Non-structural Carbohydrate Metabolism Research Articles

The Application Timing of a Cytokinin B-Mo-based Product Affects the Characteristics of Rooted Cuttings and Nonstructural Carbohydrates of Coleus (Plectranthus scutellarioides cv. Wild Lime) during Adventitious Root Development

A large group of horticulture species are propagated vegetatively through shoot-tip cuttings harvested from stock plants and planted to form adventitious roots. Adventitious rooting leads to establishing a carbohydrate sink in the region of root regeneration that is highly dependent on energy and carbon skeletons. We hypothesized that the timing of exogenous applications of cytokinin (CK) and boron (B)–molybdenum (Mo)-based products during adventitious root development can affect the flow of sugars from leaves to sinks, carbon allocation to the adventitious roots, and the quality of rooted cuttings. During this project, we aimed to determine if the application time of a CK/B-Mo-based product during the adventitious root development of unrooted cuttings would impact the source-to-sink relationship and, hence, affect plug growth and quality. A sink-strengthening commercial product based on cytokinin, B, and Mo was applied at four plug development stages plus a negative control as follows: T1, plants without product (control); T2, sticking stage (starting 24 hours after the sticking); T3, callus formation stage; T4, root development stage; and T5, toning stage. The root and shoot lengths and dry matter, number of leaves, leaf chlorophyll content, root-to-shoot ratio (based on dry matter), and nonstructural carbohydrate contents were measured. The timing of the application of the product impacted the root development, quality of the cuttings, and nonstructural carbohydrate content. Product application during the adventitious root dedifferentiation and induction phases (T2) resulted in the shortest root and shoot lengths, lowest dry matter accumulation, lowest nonstructural carbohydrate contents, and some phytotoxicity. Application during the initiation phase (T3) resulted in greater root length, total dry matter, and total soluble sugar contents compared with the control. Application during the expression phase (T4) resulted in the largest root length and mass and the highest sucrose contents. Applying the product when the roots had grown and reached all the edges of the growing media (T5) did not have any benefits compared with the control. This study provides new insights into the application timing of exogenous CKs, B, and Mo to generate a well-toned rooted coleus cutting and potential explanations in relation to nonstructural carbohydrate metabolism.

Emerging Insights into the Roles of the Rhizome-Culm System in Bamboo Shoot Development through Analysis of Non-Structural Carbohydrate Changes.

Non-structural carbohydrates (NSCs) required for bamboo shoot development, the critical stage that determines the yield of a bamboo stand, originate from the parent bamboo with the complex underground system. However, the metabolic mechanism of NSCs in the rhizome-culm system during bamboo shoot development remains unclear. In this study, we focused on the changes of NSCs in the rhizome-culm system and used anatomical, physiological, and biochemical methods to investigate the metabolism of NSCs in bamboo shoots of Phyllostachys edulis and the role of NSCs supply in the parent bamboo at different ages. The results showed that NSCs were accumulated and consumed from the bottom to the top in a bamboo shoot, which was consistent with the developmental pattern. The starch granules were stored in advance. The bamboo sheath stored starch from the dormant stage of shoot buds. The functions of culms and rhizomes showed age-dependent differences. Adult culms showed the highest capacity to provide NSCs, with more stored NSCs and higher β-amylase activity. Conversely, young culms seemed to prefer their growth, while old culms tended to store starch. Accordingly, adult rhizomes preferred sugar transport due to the lowest starch storage, lower ADP-glucose pyrophosphorylase (AGPase) activity, and higher β-amylase activity, while young and old rhizomes tended to prefer starch storage. These results provide a basis for further understanding of nutrient metabolism in bamboo stands.

The metabolism of nonstructural carbohydrates, lipids, and energy in two Cycas species with differential tolerance to unexpected freezing stress.

With the climate warming, the occurrence of freezing events is projected to increase in late spring and early autumn in the Northern Hemisphere. Observation of morphological traits showed that Cycas panzhihuaensis was more tolerant to unexpected freezing stress than C. bifida. Energy balance is crucial for plant tolerance to stress. Here, we aimed to determine whether the different responses of the two species to the unpredicted freezing stress were associated with the metabolism of energy and related substances. The effects of unexpected freezing temperatures on C. panzhihuaensis and C. bifida were studied by measuring chlorophyll fluorescence parameters, energy charge and the profile of nonstructural carbohydrates (NSC) and lipids. C. panzhihuaensis exhibited higher stability of photosynthetic machinery than C. bifida under unpredicted freezing events. Significant interaction between species and treatments were observed in the energy charge, the level of NSC and its most components and the amount of most lipid categories and lipid classes. The decrease of soluble sugar and the increase of neutral glycerolipids at the early freezing stage, the accumulation of membrane glycerolipids at the late freezing stage and the continuous decrease of energy charge during the freezing period were the characteristics of C. panzhihuaensis responding to unexpected freezing stress. The degradation of membrane glycerolipids and the continuous decrease of soluble sugar during the freezing period and the accumulation of neutral glycerolipids and energy charge at the late freezing stage represented the characteristics of C. bifida responses. The different freezing sensitivity between C. panzhihuaensis and C. bifida might be associated with the differential patterns of the metabolism of energy, NSC and lipids. C. panzhihuaensis possesses the potential to be introduced to the areas of higher latitudes and altitudes.

Physiological and Biochemical Traits of Needles Imply That Understory Light Conditions in the Growing Season May Be Favorable to Pinus koraiensis Trees

Light is often considered the primary factor leading to the regeneration failure of Korean pines (Pinus koraiensis) under the forest canopy. However, studies on the effect of light on Korean pines mainly focus on the use of an artificial sunshade net to control shade; field studies on the canopy are extremely scarce, and the current experimental results are contradictory. For a deeper understanding of the relationship between light conditions and understory Korean pine trees, the conditions of low, middle, high and full light (control) under the forest were tested at 18 years of age. The photosynthetic pigments, chlorophyll fluorescence, non-structural carbohydrate metabolism, antioxidant enzyme activity, and nutrient concentrations of current-year needles from Korean pine trees were measured. From June to September, light intensity and quality decreased under full light, but following leaf fall, understory light conditions improved slightly. As the light conditions improved, the photosynthetic pigments in the needles decreased, but Car/Chl were highest in the needles under full light. All light conditions had a positive correlation with glucose concentrations and Rubisco activity. Full-light needles had the highest APX activity, DPPH scavenging capacity, and proline concentration, as well as higher NPQ and lower Fv/Fm readings. This indicated that full-light Korean pine trees were stressed and inhibited photosynthesis to some extent, while the understory light environment may alleviate stress. The conservative strategy of storing more starch and using less glucose in understory Korean pine trees may be one of the reasons for the observed differences in growth rates among Korean pine trees under varying light conditions. Overall, this study implies that understory light during the growing season is not always unfavorable to 18-year-old Korean pine trees; this means that 18-year-old Korean pine trees still have shade tolerance to some extent and are capable of living under a canopy of deciduous trees.

Intrinsic morphology and spatial distribution of non-structural carbohydrates contribute to drought resistance of two mulberry cultivars.

Drought is one of the most adverse environmental stresses limiting plant growth and productivity. However, the underlying mechanisms regarding non-structural carbohydrates (NSCs) metabolism in source and sink organs are still not fully elucidated in woody trees. Saplings of mulberry cultivars Zhongshen1 and Wubu were subjected to a 15-day progressive drought stress. NSCs levels and gene expressions involved in NSCs metabolism were investigated in roots and leaves. The growth performance and photosynthesis, leaf stomatal morphology, and other physiological parameters were also analyzed. Under well-watered conditions, Wubu had higher root-to-shoot ratio (R/S) with higher NSCs in leaves than roots, while Zhongshen1 exhibited lower R/S with higher NSCs in roots than leaves. Under drought stress, Zhongshen1 showed decreased productivity and increased concentrations of proline, abscisic acid, reactive oxygen species and activities of antioxidant enzymes, while Wubu sustained comparable productivity and photosynthesis. Interestingly, drought resulted in decreased levels of starch and slightly increased soluble sugars in leaves of Wubu, accompanied by notable downregulation of starch-synthesizing genes and upregulation of starch-degrading genes. The similar patterns in NSCs levels and relevant gene expressions were also observed in roots of Zhongshen1. Concurrently decreased soluble sugars and unchanged starch in roots of Wubu and leaves of Zhongshen1 were found. However, the gene expressions of starch metabolism in roots of Wubu were unaltered, but in leaves of Zhongshen1 the starch metabolism was largely activated. These findings revealed that intrinsic R/S and the spatial distribution of NSCs in roots and leaves concomitantly contributed to drought resistance in mulberry.

Exogenous Melatonin Reprograms the Rhizosphere Microbial Community to Modulate the Responses of Barley to Drought Stress.

The rhizospheric melatonin application-induced drought tolerance has been illuminated in various plant species, while the roles of the rhizosphere microbial community in this process are still unclear. Here, the diversity and functions of the rhizosphere microbial community and related physiological parameters were tested in barley under the rhizospheric melatonin application and drought. Exogenous melatonin improved plant performance under drought via increasing the activities of non-structural carbohydrate metabolism enzymes and activating the antioxidant enzyme systems in barley roots under drought. The 16S/ITS rRNA gene sequencing revealed that drought and melatonin altered the compositions of the microbiome. Exogenous melatonin increased the relative abundance of the bacterial community in carbohydrate and carboxylate degradation, while decreasing the relative abundance in the pathways of fatty acid and lipid degradation and inorganic nutrient metabolism under drought. These results suggest that the effects of melatonin on rhizosphere microbes and nutrient condition need to be considered in its application for crop drought-resistant cultivation.

Differential Growth Responses of Alternanthera philoxeroides as Affected by Submergence Depths.

Global climate change has resulted in an increase in intensity and frequency of flooding, plants living in lowlands, and shore areas have to confront submergence caused by flooding, submergence-tolerant plants usually respond by adopting either escape or quiescence strategies. While certain plants exhibit a changeover from escape strategy upon partial submergence to quiescence strategy under complete shallow submergence, it remains unknown whether plants completely submerged at different water depths would adjust their strategies to cope with the change in submergence depth. Alternanthera philoxeroides is an ideal species to explore this adjustment as it is widely distributed in flood-disturbed habitats and exhibits an escape strategy when completely submerged in shallow waters. We investigated the responses of A. philoxeroides in terms of morphology, anatomy, and non-structural carbohydrate metabolism by conducting experiments using a series of submergence depths (0, 2, 5, and 9 m). During the submergence treatment, environmental factors such as light, dissolved oxygen, and temperature for submerged plants were kept constant. The results showed that A. philoxeroides plants submerged at depth of 2 m presented an escape strategy via fast stem elongation, extensive pith cavity development, and small biomass loss. However, the retarded stem elongation, reduced pith cavity transverse area, and increased biomass loss along the water depth gradient indicated that A. philoxeroides altered its growth response as water depth increased from 2 to 9 m. It is found that the changeover of response strategies occurred at higher submergence depths (5–9 m). Based on the results of our experiments, we demonstrated that water depth played an important role in driving the change in strategy. The water-depth-dependent growth performance of A. philoxeroides would benefit the species in habit exploration and exploitation. Further studies should focus on the performances of plants when submerged at varied water depths with different light climates and dissolved oxygen content, and how water depths drive the response behaviors of the submerged plants.

Dynamics of non-structural carbohydrates in Pinus pallasiana D. Don needles under different forest growth conditions of ravine anti-erosion plantations

Abstract The research was aimed at analysing the peculiarities of non-structural carbohydrate metabolism in the needles of Pinus pallasiana D. Don in anti-erosion plantations on the slope and in the thalweg of the Viyskovyi ravine under different forest growth conditions. The ravine is located in the Dnipropetrovsk region and belongs to the southern geographical variant of ravine forests. The studied plants grew at three experimental sites of man-made plantation: in the thalweg (forest growth conditions – mesophilic, fresh, CL2), in the middle part of the slope of the southern exposure (mesoxerophilic, somewhat dry, or semi-arid, CL1) and on the upper part of this slope (xerophilic, arid, CL0–1). Changes in glucose, fructose, reducing sugars, sucrose and starch during the period from May to October were studied. The concentration of osmotically active substances (glucose, sucrose) increases in the months with the most unfavourable hydrothermal parameters, especially in plants of mesoxerophilic and xerophilic forest growth conditions. The dynamics of fructose content revealed two maxima (July and October), when the concentration of glucose tends to increase steadily, with the highest values found in October. During the study period, the level of fructose in the needles under the arid conditions of the upper and middle parts of the slope was much lower than under the fresh conditions of the thalweg. The dynamics curve of the starch content tends to decrease from the maximum values in May to the first minimum in August. It is followed by some increase in the concentration of this polysaccharide that does not reach the previous values. The second minimum is registered in October. Such changes in the level of starch in the needles of plants are observed under all forest growth conditions. The decrease in polysaccharide content is consistent with the increase in glucose and sucrose, especially in August. A more significant increase in the concentration of soluble osmoprotective sugars (glucose, sucrose) in P. pallasiana needles under unfavourable hydrothermal conditions compared to normal moisture conditions indicates the ability of plants to adapt to mesoxerophilic and xerophilic conditions.

Influence of soil moisture level on metabolism of non-structural carbohydrates in Quercus robur leaves

The long-term increases in average temperature and intensification of droughts which characterise the current state of the Earth’s climate system have a negative impact on forest ecosystems and can lead to a decrease in their area and deterioration of the living conditions of their components. In the conditions of the Ukrainian Steppe an important environmental, antierosion, water-protective and soil-protective role belongs to the ravine forests. The most valuable component of the ravine forests is presented by natural populations of common oak (Quercus robur L.), which are able to tolerate the arid climate typical of the steppe region. But with global warming, the endurance of this species is changing. It is believed that a significant role in plant adaptation to drought and high temperatures may belong to non-structural carbohydrates. Therefore, it is important to study changes in the concentration of these substances in the leaves of this leading species under the action of adverse hydrothermal conditions. The article analyzes the content and dynamics of soluble sugars (glucose, fructose, sucrose) and starch in the leaves of Quercus robur L. under different forest growth conditions of the ravine forest (hygromesophilic (CL2–3), mesoxerophilic (CL1) and xerophilic (CL0)). The research was conducted in the forest in the Viyskove area (steppe zone of Ukraine) in the thalweg and at different levels of slope of southern exposure. Content of glucose, fructose, sugar and starch in Quercus robur leaves was determined. It was found that when exposed to high temperatures and increasing water stress during the vegetation period in xerophilic (CL0–1) and mesoxerophilic (CL1) forest growth conditions, the concentration of both glucose and sucrose in the leaves of Q. robur increases and it becomes much higher than in conditions of more optimal water supply. At the same time, the disaccharide content increases more significantly than that of monosaccharide. The greatest amount of these sugars is observed in the driest months (July, August), when conditions for providing plants with water are the most stressful. When water stress grows the increase in concentration of glucose and sucrose is correlated with reduction of starch content. It has been found that the concentration of fructose in Q. robur leaves in droughty conditions of growing was comparable to more favourable conditions of moisture. In September, there is a decline in the content of all forms of non-structural carbohydrates in the leaves of plants of all variants compared to the previous month, especially in conditions of adverse water supply. Therefore, forest growth conditions do not affect the nature of the dynamics of soluble sugars and starch in the leaves of Q. robur, although they change their quantitative indicators. Based on the protective function of sugars under the action of stressors on plants, we can assume that in conditions of significant lack of moisture in the soil their accumulation in the leaves in areas with mesoxerophilic and xerophilic hygrotopes plays an important role in increasing Q. robur drought resistance.

Non-structural Carbohydrate Metabolism in the Flesh of Stone Fruits of the Genus Prunus (Rosaceae) - A Review.

Non-structural carbohydrates are abundant constituents of the ripe flesh of all stone fruits. The bulk of their content comprises sucrose, glucose, fructose and sorbitol. However, the abundance of each of these carbohydrates in the flesh differs between species, and also with its stage of development. In this article the import, subcellular compartmentation, contents, metabolism and functions of non-structural carbohydrates in the flesh of commercially cultivated stone fruits of the family Rosaceae are reviewed.

Effects of CO2 enrichment on non-structural carbohydrate metabolism in leaves of cucumber seedlings under salt stress

The effects of CO2 enrichment (800 ± 40 μmol·mol−1) on sucrose metabolism, the glycolytic (EMP) pathway, and tricarboxylic acid (TCA) cycle intermediates and their key enzyme activities in leaves of cucumber (Cucumis sativus L. cv. ‘Jinyou No. 35′) seedlings under salt stress (80 mmol·L−1 NaCl) in solution cultures were investigated. After 7 d of the experimental treatments, salt stress significantly reduced hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) activities, causing decreases in the pyruvate, citrate, nicotinamide adenine dinucleotide (NADH), adenosine triphosphate(ATP) and adenosine diphosphate(ADP) contents in leaves. Enriched [CO2] regulated the invertase (soluble acid and neutral invertase) activity levels in leaves under salt stress. This facilitated the normal metabolism of sucrose, providing more substrates (fructose and starch) for respiratory metabolism, effectively participating in the glycolytic pathway and tricarboxylic acid cycle, and providing more energy to prevent salt-induced injury. Therefore, the negative effects of salt stress were alleviated under enriched [CO2] conditions and resistance was enhanced.

Survival of completely submerged Salix triandroides cuttings is associated with non-structural carbohydrate metabolism

The growth, survival, and non-structural carbohydrate metabolism in Salix triandroides cuttings, cultivated under no flooding, incomplete submergence, or complete submergence conditions (0, 25, and 50 cm of water above the soil surface, respectively), were measured after 50, 80, 110, and 140 days. Both submergence conditions decreased the biomass of the leaf, stem, and root, plant height, root length, and root number. As the duration of the treatments increased, these growth parameters gradually increased for the control and incompletely submerged conditions, but remained relatively constant for the completely submerged condition. The survival ratio was 100% across the experimental period for plants under the control and incompletely submerged conditions; however for plants under the completely submerged condition, it was 100% after 50 and 80 days but decreased to 91.7 and 33.3% after 110 and 140 days, respectively. Compared with the plants under control and incomplete submergence conditions, the completely submerged plants had significantly lower concentrations of soluble sugars and starch. As the concentration of soluble sugars in the completely submerged plants fell to 19.2%, and that of starch to 23.5% of that in the control plants, their survival ratio decreased to 33.3%. The results indicated that the survival of the S. triandroides cuttings grown in complete submergence conditions was associated with non-structural carbohydrate metabolism.

干旱胁迫下紫花苜蓿幼苗非结构性碳水化合物代谢对NO的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱胁迫下紫花苜蓿幼苗非结构性碳水化合物代谢对NO的响应 DOI: 10.5846/stxb201807231573 作者: 作者单位: 甘肃农业大学,甘肃农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31560663） Responses of non-structural carbohydrate metabolism of Medicago sativa seedlings to nitric oxide under drought stress Author: Affiliation: Gansu Agricultural University,Gansu Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以紫花苜蓿（Medicago sativa）为材料，采用盆栽试验方法，用聚乙二醇（PEG-6000）作为渗透介质模拟干旱胁迫，外源喷施NO供体硝普钠，NO清除剂（carboxy-PTIO，cPTIO），对紫花苜蓿幼苗叶片、根系中非结构性碳水化合物含量及相关酶活性的变化进行研究，探讨NO对紫花苜蓿耐旱机制的作用。结果表明：外源NO促进了紫花苜蓿叶片中淀粉的分解、根系中淀粉的积累，提高叶片及根系中可溶性糖（蔗糖、果糖和葡萄糖）含量，降低了渗透势，促进细胞吸水，缓解干旱造成的损伤。此外，外源NO能提高干旱胁迫下紫花苜蓿叶片中蔗糖合成酶（SS）、酸性转化酶（AI）和中性转化酶（NI）活性，降低了蔗糖磷酸合成酶（SPS）的活性，提高根系中SS、SPS和转化酶活性，使蔗糖的合成与分解处于高水平的动态平衡，增强了紫花苜蓿的抗旱性。而NO清除剂cPTIO则会不同程度的抑制紫花苜蓿幼苗中非结构性碳水化合物（NSC）及其相关酶活性。因此，NO可以通过调控NSC的代谢响应干旱胁迫，缓解干旱胁迫造成的不利影响，在紫花苜蓿的抗旱中扮演着重要的角色。 Abstract:The effects of nitric oxide on non-structural carbohydrate metabolism of Medicago sativa seedlings leaves and roots under drought stress by 10% PEG were investigated. Solutions with:(i) osmotic potentials obtained using polyethylene-glycol-6000 (PEG-6000); (ii) a nitric oxide donor sodium nirorpusside (SNP); (iii) an NO scavenger (carboxy-PTIO, cPTIO); were sprayed onto the leaves of alfalfa seedlings in pot experiment at different combinations. The results showed that exogenous nitric oxide promoted the starch decomposition of leaves, the accumulation of starch in roots and increased the content of soluble sugar (sucrose, fructose and glucose) in leaves and roots in Medicago sativa seedlings under drought stress, which decreased the osmotic potential, promoted cell water absorption and alleviated damage caused by drought. Furthermore, under drought stress exogenous nitric oxide can increase the activity of sucrose synthetase (SS), acid invertase (AI), neatral invertase (NI), reduce the activity of Sucrose phosphate synthase(SPS) in leaves and can increase the activity of SS, SPS, invertase in roots, so that make the synthesis and decomposition of sucrose at a high level of dynamic balance. It enhances the drought resistance of alfalfa. The metabolism of NSC and related enzymes were inhibited by NO scavenger cPTIO. Therefore, nitric oxide played an important role in the drought resistance of Medicago sativa. It can regulate the metabolic of NSC response to drought stress and alleviate the adverse effects caused by drought stress. 参考文献 相似文献 引证文献

Non-Structural Carbohydrate Metabolism, Growth, and Productivity of Maize by Increasing Plant Density

Increasing plant density seems to improve the productivity of maize crops, and the understanding of how the metabolism of non-structural carbohydrates is affected in plants under high crop density is critical. Thus, with the objective of further clarifying this issue, maize plants were subjected to densities from 30,000 to 90,000 plants ha−1, and the plant growth, soluble sugars and starch contents, invertase and sucrose synthase activities, and plant production were evaluated. We found that the stalk is more sensitive to the increasing plant density than leaves and kernels. The dry weight of the stalk and leaves per single plant decreased more drastically from low to intermediate plant densities, while grain production was reduced linearly in all plant density ranges, leading to higher values of harvest index in intermediate plant densities. The sucrose concentration did not change in leaves, stalk, or kernels of plants subjected to increasing plant densities at the R4 stage. Also, the specific activity of soluble invertase, bound invertase, and sucrose synthase did not change in leaf, stalk, or kernels of plants subjected to increased plant density. The productivity was increased with the increase in plant density, using narrow row (0.45 m) spacing.

Non-structural carbohydrate metabolism and postharvest conservation of gerbera flowers

The species Gerbera jamesonii Adlam has great economic importance in the ornamental sector, due to exuberance of floral stems. However, florists face some challenges such as postharvest handling and difficulty of conservation. Therefore, this study aimed to characterize the non-structural carbohydrate content in different floral stages of G. jamesonii var. Dawn and evaluate the effect of preservative solutions during the postharvest storage of this species. For this purpose, it was quantified TSS, RS and NRS from the seven stages of gerbera stems ontogeny (E1, E2, E3, E4, E5, E6 and E7). The preservative solutions used were: T1) distilled water; T2) citric acid (100 mg L-1); T3) glucose (20 g L-1); T4) gibberellic acid (GA3 , 5 mg L-1); T5) calcium chloride (CaCl2 , 20g L-1) and T6) Sodium Thiosulphate (STS, 20 mM). The effect of preservative solutions were assessed daily, considering the longevity of flowers, variation in the absorption of preservative solution, pH of the solution and fresh mass variation. The experimental design was completely randomized with four replicates. There was a difference in carbohydrate metabolism during floral opening and senescence. In the orange bracts there was a lower TSS content, while in the inflorescences it was observed a reduction in the yellowish, greenish-green and greenish stages. The content of RS increased in the bracts, whereas in the inflorescence there was no difference. The NRS content was higher in the orange bracts, showing lower rates in the inflorescences in yellowish and yellowish greenish stages. The preservative solutions had an impact, on the floral stem longevity, varying according to the solutions used, i.e. CaCl2 and STS reduced the durability of gerbera flower in 9.25 and 11.5 days, respectively, compared to stems kept in distilled water. The glucose solution did not promote a significant difference compared to water. Therefore, we conclude that there is variation in the metabolism of non-structural carbohydrates during the floral development of G. jamesonii var. Dawn and the tested solutions were not effective in promoting postharvest conservation of gerbera.

The influence of short-term cold stress on the metabolism of non-structural carbohydrates in polar grasses

AbstractPlants adapt to extremely low temperatures in polar regions by maximizing their photosynthetic efficiency and accumulating cryoprotective and osmoprotective compounds. Flowering plants of the family Poaceae growing in the Arctic and in the Antarctic were investigated. Their responses to cold stress were analyzed under laboratory conditions. Samples were collected after 24 h and 48 h of cold treatment. Quantitative and qualitative changes of sugars are found among different species, but they can differ within a genus of the family Poaceae. The values of the investigated parameters in Poa annua differed considerably depending to the biogeographic origin of plants. At the beginning of the experiment, Antarctic plants were acclimatized in greenhouse characterized by significantly higher content of sugars, including storage reserves, sucrose and starch, but lower total protein content. After 24 h of exposure to cold stress, much smaller changes in the examined parameters were noted in Antarctic plants than in locally grown specimens. Total sugar content and sucrose, starch and glucose levels were nearly constant in P. annua, but they varied significantly. Those changes are responsible for the high adaptability of P. annua to survive and develop in highly unsupportive environments and colonize new regions.

Impact of ethylene and 1-MCP on sprouting and sugar accumulation in stored potatoes

Long term storage of potato tubers allows year round availability of the crop but is limited by sprouting. Continuous exposure to ethylene during storage prolongs storage life of potatoes by suppressing sprouting, yet there is a lack of information on whether continuous ethylene treatment is required throughout storage. Potato cvs. Saturna and Russet Burbank were stored at 6°C under four ethylene treatments (viz. continuous ethylene (10μLL−1), continuous air, transfer from air to ethylene after first indication of sprouting and vice versa) for thirty weeks in 2008–2009 (Year 1). In Year 2 (2009–2010), tubers were stored under the same treatments and duration as in Year 1, with the addition of 1-MCP (1μLL−1) applied for 24h at harvest or at first indication of peeping. Samples were taken after harvest and at specific intervals during storage. Respiration rate measured at each sampling point. Fructose, glucose and sucrose were determined in potato flesh of all cultivars as ethylene has been reported to have some negative effects on non-structural carbohydrate metabolism. Sprouting was also measured at the end of the experiment. Ethylene applied after first indication of sprouting was as effective at suppressing sprouting for cv. Russet Burbank as when applied continuously; the implications of which are that the cost of ethylene application in store rooms could be reduced by manipulating timing of continuous application. In addition, application of ethylene after the first indication of sprouting had little to no effect on tuber sugar accumulation compared with continuous ethylene application from harvest.

Characterization of multiple SPS knockout mutants reveals redundant functions of the four Arabidopsis sucrose phosphate synthase isoforms in plant viability, and strongly indicates that enhanced respiration and accelerated starch turnover can alleviate the blockage of sucrose biosynthesis

We characterized multiple knock-out mutants of the four Arabidopsis sucrose phosphate synthase (SPSA1, SPSA2, SPSB and SPSC) isoforms. Despite their reduced SPS activity, spsa1/spsa2, spsa1/spsb, spsa2/spsb, spsa2/spsc, spsb/spsc, spsa1/spsa2/spsb and spsa2/spsb/spsc mutants displayed wild type (WT) vegetative and reproductive morphology, and showed WT photosynthetic capacity and respiration. In contrast, growth of rosettes, flowers and siliques of the spsa1/spsc and spsa1/spsa2/spsc mutants was reduced compared with WT plants. Furthermore, these plants displayed a high dark respiration phenotype. spsa1/spsb/spsc and spsa1/spsa2/spsb/spsc seeds poorly germinated and produced aberrant and sterile plants. Leaves of all viable sps mutants, except spsa1/spsc and spsa1/spsa2/spsc, accumulated WT levels of nonstructural carbohydrates. spsa1/spsc leaves possessed high levels of metabolic intermediates and activities of enzymes of the glycolytic and tricarboxylic acid cycle pathways, and accumulated high levels of metabolic intermediates of the nocturnal starch-to-sucrose conversion process, even under continuous light conditions. Results presented in this work show that SPS is essential for plant viability, reveal redundant functions of the four SPS isoforms in processes that are important for plant growth and nonstructural carbohydrate metabolism, and strongly indicate that accelerated starch turnover and enhanced respiration can alleviate the blockage of sucrose biosynthesis in spsa1/spsc leaves.

Effects of short- and long-term elevated CO2 on the expression of ribulose-1,5-bisphosphate carboxylase/oxygenase genes and carbohydrate accumulation in leaves of Arabidopsis thaliana (L.) Heynh.

To investigate the proposed molecular characteristics of sugar-mediated repression of photosynthetic genes during plant acclimation to elevated CO2, we examined the relationship between the accumulation and metabolism of nonstructural carbohydrates and changes in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) gene expression in leaves of Arabidopsis thaliana exposed to elevated CO2. Long-term growth of Arabidopsis at high CO2 (1000 microL L-1) resulted in a 2-fold increase in nonstructural carbohydrates, a large decrease in the expression of Rubisco protein and in the transcript of rbcL, the gene encoding the large subunit of Rubisco (approximately 35-40%), and an even greater decline in mRNA of rbcS, the gene encoding the small subunit (approximately 60%). This differential response of protein and mRNAs suggests that transcriptional/posttranscriptional processes and protein turnover may determine the final amount of leaf Rubisco protein at high CO2. Analysis of mRNA levels of individual rbcS genes indicated that reduction in total rbcS transcripts was caused by decreased expression of all four rbcS genes. Short-term transfer of Arabidopsis plants grown at ambient CO2 to high CO2 resulted in a decrease in total rbcS mRNA by d 6, whereas Rubisco content and rbcL mRNA decreased by d 9. Transfer to high CO2 reduced the maximum expression level of the primary rbcS genes (1A and, particularly, 3B) by limiting their normal pattern of accumulation through the night period. The decreased nighttime levels of rbcS mRNA were associated with a nocturnal increase in leaf hexoses. We suggest that prolonged nighttime hexose metabolism resulting from exposure to elevated CO2 affects rbcS transcript accumulation and, ultimately, the level of Rubisco protein.

Changes in soluble carbohydrates and enzymic activities in maturing soybean seed tissues

Enzyme activities were compared with the accumulation of soluble carbohydrates in seed coats, cotyledons and embryonic axes of field-grown soybean ( Glycine max L. Merr. cv. Williams 82) seeds during seed maturation to examine the function of each seed tissue in non-structural carbohydrate metabolism. The vascularized seed coat was comparatively high in monosaccharides (glucose and fructose) which corresponded to greater acid invertase activity per gram dry weight than cotyledons and axes. The embryo (cotyledon+embryonic axis) was high in oligosaccharide content, and contained greater mean activity levels of sucrose synthase, alkaline invertase, galactinol synthase and α-galactosidase than the seed coat. There was little difference in the sucrose-phosphate synthase activity among these three tissues. The accumulation of raffinose saccharides (raffinose and stachyose) increased rapidly in the embryo during seed maturation. Activities of alkaline invertase, sucrose synthase, galactinol synthase, α-galactosidase, fructose-1,6-bisphosphate aldolase, malate dehydrogenase, and glucose-6-phosphate dehydrogenase were highest in embryonic axes. Initial maturation of soybean seeds may be distinguished developmentally by the yellowing of embryonic axes at 40–45 days after flowering. This change was found to coincide with increases in sucrose synthase and galactinol synthase activities, and with the initiation of a rapid accumulation of raffinose saccharides in the embryonic axis.