Carbohydrate Reserves Research Articles

Hypometabolic strategy and glucose metabolism maintenance of Aedes aegypti egg desiccation

The mosquito Aedes aegypti is vector of several viruses including yellow fever virus, dengue virus chikungunya virus and Zika virus. One of the major problems involving these diseases transmission is that A. aegypti embryos are resistant to desiccation at the end of embryogenesis, surviving and remaining viable for several months inside the egg. Therefore, a fine metabolism control is essential to support these organisms throughout this period of resistance. The carbohydrate metabolism has been shown to be of great importance during arthropod embryogenesis, changing dramatically in order to promote growth and differentiation and in periods of resistance. This study investigated fundamental aspects of glucose metabolism in three stages of A. aegypti egg development: pre-desiccated, desiccated, and rehydrated. The activities of regulatory enzymes in carbohydrate metabolism such as pyruvate kinase, hexokinase and glucose 6-phosphate dehydrogenase were evaluated. We show that these activities were reduced in A. aegypti desiccated eggs, suggesting a decreased activity of glycolytic and pentose phosphate pathway. In contrast, gluconeogenesis increased in desiccated eggs, which uses protein as substrate to synthesize glucose. Accordingly, protein amount decreased during this stage, while glucose levels increased. Glycogen content, a major carbohydrate reserve in mosquitoes, was evaluated and shown to be lower in desiccated and rehydrated eggs, indicating it was used to supply energy metabolism. We observed a reactivation of carbohydrate catabolism and an increased gluconeogenesis after rehydration, suggesting that controlling glucose metabolism was essential not only to survive the period of desiccation, but also for subsequent larvae hatch. Taken together, these results contribute to a better understanding of metabolism regulation in A. aegypti eggs during desiccation periods. Such regulatory mechanisms enable higher survival rate and consequently promote virus transmission by these important disease vectors, making them interesting subjects in the search for novel control methods.

Trees use more non-structural carbohydrate reserves during epicormic than basal resprouting.

Non-structural carbohydrates (NSCs) are crucial to support tree resprouting after disturbances that damage the crown or stem. Epicormic resprouting (from stem) could demand more from NSC reserves than basal resprouting (following top-kill), since epicormically resprouting trees need to maintain a greater living biomass. Yet, little is known about NSC use during epicormic resprouting, particularly the relative importance of stem and below-ground NSC reserves. We compared the distribution and magnitude of NSC decreases during epicormic and basal resprouting by experimentally removing crowns or stems of 14-year-old Eucalyptus obliqua L'Hér. trees in native forest, then harvesting these trees over a 10-month period (start, sprouts emerged, sprouts expanded) to measure changes in NSC concentration and mass by organ (stem, lignotuber, roots). We hypothesized that (i) NSC depletion during resprouting is primarily due to decreases in starch rather than soluble sugars concentrations; (ii) during epicormic resprouting, stem NSC concentrations are decreased irrespective of any decreases in roots; and (iii) absolute decreases in NSC mass are greater for epicormic than basal resprouting during the leafless period due to the carbon demands associated with maintaining greater living biomass. Results confirmed our hypotheses; starch was the primary storage carbohydrate, stems were an important source of starch during epicormic resprouting and carbon demands of maintenance functions were greater for epicormic resprouting, leading to greater decreases in NSC reserves. Roots were a more important starch storage organ than the lignotuber for both epicormic and basal resprouting. The proportional decrease in starch was severe for both modes of resprouting due to a long leafless period, after which trees resprouting epicormically relied on starch reserves for longer than those resprouting basally. It remains to be seen how the timing of disturbance affects the timing and vigour of resprouting, and how long-term NSC recovery differs for epicormic and basal resprouting.

No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

AbstractTemperate forests are predicted to experience an increased frequency and intensity of climate change‐induced summer droughts and heat waves in the near future. Yet, while previous studies clearly showed a high drought sensitivity of different temperate tree species, the vulnerability of the physiological integrity of these trees remains unclear.Here, we assessed the sensitivity of six temperate tree species to severe water limitation during three consecutive growing seasons, including the exceptional 2015 central European summer drought and heat wave. Specifically, we assessed stem increment growth, sap flow, water potentials, hydraulic vulnerability, and nonstructural carbohydrate contents in leaves and branches to determine how mature temperate trees responded to this exceptional weather event and how the observed responses relate to variation in xylem embolism and carbohydrate economy.We found that the trees' predawn water potentials reached their minimum values during the 2015 summer drought and most species reduced their sap flow by up to 80%. Also, increment growth was strongly impaired with the onset of the drought in all species. Despite the strong responses in the trees' growth and water relations, all species exhibited minimum midday shoot water potentials well away from values associated with severe embolism (P50). In addition, we detected no distinct decrease in nonstructural carbohydrate contents in leaves, bark, and stems throughout the drought event.Synthesis. This study shows that mature individuals of six common central European forest tree species strongly reacted to a severe summer drought by reducing their water consumption and stopping growth. We found, however, no indications for xylem embolism or carbohydrate depletion in these trees. This suggests, that xylem embolism formation and carbohydrate reserve depletion are not routine in temperate trees during seasonal strong drought and reveals a low vulnerability of the physiological integrity of temperate trees during drought events as we describe here.

Metabolomics reveals the key role of oxygen metabolism in heat susceptibility of an alpine-dwelling ghost moth, Thitarodes xiaojinensis (Lepidoptera: Hepialidae).

Ghost moths inhabiting the alpine meadows of the Tibetan Plateau are cold-adapted stenothermal organisms that are susceptible to heat (dead within 7 days at 27°C exposure). Exploring the metabolic basis of their heat susceptibility would extend our understanding of the thermal biology of alpine-dwelling invertebrates. Here, gas chromatography-mass spectrometry-based metabolomics was combined with physiological and transcriptional approaches to determine the metabolic mechanisms of heat susceptibility in Thitarodes xiaojinensis larvae. The metabolomics results showed that 27°C heat stress impaired the Krebs cycle and lipolysis in T. xiaojinensis larvae, as demonstrated by the accumulation of intermediary metabolites. In addition, carbohydrate reserves were highly and exclusively consumed, and an anaerobic product, lactate, accumulated. This evidence suggested a strong reliance on glycolysis to anaerobically generate energy. The respiration rate and enzymatic activity test results indicated a deficiency in O2 metabolism; in addition, the Krebs cycle capacity was not decreased, and the metabolic flux through aerobic pathways was limited. These findings were further supported by the occurrence of hypoxia symptoms in midgut mitochondria (vacuolation and swelling) and increased transcription of hypoxia-induced factor 1-α. Overall, heat stress caused O2 limitation and depressed the overall intensity of aerobic metabolism in ghost moths, and less efficient anaerobic glycolysis was activated to sustain their energy supply. As carbohydrates were depleted, the energy supply became deficient. Our study presents a comprehensive metabolic explanation for the heat susceptibility of ghost moths and reveals the relationship between O2 metabolism and heat susceptibility in these larvae.

The ER - Glycogen Particle - Phagophore Triangle: A Hub Connecting Glycogenolysis and Glycophagy?

Glycogen particle is an intracellular organelle, which serves as a carbohydrate reserve in various cells. The function of glycogen is not entirely known in several cell types. Glycogen can be mobilized for different purposes, which can be related to cellular metabolic needs, intracellular redox state, metabolic state of the whole organism depending on regulatory aspects and also on cell functions. Essentially there are two different ways of glycogen degradation localized in different cellular organelles: glycogenolysis or lysosomal breakdown by acid alpha-glucosidase. While glycogenolysis occurs in glycogen particles connected to endoplasmic reticulum membrane, glycogen particles can be also combined with phagophores forming autophagosomes. A subdomain of the endoplasmic reticulum membrane - omegasomes - are the sites for phagophore formation. Thus, three organelles, the endoplasmic reticulum, the phagophore and the glycogen particle forms a triangle in which glycogen degradation occurs. The physiological significance, molecular logic and regulation of the two different catabolic paths are summarized and discussed with special aspect on the role of glycogen particles in intracellular organelle homeostasis and on molecular pathology of the cell. Pathological aspects and some diseases connected to the two different degradation pathways of glycogen particles are also detailed.

Effect of Seasonal Variations and Growth Conditions on Carbohydrate Partitioning in Different Organs and the Quality of Bush Tea

Bush tea (Athrixia phylicoides DC.) is a root perennial shrub used as indigenous tea and medicinal tea in South Africa. Thus, concurrent trials were conducted under different growing conditions as follows: in the glasshouse, field planted and wild, naturally grown, to investigate the effects of seasonal harvests and growing environments on carbohydrate reserves and quality parameters of bush tea. Of 50 plants, 25 single plants were allotted to each respective environment in a field and glasshouse conditions—and were arranged in a randomized complete block design. These were then harvested in summer, autumn, winter, and spring, respectively. For the wild bush tea trial, 25 single plants were randomly selected. Selected sugars and starch were quantified together with other quality parameters [total polyphenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC), and total antioxidant activities). The study revealed that the glucose content of bush tea plant organs was significantly higher during winter, followed by autumn, as compared with the other seasons. Similar fructose and sucrose trends were evident. However, the content of amylopectin was also significantly higher during summer, followed by autumn, compared with the other seasons. In winter, plants exhibited higher amylopectin content when compared with other seasons. No significant differences were found in the amylose content. Both wild and cultivated bush tea plants yielded the highest specific sugars in the study. The phytochemicals present in the leaves of field-grown bush tea and wild bush tea during winter were higher than in those grown in summer, autumn, and spring. No significant difference in tannin contents was observed, irrespective of seasons and growing conditions. Regardless of growing conditions, autumn yielded lower total antioxidant activities using both the DPPH and ferric reducing antioxidant power (FRAP) assays when compared with other seasons. To better resolve the metabolomic data, principal component analysis (PCA) was used and the first principal component showed a strong correlation within all parameters recorded over PC2. Future ecophysiological studies are recommended to establish region- and season-specific metabolomic biomarkers with canonical distinction on beverage, pharmacological, and organoleptic attributes of bush teas.

Enhanced stolon growth and metabolic adjustment in creeping bentgrass with elevated CO2 concentration

Stolon growth and proliferation are highly desirable traits for stoloniferous plant species. The objectives of this study were to elucidate the effects of elevated CO2 on stolon growth in a stoloniferous perennial grass species, creeping bentgrass (Agrostis stolonifera), and identify metabolites and associated metabolic pathways for CO2-regulation of stolon growth under well-watered and drought conditions. Plants were grown under either ambient CO2 concentration at 400 μmol mol−1 or elevated CO2 concentration at 800 μmol mol−1 and subjected to well-watered control or drought stress by withholding irrigation in growth chambers. Elevated CO2 led to increased number of stolon internodes and stolon length, and mitigated drought damages to creeping bentgrass, as manifested by the increased leaf relative water content and reduced electrolyte leakage. Elevated CO2 increased stolon content of metabolites involved in carbohydrate reserves, respiratory metabolism, and membrane maintenance, including maltose, mannobiose, galactinol, 5-oxoproline, galacturonic acid, glycolic acid, gluconic acid, isoferulic acid, citric acid, threonic acid, lactic acid, succinic acid, and linolenic acid and linoleic acid. The CO2-reponsive metabolites for carbohydrate reserves, respiratory metabolism, and membrane maintenance could contribute to the enhanced stolon growth, thereby potentially facilitating rapid stand establishment and increasing shoot biomass production in perennial grass species.

Effect of leaf removal on grape and wine composition in ‘Merlot’

The adaptation to climate change requires the adjustments of viticultural practices, particularly changing the fruit to leaf area ratio which could be an effective option to maintain and enhance fruit and wine quality. Fruiting capacity and berry composition of grapevine are dependent on canopy area, with grapevine carbohydrate reserves affected by the crop load. 'Merlot' grapevines grown in the experimental vineyard of the NWGIC (South Eastern Australia) received treatments that altered the leaf area/fruit ratio. These received severe summer pruning (SSP), upper (ULR) and lower leaf removal (LLR) implemented at pea size during two growing seasons. Generally, all treatments lowered total soluble sugars, but the total sugar yield was not altered, also the total anthocyanins and phenolics of the berries did not differ at harvest. The titratable acidity and alcohol concentration of the wine was influenced by the change of the canopy size as were sensory attributes. Particularly, wines made from grapes of the SSP treatment were different in most attributes compared to wines that were made from grapes of untreated vines. The overall response of partial defoliation and severe summer pruning conducted prior to veraison suggests that it can be used as a management practise to alter berry ripening speed and grape composition, consequentially influencing wine attributes. However, depending on position, intensity and time the impact of such treatments on carbohydrate reserves in the perennial structure may have long-term implications.

The application of ohmic heating for inulin extraction from the wet-milled and dry-milled powders of Jerusalem artichoke (Helianthus tuberosus L.) tuber

Abstract In this study, ohmic heating was applied for inulin extraction from the Jerusalem artichoke tuber (JAT). Raw materials for extraction were prepared by two different schemes comprising milling the blanched JAT slices and water mixture (wet milling) and grinding the dried JAT to be powder before mixing water (dry milling). Also, the inulin extracts were evaporated using a rotary evaporator and then spray-dried to be inulin powder. The main objectives were (1) to investigate the effects of applying ohmic heating on the extraction yield and quality of inulin extracts in comparison with conventional method and (2) to determine the suitable preparation method by comparing between wet and dry milling. The results indicated that the electrical conductivities of JAT solutions prepared from the wet-milled and dry-milled powders were 0.121–0.200 and 0.123–0.247 S/m respectively. The inulin extraction applying ohmic heating resulted in the significantly higher yield than conventional heating. Furthermore, the sample preparation using dry milling provided the higher extraction yield and inulin purity than that of wet milling. The scanning electron micrographs illustrated that in overall the dry-milled JAT samples were more porous and finer than the wet-mill samples. The inulin purity of the powder product obtained from the production with dry milling and ohmic method was about 57.29 g/100 gdry mass while its production yield was 17.59% which was rather low due to the loss of solids occurring in the blanching, extraction and spray drying processes. Industrial relevance Jerusalem artichoke (Helianthus tuberosus L.) has been widely cultivated in many countries. Jerusalem artichoke tubers (JAT) accumulates inulin as a main carbohydrate reserve; hence, it has high potential to be raw material for inulin powder production. Nowadays, inulin is generally used by the food and beverage industries as a soluble dietary fiber, prebiotic and fat or sugar replacer. The extraction is a crucial process for producing inulin powder from JAT. The result of this work revealed that ohmic heating method provided higher inulin extraction yield than conventional heating method. Furthermore, the sample preparation using dry milling provided the higher extraction yield and inulin purity than that of wet milling. This information is vital for the inulin powder manufacturers to make a decision for their production facility concept and design.

Responses of planted Populus tremuloides seedlings to grass competition during early establishment

Root systems of aspen seedlings display limited architectural plasticity in response to below-ground competition, but seedlings compensate for restricted rooting space and reduced root system size, by optimizing water uptake. Below-ground competition with grasses often plays a critical role during tree seedling establishment, but many underlying mechanisms are not well understood. We used a controlled field experiment to study how trembling aspen (Populus tremuloides Michx.) seedlings compete with smooth brome grass (Bromus inermis L.) for space during the first 3 years of seedling establishment and how it affected aspen seedling development. Our study showed that competition with grasses had a limited impact on architectural plasticity of aspen seedlings. Seedlings faced with competition from smooth brome were overall smaller and most architectural parameters, with the exception of shoot height, appeared simply scaled down proportionally. Shoot height changed less than other parameters, because aspen competing with grass allocated relatively more carbon to shoots than roots and adopted a slender shoot morphology to quickly overtop the competition. Aspen growing with grass competition had significantly smaller root systems. Both lateral extent and maximum rooting depth were reduced by ~ 50%. In response to the restricted rooting space, roots of aspen seedlings faced with grass competition had a lower specific root length. Root carbohydrate reserves were not affected by competition; however, aspen roots growing with grass competition had higher soluble sugar concentrations which may be associated with the observed three times higher water uptake efficiency per unit root biomass. Our findings suggest that aspen seedlings have limited capacity for architectural plasticity in response to root competition, but are at least temporarily able to compensate for reduced root system size and rooting space, by optimizing water uptake efficiency.

Carbohydrate reserves and seed development: an overview.

Seeds are one of the most important food sources, providing humans and animals with essential nutrients. These nutrients include carbohydrates, lipids, proteins, vitamins and minerals. Carbohydrates are one of the main energy sources for both plant and animal cells and play a fundamental role in seed development, human nutrition and the food industry. Many studies have focused on the molecular pathways that control carbohydrate flow during seed development in monocot and dicot species. For this reason, an overview of seed biodiversity focused on the multiple metabolic and physiological mechanisms that govern seed carbohydrate storage function in the plant kingdom is required. A large number of mutants affecting carbohydrate metabolism, which display defective seed development, are currently available for many plant species. The physiological, biochemical and biomolecular study of such mutants has led researchers to understand better how metabolism of carbohydrates works in plants and the critical role that these carbohydrates, and especially starch, play during seed development. In this review, we summarize and analyze the newest findings related to carbohydrate metabolism's effects on seed development, pointing out key regulatory genes and enzymes that influence seed sugar import and metabolism. Our review also aims to provide guidelines for future research in the field and in this way to assist seed quality optimization by targeted genetic engineering and classical breeding programs.

Spruce shows greater sensitivity to recent warming than Douglas‐fir in central British Columbia

AbstractThe effects of climate change on tree growth in ecosystems limited by cold temperature remain unclear. In some cases, growth may increase, but because warmer temperatures can increase water stress, growth may also decline. As climate changes in the sub‐boreal spruce (SBS) zone in central British Columbia, hybrid white spruce (Picea engelmannii × glauca)—a dominant but drought‐intolerant species of this region—is predicted to decline over much of its range, while species such as Douglas‐fir (Pseudotsuga menziesii var. glauca) are likely to replace spruce. To see whether these shifts are already evident, we examined recent trends in basal area increment (BAI) of these two species over the past 50 yr (1961–2010) and explored relationships with climate variables in the SBS zone across a range of sites varying in water availability due to differences in climate and soil moisture regimes. In addition, we analyzed wood δ13C during this period and root carbohydrate reserve (NSC) concentrations at the end of this period as indicators of water and carbon stress, respectively, to help interpret growth trends and climate relationships among sites. Spruce BAI was negatively associated with spring and/or summer temperature on all sites, but growth was never negatively correlated with temperature in Douglas‐fir. For both species, lower BAI on the driest site was accompanied by higher δ13C and lower root NSC reserve concentrations, particularly starch, consistent with drought stress reducing water and carbon availability for growth. However, there was no indication that the negative growth response to temperature was more pronounced on drier sites, as the only growth decline in spruce occurred on a mesic site with lower δ13C. We conclude that rising temperatures are likely to negatively impact the growth of spruce more than Douglas‐fir in the SBS zone, supporting predictions that spruce will decline and be replaced by other species like Douglas‐fir. And while rising temperatures may have already reduced growth on some sites, these declines are not clearly related to increasing drought stress but may relate to effects on the timing of snowmelt.

Response to Selection for Grain Filling Capacity in Wheat (Triticum aestivum L.) under Heat Stress

Improving tolerance to heat stress of bread wheat has been achieved through enhancing grain filling capacity by two cycles of selection imposed on five F2 populations derived from crosses among long spike–equally tall inbred lines quite variable in 1000 kernel weight (1000 KW). The first cycle was a divergent selection for 1000 KW conducted under the high temperature of a late rowing date at an intensity of 5% and the responses were measured in favorable and heat stress environments. Significant positive responses were obtained in the five populations in the two contrasting environments. Selection for higher 1000 KW resulted in greater response under heat stress (averaged 6.9% of population mean) than under favorable conditions (averaged 4.92%). The F3 families selected for higher 1000 KW were less sensitive to high temperature as they displayed less reductions due to heat stress (averaged 5.55%) than the unselected bulks (7.14% average reduction) relative to the performance under favorable conditions. The responses to selection for lower 1000 KW were greater under the favorable conditions (averaged 5.6%) than under heat stress (averaged 4.12%). Significant concurrent positive responses were obtained in stem diameter with selection for higher 1000 KW which was greater under heat stress (averaged 8.82%) than under favorable conditions (averaged 4.51%). Directional selection for stem diameter imposed on the plants of the F3 families in the second cycle resulted in significant positive responses in the five populations which averaged 16.24% of population mean as well as concurrent responses in 1000 KW (averaged 16.01%) and in grain yield /spike (averaged 19.5%). Selection for 1000 KW under heat stress produced concurrent response in stem diameter and vice versa which implies that the two characters are closely related. Increasing stem diameter by selection was more efficient than selection for 1000 KW in enhancing grain filling capacity through providing greater storage of stem reserves of water soluble carbohydrates to be remobilized into the developing grains under high temperature.

Effect of soil salinity on fructan content and polymerization degree in the sprouting tubers of Jerusalem artichoke (Helianthus tuberosus L.)

In addition to their role as reserve carbohydrates, fructans have been recognized as compounds that are protective against adverse environments. The aim of this study was to identify changes in the content and the degree of polymerization (DP) of fructan in sprouting tubers of Jerusalem artichoke under salt stress. Fructan was extracted from tubers at 1, 3, 5, and 7 days after planting in sandy loam soil irrigated with NaCl solution. Fructan accumulation and polymerization and the expression of genes encoding enzymes for fructan synthesis and degradation were evaluated. No significant differences between the control and treatment groups were observed until 5 days after sowing. The highest level of salinity (250 mM) not only inhibited sprouting and root growth but also decreased the level of fructan in the tubers. The proportion of fructan at DP 2–5 rapidly increased one day after sowing and then decreased over time. Under various NaCl treatments, at 7 days after sowing, all fructans except fructan at DP 6–10 were present in proportions less than or equal to the control. The variation in the DP of fructan was related to the transcription level of fructan metabolism genes. Fructan may support sprouting or resistance to salt stress by changing the DP of fructan molecules through hydrolysis without changing the total amount of fructan. The low-molecular-weight oligosaccharides (DP < 5) may be the major carbohydrates that support tuber sprouting or that are involved in protection from salt stress.

Successful Colonization of Lodgepole Pine Trees by Mountain Pine Beetle Increased Monoterpene Production and Exhausted Carbohydrate Reserves.

Lodgepole pine (Pinus contorta) forests have experienced severe mortality from mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins) in western North America for the last several years. Although the mechanisms by which beetles kill host trees are unclear, they are likely linked to pine defense monoterpenes that are synthesized from carbohydrate reserves. However, how carbohydrates and monoterpenes interact in response to MPB colonization is unknown. Understanding this relationship could help to elucidate how pines succumb to bark beetle attack. We compared concentrations of individual and total monoterpenes and carbohydrates in the phloem of healthy pine trees with those naturally colonized by MPB. Trees attacked by MPB had nearly 300% more monoterpenes and 40% less carbohydrates. Total monoterpene concentrations were most strongly associated with the concentration of sugars in the phloem. These results suggest that bark beetle colonization likely depletes carbohydrate reserves by increasing the production of carbon-rich monoterpenes, and other carbon-based secondary compounds. Bark beetle attacks also reduce water transport causing the disruption of carbon transport between tree foliage and roots, which restricts carbon assimilation. Reduction in carbohydrate reserves likely contributes to tree mortality.

Effect of trophic support on the dynamics of growth processes and carbohydrate content of winter wheat sprouts under vernalization

The influence of contrasting conditions of trophic support of vernalization on the growth reaction and dynamics of the content of various fractions of soluble carbohydrates of sprouts of two winter wheat varieties Statna and Doridna were studied. In experiments, the contrasting trophic conditions of vernalization were created by adding 3% sucrose solution, as well as isolation of endosperm, a natural reserve of carbohydrates and biologically active substances. It was shown that optimal conditions of trophic support (integral seeds + water) determined the maximum linear growth and accumulation of sprouts biomass during vernalization. The excess of exogenous sugars (integral seeds + 3% sucrose solution) inhibited growth processes. However, the deficit of trophic factors (isolated buds + 3% sucrose solution) also inhibited growth and the lack of trophic support (isolated buds + water) completely inhibited growth and accumulation of sprouts biomass during 45 days of vernalization. It was established that the dynamics of changes in soluble carbohydrates content in winter wheat sprouts also depended on the trophic support level of vernalization and correlated with changes of growth reaction. It was shown the oligosaccharide content was significantly higher than monosaccharide content of sprouts of all the variants of both varieties during the entire period of vernalization. In view of the fact that monosaccharides are the most metabolically active carbohydrates, they are probably spent as much as possible at the first stages of vernalization (15–30 days). It is discussed that different level of trophic support is able to be one of the important factors of genetic and/or epigenetic regulation of Triticum aestivum L. Thus, changes in metabolic processes, in particular carbohydrate metabolism, can effect on the reduction of VRN genes expression, which are the target of epigenetic regulation, and as a result, on the ability of soft wheat plants to flower. It is assumed that the regulatory role of carbohydrates in vernalization process can be realized only at the optimal level of trophic support.

Seasonal patterns of nonstructural carbohydrate reserves in four woody boreal species1

Plants store nonstructural carbohydrates (NSCs), such as sugars and starch, to use as carbon and energy sources for daily maintenance and growth needs as well as during times of stress. Allocation of NSCs to storage provides an important physiological strategy associated with future growth and survival, and thus understanding the seasonal patterns of NSC reserves provides insight into how species with different traits (e.g., growth form, leaf habit, wood anatomy) may respond to stress. We characterized the seasonal patterns of NSCs in four woody boreal plant species in Minnesota, USA. Sugar and starch concentrations were measured across the year in the roots and branches of two conifer trees, black spruce (Picea mariana (Mill.) B.S.P.) and eastern tamarack (Larix laricina (Du Roi) K. Koch), as well as in the leaves and branches of two evergreen broadleaf shrubs, bog Labrador tea (Rhododendron groenlandicum (Oeder) Kron & Judd) and leatherleaf (Chamaedaphne calyculata (L.) Moench). In general, seasonal variation was dominated by changes in starch across all organs and species. While similar seasonal patterns of NSCs were observed in the shrubs, different seasonal patterns were observed between the trees, particularly in the roots. Our results suggest that species-specific traits likely have consequences for organ-level storage dynamics, which may influence whole-plant growth and survival under global change.

Genetic and biochemical analysis of the reserve carbohydrate metabolism in Candida albicans and Candida rugosa

Genetic and biochemical analysis of the reserve carbohydrate metabolism in Candida albicans and Candida rugosa

Late season mineral foliar application improves nutritional reserves and flowering of kiwifruit

Abstract Proper management of late season mineral nutrition in kiwifruit orchards is necessary to maintain sufficient carbohydrate and mineral reserves for efficient growth and yield in the following season. The present study was conducted in order to investigate the influence of urea (0.25%, 0.5% and 1%), zinc sulfate (1000, 1500 and 2000 mg l−1) and boric acid (500, 1000 and 1500 mg l−1) foliar application, both alone and combined, on physiological and biochemical characteristics and mineral nutrients concentration in leaf and bud tissues and, flowering of kiwifruit cv Hayward in Guilan, Iran during two years. In order to determine the best application time in late season, foliar application was applied at three different times: September 17, October7 and October 28. Leaf and bud samples were collected three weeks after the last foliar application. Although combined foliar application of urea (1%), zinc sulfate (2000 mg l−1) and boric acid (1500 mg l−1) significantly increased leaves chlorophyll concentration and boron, zinc, soluble carbohydrate and starch content of leaf and bud tissues in the fall, however this consistent elevation in almost all measured parameters was not found in other experimental fertilization treatments compared to control vines. Likewise, bud break, and flowering shoot percentage, and total number of flowers and abnormal flowers percentage was significantly improved in the following growth season by urea (1%), zinc sulfate (2000 mg l−1) and boric acid (1500 mg l−1) treatment in comparison with control group. There were no significant differences among the treated and non-treated vines regarding shoots growth, leaf abscission and the beginning of winter rest of the kiwifruit vines. Considering all measured parameters, we conclude October 28 was the best spraying time. These results suggest that urea (1%), zinc sulfate (2000 mg l−1) and boric acid (1500 mg l−1) treatment on October 28 can be used as a proper way to improve mineral and carbohydrate reserves of kiwifruit orchards to use in next growing season.

Stored root carbohydrates can maintain root respiration for extended periods.

Tight coupling between below-ground autotrophic respiration and the availability of recently assimilated carbon (C) has become a paradigm in the ecophysiological literature. Here, we show that stored carbohydrates can decouple respiration from assimilation for prolonged periods by mobilizing reserves from transport roots to absorptive roots. We permanently disrupted the below-ground transfer of recently assimilated C using stem girdling and root trenching and measured soil CO2 efflux for over 1 yr in longleaf pine (Pinus palustris), a species that has large reserves of stored carbohydrates in roots. Soil CO2 efflux was not influenced by girdling or trenching through the 14-month observation period. Stored carbohydrate concentrations in absorptive roots were not affected by the disrupted supply of current photosynthate for over 1 yr; however, carbohydrate concentrations in transport roots decreased. Our results indicate that root respiration can be decoupled from recent canopy assimilation and that stored carbohydrates can be mobilized from transport roots to absorptive roots to maintain respiration for over 1 yr. This refines the current paradigm that canopy assimilation and below-ground respiration are tightly coupled and provides evidence of the mechanism and dynamics responsible for decoupling the above- and below-ground processes.