting stage and exogenously applied trehalose to study its effect on wheat floret development under low‐temperature stress and explore the physiological mechanism of that process. The results showed that higher levels of endogenous trehalose benefited wheat resistance to low‐temperature stress. Exogenous trehalose inhibited floret degeneration and increased floret fertility in the apical spikelets, thus significantly alleviating the decrease in grain number per spike caused by low temperature. The results of the metabolomics analysis as well as the physiological indexes showed that trehalose significantly promoted the assimilation of nitrogen in florets under low‐temperature stress, thus reducing the accumulation of ammonium ions in the plant cells. In addition, exogenous trehalose significantly increased the endogenous spermidine level in florets, increased their glutathione and ascorbic acid contents, promoted the glutathione‐ascorbic acid cycle, and thereby reduced the contents of reactive oxygen species in florets. This may be an important physiological mechanism by which trehalose alleviates the effect of low‐temperature stress on floret development in wheat.

Identification of “bottlenecks” in the systems of adaptability in peach cultivars to specific abiotic factors limiting plant growth and development and affecting individual phases of ontogenesis to develop optimal algorithms for further breeding

Modern breeding, especially when fruit plants cultivated for decades at the same location are concerned, requires a new strategy to develop cultivars resistant to abiotic limfactors of the environment. A more in-depth analysis of genotype–environment interaction phenomena is needed, as modern studies have shown that the level of plant productivity and yields is determined not by specific “genes of quantitative traits”, but mainly by the emergent (newly occurring when a lim-factor of the environment changes at the ontogenetic and phytocenotic levels) effects of the genotype–environment interaction (GEI). New knowledge is needed about the values of contributions to the productivity of a cultivar made by each of the genetic–physiological systems of plant adaptability (GPS-ad) when exposed to a particular lim-factor of the environment at a particular phase of ontogenesis. For the first time, aiming at finding promising peach genotypes for further breeding, we studied their adaptability to low temperatures in different horticulture zones of Krasnodar Territory.Shifts in the effects of low-temperature environmental stressors in the developmental phases of cultivars (produced by climate change) were analyzed in the time interval of 1985–2018.The presence of hereditary adaptive reserves for increasing peach productivity for each phase of development in the process of studying the phenomena of GEI was disclosed. Recommendations are given to breeders on phase-to-phase breeding of future cultivars: how to protect their production process at each developmental phase from negative effects of low temperatures.

Effect of the transgenerational exposure to elevated CO2 on low temperature tolerance of winter wheat: Chloroplast ultrastructure and carbohydrate metabolism

AbstractThe transgenerational effect of elevated atmospheric CO2 concentration (e[CO2]) on low temperature response in wheat is still little investigated, through the interaction of e[CO2], and low‐temperature stress has been reported in a single generation. Here, the low temperature‐induced modifications of chloroplast ultrastructure and carbohydrate metabolism in wheat after four generations continuously grown under ambient CO2 concentration (a[CO2]) and e[CO2] (2014–2018) were investigated. The results indicated that the transgenerational exposure to e[CO2] increased the number of grana lamellae and the amounts of osmiophilic lipid droplets, attenuating the negative effect of low temperature on chloroplast ultrastructure. The transgenerational e[CO2] enhanced the activities of antioxidant enzymes (i.e. SOD, POD and CAT) and concentrations of osmotic substances (i.e. proline and soluble sugar), which alleviated the low temperature‐induced oxidative damage to the chloroplast ultrastructure. In addition, transgenerational exposure of wheat to e[CO2] increased activities of vacInv and cwInv, while decreased fructokinase activity, which affected the sucrose metabolism in wheat leaf. These findings elucidated that transgenerational exposure to e[CO2] could improve low temperature tolerance of winter wheat, which provide novel insights to the response of wheat to future climate change.

Ecological and biological assessment of climbing shrubs for landscaping residential areas

Promising types of climbing shrubs have important aesthetic and sanitary-hygienic importance as types of multi-purpose use in the development of urban and agroecosystems in arid regions (Volgograd region). The purpose of the research is to determine the prospects for the use of climbing shrubs in the vertical gardening of residential areas on chestnut soils based on the study of their biological potential. The object of research was climbing shrubs growing in the collections of the Federal Research Center for Agroecology of the Russian Academy of Sciences and in the landscaping of Volgograd and Kamyshin. In collection plantings, 5 species of different geographical origin grow: Campsis radicans; Vitis amurensis; Parthenocissus quinguefolia; Celastrus orbiculata; Lonicera caprifolium. Under the conditions of introduction, all types of climbing shrubs bloom and bear fruit. The ability of climbing shrubs to self-reproduce indicates the degree of their adaptation to new environmental conditions. Plants of all studied species reached the generative phase of development. Studies on the negative effects of low temperatures on plants in the winter showed that they are mostly frost and winter hardy and suitable for vertical gardening of residential areas of Volgograd and Kamyshin. It was revealed that climbing shrubs are quite resistant to the transfer of a complex of winter factors. North American, European and Far Eastern (Vitis amurensis, Parthenocissus quinguefolia, Celastrus orbiculata) winter the best in the collections. They have a high winter hardiness score. The area of their natural distribution is located at the same geographical latitudes as the Lower Volga. Campsis radicans freezes when lowering winter temperatures to -37°C. It has been established that the climate of the region of their natural distribution is largely similar to the area of introduction, therefore, they turned out to be quite adapted to the new growing conditions. The distribution range of the Caucasian-Mediterranean and East Asian species is much to the south. Campsis radicans and Lonicera caprifolium tolerate lower freezing temperatures worse. These species should be introduced into the southern regions of the Volgograd region. In plants at a young age and with increasing temperature and falling humidity of air and soil by the end of the growing season, the water deficit increases. The greatest water deficit during drought (July, August) as a percentage is observed in Vitis amurensis at about 22%. Celastrus orbiculata rotundifolia has a water deficit of about 18%, then Campsis radicanswithin 14%, Parthenocissus quinguefolia - 12%. The lowest water deficit is observed in Lonicera caprifolium (about 10%). Studies have shown that vertical landscaping involving climbing shrubs improves the microclimate. Wall plantings of maiden grapes in the hot summer months (July, August) reduce the air temperature by an average of 3 - 4 ° C, increase air humidity to 55 - 60% and bring microclimate parameters closer to the zone of hygienic comfort. A high yield of planting material can be achieved due to the optimal harvesting time of cuttings. The economic efficiency of production, expressed as a percentage, was 186 for Campsis radicans and 212% for Lonicera caprifolium. Вьющиеся кустарники имеют важное эстетическое и санитарно-гигиеническое значение как виды многоцелевого использования при развитии городских и агроэкосистем в засушливых районах (Волгоградская область). Объекты исследования – 5 видов вьющихся кустарников(Campsis radicans; Vitis amurensis; Parthenocissus quinguefolia; Celastrus orbiculata; Lonicera Caprifolium) в коллекциях Федерального научного центра агроэкологии Российской академии наук. Выявлено, что устойчивы к переносу комплекса зимних факторов североамериканские, европейские и дальневосточные виды (Vitis amurensis, Parthenocissus quinguefolia, Celastrus orbiculata), естественный ареал которых расположен в тех же географических широтах, что и Нижнее Поволжье. Ареал кавказско-средиземноморских и восточноазиатских видов значительно южнее. Campsis radicans и Lonicera caprifoliumрекомендуются для южных районов Волгоградской области. Установлено, что с повышением температуры и падением влажности воздуха и почвы к концу вегетации наибольший дефицит наблюдается у Vitis amurensis - 22%. Celastrus orbiculata rotundifolia–18%, Campsis radicans– 14%, Parthenocissus quinguefolia - 12%. Низкий дефицит воды у Lonicera Caprifolium (около 10%). Исследования показали, что вертикальное озеленение с использованием вьющихся кустарников улучшает микроклимат в жаркие летние месяцы.

CHARACTERISTICS OF WHEAT PLANT RESPONSES TO SHORT-TERM AND PROLONGED EXPOSURE TO SALICYLIC ACID UNDER OPTIMAL AND LOW TEMPERATURE

The effect of salicylic acid (SA, 100 μM) of various duration on some indexes of CO 2 -gas exchange, water regime, growth and cold resistance of wheat plants ( Triticum aestivum L.) under optimal (22 °C) and low hardening (4 °C) temperatures were studied. For this, week-long seedlings throughout the whole experiment (7 days) were kept on a nutrient solution with added SA at 22 and 4 °C (prolonged SA action) or kept for 1 day at 22 °C on a nutrient solution with SA and then on a solution without SA (within 6 days) exposed to temperatures of 22 and 4 °C (pre-treatment of SA). It was shown that at a temperature of 22 °C, the prolonged action of SA led to a decrease in the rate of visible photosynthesis and the ratio of respiration in the process of CO 2 -gas exchange, did not affect water use efficiency (WUE), increased the biomass of shoot and root. On the contrary, diurnal exposure to SA had virtually no effect on the dynamics of CO 2 assimilation, reduced the ratio of respiration in CO 2 -gas exchange and transpiration, but increased the WUE. At a temperature of 4 °C, the continuous action of the SA contributed to maintaining the rate of photosynthesis at a higher level than in the control, reduced the ratio of respiration in CO 2 -gas exchange, increased WUE, and also stabilized the accumulation of plant biomass. In contrast, the diurnal pretreatment of the SA increased the negative effect of low temperature on the assimilation of CO 2 , led to increase in expenses of respiration, did not affect the level of transpiration, caused a decrease in WUE. It is important, that the exogenous SA contributed to the growth of the cold tolerance of wheat in conditions of normal and low hardening temperatures. Thus, the response of wheat plants to the effect of SA depends on its duration, while the nature of changes in physiological processes differ under optimal and low temperatures.

Calcium is involved in exogenous NO-induced enhancement of photosynthesis in cucumber (Cucumis sativus L.) seedlings under low temperature

The present study explored the role of calcium ion (Ca2+) in nitric oxide (NO)-induced tolerance to low temperature in cucumber (Cucumis sativus L.) seedlings. Low temperature (11 °C/7 °C) induced a raise in NO accumulation and caused significant damages to photosynthetic processes in cucumber leaves, as evidenced by the decreased net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), chlorophyll content, maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm), maximal fluorescence (Fm) photochemical quantum yield [Y (II)], relative apparent electron transport rate (ETR), quantum yield of PSII electron transport (Fm/Fo) and latent PSII quantum yield (Fv/F0), and the increased intercellular CO2 concentration (Ci), parameters of quantum yield of regulated energy dissipation [Y (NPQ)], and quantum yield of non-regulated energy dissipation [Y (NO)]. However, exogenous sodium nitroprusside (SNP), a donor of NO, ameliorated the negative effects of low temperature. Furthermore, the content of starch, sucrose, glucose, fructose, soluble sugar and reducing sugar, as well as the transcript levels of subunit of magnesium chelatase (ChlD, ChlI, ChlH), chlorophyll a-b binding protein (Chl), original chlorophyll redox enzymes (POR) and cytochrome b6/f complex (Cytb6f) genes were elevated by the treatment with SNP alone, whereas the inhibition of Ca2+ with EGTA (Ca2+ chelating agent), LaCl3 (Ca2+ channel blocker), TFP and W-7 (calmodulin antagonists) attenuated or almost abolished the aforementioned effects of SNP under low temperature. Taken together, our findings demonstrated that Ca2+ participated in the NO-induced tolerance to low temperature by modulating the leaf gas exchange, processes of PSII, carbohydrate metabolism and expression of chlorophyll synthesis-related genes in cucumber leaves.

Investigating the effects of low temperature and compaction on the quality of adult radio-sterilised Aedes albopictus (Diptera: Culicidae) males in view of their optimal transport to the pilot sterile release site in Mauritius

The Sterile Insect Technique (SIT) is currently being investigated against Aedes albopictus Skuse (Diptera: Culicidae) mosquitoes in Panchvati, a village in Mauritius. As an essential step before field releases, this study investigated the effect of temperature (2 h exposure at 5, 10, 15 or 25 °C) and compaction (2000 males per 1062 or 8553 cm3) on the fitness of radio-sterilised Ae. albopictus males with the aim of optimising their transport from the mosquito-production unit to the release site in Panchvati. Temperature and compaction had no significant effect on male survival during the first fifteen days. However, when survival was assessed over twenty-five days, males stored at 25 °C had significantly higher survival rates than males stored at lower temperatures (Kaplan-Meier: P < 0.05). Furthermore, males stored at 5 °C survived significantly longer than those stored at 10 °C or 15 °C (Kaplan-Meier: P < 0.05). Considering the fact that a weekly release of sterile males is planned in Panchvati, the long-term negative effect of low temperatures (5 to 15 °C) on male survival, may have limited relevance in the field. Male storage at 5 °C for 2 h in compacted conditions, were hence further investigated. Compaction significantly impacted male competitiveness, with a mean competitiveness index of 0.2 when sterile males were stored at 2000 males per 1062 cm3. Two thousand males per Bugdorm cage (27,000 cm3), was found to be the optimal density at which sterile Ae. albopictus males could be stored and transported by van to Panchvati, with minimal effects of the latter’s survival and competitiveness.

Prevention of hatching of porcine morulae and blastocysts by liquid storage at 20 \xb0C

Vitrification is the ideal method for long-lasting storage of porcine embryos. However, both strict airline regulations for transport of liquid nitrogen dewars and the technical problems experienced when vitrified embryos are transferred using non-surgical procedures have led to the introduction of alternative storage methods, such as preserving embryos in liquid state. This study evaluated whether a pH-stable medium containing high concentrations of either foetal calf serum (FCS; 50%) or BSA (4%) combined with storage at temperatures of 17 °C or 20 °C maintained in vivo-derived morulae and blastocysts alive and unhatched (a sanitary requirement for embryo transportation) during 72 h of storage. Neither FCS nor BSA supplements were able to counteract the negative effect of low temperatures (17 °C) on embryonic survival after storage. At 20 °C, the protective effect of FCS or BSA depended on embryo stage. While FCS successfully arrested embryo development of only blastocysts, BSA arrested the development of both morulae and blastocysts. Over 80% of BSA arrested embryos restarted development by conventional culture and progressed to further embryonic stages, including hatching. In conclusion, porcine morulae and blastocysts can survive and remain unhatched during at least 72 h when stored at 20 °C in a BSA-containing medium.

High nitrogen input reduces yield loss from low temperature during the seedling stage in early-season rice

Early transplanting of the first crop is often attempted by farmers to increase rice yields in double-season rice cropping systems in central China. The risk of yield loss from low temperature is high with early transplanting; heavy application of nitrogen (N) fertilizer is commonly practiced to minimize this risk. However, whether the negative effects of low temperature on rice growth and yield can be mitigated by applying more N fertilizer is unclear. To address this question, we conducted field experiments on early-season rice in Wuxue county, Hubei province, China with two transplanting dates (early and normal) and two N rates (low and high) in 2016 and 2017. Transplanting was advanced by 9 days in the early compared with that in the normal transplanting date, and the high N treatment received 70 kg ha−1 more basal N than did the low N treatment. Early transplanting reduced the grain yield of early-season rice by 20.1% in 2016 and by 7.0% in 2017 at the low N rate, but there was no difference in grain yield between transplanting dates at the high N rate in both years. The high N rate increased the grain yield of early transplanting by 21.9%, averaged across the two years. Both the reduction in grain yield due to early transplanting and the increase in grain yield due to the high N rate under early transplanting were explained by the number of spikelets m-2 and dry weight production. The high N rate promoted N uptake, tillering, and leaf area development under low temperature. Thus, we conclude that the negative effects of low temperature on early-season rice can be mitigated by applying more basal N fertilizer. Environmental concerns about the practices of early transplanting and heavy basal N application for early-season rice are discussed.

Ripening Recovery and Sensory Quality of Pink Tomatoes Stored in Controlled Atmosphere at Chilling or Nonchilling Temperatures to Extend Shelf Life

Harvesting before ripening initiation (i.e., mature green) may negatively affect the flavor of fresh tomatoes (Solanum lycopersicum) even though the ripening process off the vine is physiologically the same as that on the plant. Low temperature storage at or below the putative chilling injury (CI) threshold can also have detrimental effects on fresh tomato flavor regardless of the developmental stage of the fruit at harvest, but sensitivity to CI declines with ripening. Controlled atmospheres (CA) using reduced oxygen and elevated carbon dioxide partial pressures can extend the shelf life (SL) of tomatoes while possibly minimizing the negative effects of low temperatures. In this study, we explored the possibility that a combination of temperature and CA could be used to achieve similar SL for pink-harvested tomatoes as has been found in other studies with green-harvested fruit while avoiding the negative effects of CI on sensory quality. Consumer panels were given samples of pink-harvested tomatoes after they had reached the red ripeness stage in terms of surface hue following storage for 7 days in air or CA at 7.5, 15, or 20 °C followed by 2–7 days ripening in air at 20 °C. Exposing pink tomatoes to 7.5 °C before ripening to the full-red stage at 20 °C negatively affected fruit sensory quality, holding fruit constantly at 20 °C until they reached the full-red stage resulted in better quality for one taste panel, whereas there was no difference in another taste panel. The time to reach the full-red stage was extended by CA. Sensory quality of air- and CA-stored fruit was similar at the nonchilling temperatures of 15 and 20 °C. Pink stage tomato fruit stored in CA at 7.5 °C for 7 days did not attain full red color within the subsequent 7 days in air at 20 °C.

Herbicide isoproturon aggravates the damage of low temperature stress and exogenous ascorbic acid alleviates the combined stress in wheat seedlings

Herbicides are largely used to control weed growth in wheat production. However, the application of some kind of herbicides usually aggravates the damage caused by low temperature, and is also a very common adversity during the early growth stages of wheat. In this study, we pre-treated wheat seedlings with the herbicide chemicals of isoproturon, fluroxypyr and fenoxaprop-P-ethyl, respectively and then exposed the plants to low temperature stress with different time intervals. The herbicides, especially isoproturon, significantly increased the negative effects of low temperature on electron transport rate, chlorophyll content, cell membrane stability as well as growth of wheat plants. Furthermore, the foliar application of ascorbic acid (AsA) decreased relative electric conductivity, reduced the content of malondialdehyde, and reduced the production rate of reactive oxygen species, these were in line with elevated activities of superoxide dismutase, catalase and peroxidase under the combined stress of isoproturon and low temperature, indicating that AsA effectively mitigated the sever oxidative stress induced by the combined stresses. Thus, some of the herbicides such as isoproturon are suggested to be very carefully used before the possibility of low temperature events. In case low temperature stress occurs after using of isoproturon, AsA could be used to partially alleviate the damage by the combined stress of isoproturon and low temperature in wheat production.

Effects of low temperatures on the survival and development of Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) under different storage durations

Azuki bean weevil, Callosobruchus chinensis L. is a cosmopolitan pest of stored grain legumes. Larvae cause huge losses of energy and seeds in the storage. This study assessed the effects of short-term exposure to low-temperatures (4, 0, and −4°C) under seven durations of storage (1, 5, 10, 15, 20, 25, and 30days) on the survival, development, and adult performance of C. chinensis in laboratory. The effects were studied on three life stages (egg, larva [2–3 instar], and pupa) of C. chinensis. The results showed that low-temperature treatments have significant effects on the life variables of C. chinensis. Among the stages, egg and pupa stages were most sensitive to low-temperature. The very low survival rates of eggs at −4°C, no pupa stages of C. chinensis survived after 10days storage. Cold exposure at −4°C for <10days not only increased egg and pupa mortality, but the negative effects also transmitted to the larvae and pupa developed from those eggs (64.3days) and least adults were emerged with minimum longevity. Increasing the duration of cold exposure further reduced survival rates, e.g. about 20% of the eggs survived after 15days exposure at −4°C, but <30% of them survived after 25days treatment at 4 and 0°C. Low-temperature treatments have also affected on the adult performances such as adult weight. However, there were not any negative effects of low-temperatures on the seed germination. The life variables of C. chinensis are discussed in terms of targeting particular susceptibilities to low-temperatures in different durations of storage as an alternative to chemical treatments.