Non-structural Carbohydrate Levels Research Articles

NAA and STS effects on bract survival time, carbohydrate content, respiration rate and carbohydrate balance of potted Bougainvillea spectabilis Willd.

The aims of this work were to increase knowledge on the physiology of bract abscission in Bougainvillea spectabilis ‘Killie Campbell’ plants with regard to respiration and carbon balance. Using the effects induced by silver shiosulphate (STS) and/or naphthalene acetic acid (NAA, at high concentration: 500 mg L −1) on bract abscission under interior conditions the relationship between bract survival time (longevity) and respiration rate or carbohydrate levels was investigated. Treatments that included NAA significantly reduced bract abscission. Unexpectedly, the higher the levels of bract soluble and total carbohydrates, measured at day 10 postproduction (PP), the higher the abscission of bracts. These results show, for the first time, that abscission can be positively correlated with non-structural carbohydrate levels in the organ that abscises. Bract respiration rate was significantly affected by treatment and PP day. Treatments that had higher bract respiration rates (WATER and STS) also had higher levels of non-structural carbohydrates in the bracts. Bract respiration rate decreased from day 10 to day 17 PP by approximately 50% (average of all treatments) and was negatively correlated with bract survival time. In the carbon balance per gram of bract dry weight, the treatments WATER and STS, showed the largest decrease in the content of total carbohydrates and had the highest consumption of carbohydrates through respiration. These were the bracts therefore that needed to import a higher amount of carbohydrates per gram of bract dry weight. In the carbon balance for the total mass of bracts and adjacent stems in an average plant, the treatments WATER and STS showed the largest decreases in total carbohydrate during postproduction. However, contrary to the results per gram of bract dry weight, the highest total consumption of carbohydrates by respiration was obtained for the NAA and STS + NAA treatments. Thus bracts that last longer have lower individual carbon consumption while, at the plant level, the increased number of remaining bracts causes a higher overall expenditure. Respiration rate has been used as an indicator of flower longevity and this correlation is here extended for the flower + bract system. Plants that had higher bract respiration rates, most probably, had a higher flow of carbohydrates through the bracts (and flowers), which, in the end, was sensed as a higher carbohydrate level.

Photosynthesis and assimilate partitioning between carbohydrates and isoprenoid products in vegetatively active and dormant guayule: physiological and environmental constraints on rubber accumulation in a semiarid shrub

The stems and roots of the semiarid shrub guayule, Parthenium argentatum, contain a significant amount of natural rubber. Rubber accumulates in guayule when plants are vegetatively and reproductively dormant, complicating the relationship between growth/reproduction and product synthesis. To evaluate the factors regulating the partitioning of carbon to rubber, carbon assimilation and partitioning were measured in guayule plants that were grown under simulated summer- and winter-like conditions and under winter-like conditions with CO(2) enrichment. These conditions were used to induce vegetatively active and dormant states and to increase the source strength of vegetatively dormant plants, respectively. Rates of CO(2) assimilation, measured under growth temperatures and CO(2) , were similar for plants grown under summer- and winter-like conditions, but were higher with elevated CO(2) . After 5 months, plants grown under summer-like conditions had the greatest aboveground biomass, but the lowest levels of non-structural carbohydrates and rubber. In contrast, the amount of resin in the stems was similar under all growth conditions. Emission of biogenic volatile compounds was more than three-fold higher in plants grown under summer- compared with winter-like conditions. Taken together, the results show that guayule plants maintain a high rate of photosynthesis and accumulate non-structural carbohydrates and rubber in the vegetatively dormant state, but emit volatile compounds at a lower rate when compared with more vegetatively active plants. Enrichment with CO(2) in the vegetatively dormant state increased carbohydrate content but not the amount of rubber, suggesting that partitioning of assimilate to rubber is limited by sink strength in guayule.

Temporal heterogeneity of cold acclimation phenotypes in Arabidopsis leaves

To predict the effects of temperature changes on plant growth and performance, it is crucial to understand the impact of thermal history on leaf morphology, anatomy and physiology. Here, we document a comprehensive range of leaf phenotypes in 25/20 degrees C-grown Arabidopsis thaliana plants that were shifted to 5 degrees C for up to 2 months. When warm-grown, pre-existing (PE) leaves were exposed to cold, leaf thickness increased due to an increase in mesophyll cell size. Leaves that were entirely cold-developed (CD) were twice as thick (eight cell layers) as their warm-developed (WD) counterparts (six layers), and also had higher epidermal and stomatal cell densities. After 4 d of cold, PE leaves accumulated high levels of total non-structural carbohydrates (TNC). However, glucose and starch levels declined thereafter, and after 45 d in the cold, PE leaves exhibited similar TNC to CD leaves. A similar phenomenon was observed in delta(13)C and a range of photosynthetic parameters. In cold-treated PE leaves, an increase in respiration (R(dark)) with cold exposure time was evident when measured at 25 degrees C but not 5 degrees C. Cold acclimation was associated with a large increase in the ratio of leaf R(dark) to photosynthesis. The data highlight the importance of understanding developmental thermal history in determining individual phenotypic traits.

Effects of Soil Temperature on Growth and Root Function in Rice

The objective of this study was to clarify the effects of soil temperature in the stage from late tillering to panicle initiation (SI) and during the grain-filling stage (SII) on grain setting, dry matter production, photosynthesis, non-structural carbohydrate (NSC), xylem exudation and abscisic acid (ABA) levels in rice (Oryza sativa L. cv. Koshihikari). Rice plants were exposed to four different soil temperatures during SI or SII: 17.5, 25, 31.5 and 36.5°C (ST18, ST25, ST32 and ST37, respectively). The yield, yield components, grain filling and quality in SI were negatively influenced by high soil temperature of 37°C. On the other hand, there was no significant difference in those characters among temperature treatments in SII. The root/shoot ratio was smallest in the ST37 plants in both SI and SII, mainly due to their lighter root weight. At 7 days after initiation of treatment (DAT) in both SI and SII, the photosynthetic and xylem exudation rate tended to increase slightly as soil temperature increased up to 32°C. At 21 DAT, however, the photosynthetic rate was lowest in ST37, with concurrent decrease of diffusion conductance and SPAD value. In addition, decrease of NSC concentration in stem and xylem exudation rate, and increase of ABA level in leaves and xylem exudate were observed in ST37 plants at 21 DAT. These results suggested that high soil temperature before heading especially influenced yield, grain quality and plant growth. Possible mechanisms of the effect of soil temperature are discussed.

Drought tolerance of two black poplar (Populus nigra L.) clones: contribution of carbohydrates and oxidative stress defence

Drought is expected to become an increasingly important factor limiting tree growth caused by climate change. Two divergent clones of Populus nigra (58-861 and Poli) originating from contrasting environments were subjected to water limitation (WL) to elucidate whether they differ in tolerance to drought, which mechanisms to avoid stress they exhibit and whether drought has an impact on the interactions between roots and shoots. Limiting water availability caused photosynthetic rate and total non-structural carbohydrate (TNC) levels to decrease in 58-861. However, starch-degrading enzyme activity and gene expression were induced in roots, and soluble sugar levels were higher than in well-watered (WW) plants. These data suggest that assimilation and partitioning of carbon to the roots are decreased, resulting in mobilization of stored starch. In contrast, the photosynthetic rate of Poli was reduced only late in the treatment, and carbohydrate levels in WL plants were higher than in WW plants. Superoxide dismutase (SOD) activity and gene expression were higher in Poli than in 58-861, even in WW plants, leading to a higher capacity to defend against oxidative stress.

Nitrogen and carbon source–sink relationships in trees at the Himalayan treelines compared with lower elevations

No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source-sink ratio of carbon; or (3) a sufficient C-N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non-structural carbohydrates (NSC) in trees were species-specific and site-dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source-sink relationship.

Growth, photosynthesis, nitrogen partitioning and responses to CO2 enrichment in a barley mutant lacking NADH‐dependent nitrate reductase activity

Plant growth, photosynthesis and leaf constituents were examined in the wild-type (WT) and mutant nar1 of barley (Hordeum vulgare L. cv. Steptoe) that contains a defective structural gene encoding NADH-dependent nitrate reductase (NADH-NAR). In controlled environment experiments, total biomass, rates of photosynthesis, stomatal conductance, intercellular CO(2) concentrations and foliar non-structural carbohydrate levels were unchanged or differed slightly in the mutant compared with the WT. Both genotypes displayed accelerated plant growth rates when the CO(2) partial pressure was increased from 36 to 98 Pa. Total NADH-NAR activity was 90% lower in the mutant than in the WT, and this was further decreased by CO(2) enrichment in both genotypes. Inorganic nitrate was greater in the mutant than in the WT, whereas in situ nitrate assimilation by excised leaves was two-fold greater for the WT than for the mutant. Foliar ammonia was 50% lower in the mutant than in the WT under ambient CO(2). Ammonia levels in the WT were decreased by about one-half by CO(2) enrichment, whereas ammonia was unaffected by elevated CO(2) in mutant leaves. Total soluble amino acid concentrations in WT and mutant plants grown in the ambient CO(2) treatment were 30.1 and 28.4 micromol g(-1) FW, respectively, when measured at the onset of the light period. Seven of the twelve individual amino acids reported here increased during the first 12 h of light in the ambient CO(2) treatment, leading to a doubling of total soluble amino acids in the WT. The most striking effect of the mutation was to eliminate increases of glutamine, aspartate and alanine during the latter half of the photoperiod in the ambient CO(2) treatment. Growth in elevated CO(2) decreased levels of total soluble amino acids on a diurnal basis in the WT but not in mutant barley leaves. The above results indicated that a defect in NADH-NAR primarily affected nitrogenous leaf constituents in barley. Also, we did not observe synergistic effects of CO(2) enrichment and decreased foliar NADH-NAR activity on most N-containing compounds.

Growth at elevated CO 2 delays the adverse effects of drought stress on leaf photosynthesis of the C 4 sugarcane

Sugarcane (Saccharum officinarum L. cv. CP72-2086) was grown in sunlit greenhouses at daytime [CO(2)] of 360 (ambient) and 720 (elevated)mumolmol(-1). Drought stress was imposed for 13d when plants were 4 months old, and various photosynthetic parameters and levels of nonstructural carbohydrates were determined for uppermost fully expanded leaves of well-watered (control) and drought stress plants. Control plants at elevated [CO(2)] were 34% and 25% lower in leaf stomatal conductance (g(s)) and transpiration rate (E) and 35% greater in leaf water-use efficiency (WUE) than their counterparts at ambient [CO(2)]. Leaf CO(2) exchange rate (CER) and activities of Rubisco, NADP-malate dehydrogenase, NADP-malic enzyme and pyruvate P(i) dikinase were marginally affected by elevated [CO(2)], but were reduced by drought, whereas activity of PEP carboxylase was reduced by elevated [CO(2)], but not by drought. At severe drought developed at day 12, leaf g(s) and WUE of ambient-[CO(2)] stress plants declined to 5% and 7%, while elevated-[CO(2)] stress plants still maintained g(s) and WUE at 20% and 74% of their controls. In control plants, elevated [CO(2)] did not enhance the midday levels of starch, sucrose, or reducing sugars. For both ambient- and elevated-[CO(2)] stress plants, severe drought did not affect the midday level of sucrose but substantially reduced that of starch. Nighttime starch decomposition in control plants was 55% for ambient [CO(2)] and 59% for elevated [CO(2)], but was negligible for stress plants of both [CO(2)] treatments. For both ambient-[CO(2)] control and stress plants, midday sucrose level at day 12 was similar to the predawn value at day 13. In contrast, sucrose levels of elevated-[CO(2)] control and stress plants at predawn of day 13 were 61-65% of the midday values of day 12. Levels of reducing sugars were much greater for both ambient- and elevated-[CO(2)] stress plants, implying an adaptation to drought stress. Sugarcane grown at elevated [CO(2)] had lower leaf g(s) and E and greater leaf WUE, which helped to delay the adverse effects of drought and, thus, allowed the stress plants to continue photosynthesis for at least an extra day during episodic drought cycles.

Effects of Trinexapac‐Ethyl Foliar Application on Creeping Bentgrass Responses to Combined Drought and Heat Stress

Simultaneous drought and heat stress is detrimental to turfgrass growth. Growth regulators may influence plant responses to stresses. The objective of this study was to determine effects of pretreatment with trinexapac‐ethyl (TE) on creeping bentgrass (Agrostis stolonifera L.) responses to subsequent exposure to combined heat and drought stress. Plants were treated with TE (1.95 mL L−1 [v/v], Primo Maxx) every 14 d for 42 d and then exposed to combined drought and heat (35°C) in growth chambers. Application of TE increased turf quality and relative water content and chlorophyll content during 21 d of stress. Trinexapac‐ethyl–treated plants had increased growth rate and maintained constant canopy photosynthetic rate (Pn) and photochemical efficiency (Fv/Fm) during the stress period, while these parameters declined for the untreated control. Trinexapac‐ethyl–treated plants maintained lower evapotranspiration rate (ET) under nonstressed control conditions, but higher ET at 21 d of stress. Trinexapac‐ethyl–treated plants showed no differences from untreated plants in osmotic adjustment, and had lower levels of total nonstructural carbohydrates during the stress period. The study suggests that TE application enhanced turf performance under stress, as demonstrated by maintenance of higher turf quality and growth rate during a prolonged period of com bined stress. The beneficial effects of TE on bentgrass stress responses could be related to the maintenance of photosynthetic activities and greater level of cellular hydration. These and other published data indicate that use of TE on creeping bentgrass that seasonally experiences heat and drought stresses could benefit its performance.

Roots of Australian alpine plant species contain high levels of stored carbohydrates independent of post-fire regeneration strategy

The relationships between root morphology, level of stored non-structural carbohydrates and post-fire regeneration strategy were investigated in 37 Australian alpine plant species: 6 reseeders, 14 resprouters and 17 capable of both reseeding and resprouting. High concentrations of stored carbohydrate (up to 61.8% DW) were a feature of most species, with more than half of the 37 species containing non-structural carbohydrate concentrations of more than 10%. Fructan was the major reserve polysaccharide in 32 of the 37 species, with particularly high concentrations in the Asteraceae (up to 43.1%). Herbaceous species stored higher concentrations of carbohydrates and had fleshier roots than did shrub species, but swollen underground storage organs were found in only one species (Microseris scapigera sensu Willis1, Asteraceae). There was no significant relationship between post-fire regeneration strategy and either root morphology or level of carbohydrate storage, contrasting with results from drier, Mediterranean environments. Root storage of high levels of carbohydrate, and especially fructan, in Australian alpine species could therefore result from an adaptation to the alpine environment, such as a need for annual regeneration of leaf tissue in alpine conditions.

Changes in carbohydrate contents of Zantedeschia leaves under gibberellin-stimulated flowering

The effect of gibberellic acid (GA3) on the carbohydrate accumulation in relation to vegetative growth of Zantedeschia ‘Black Magic’ plants undergoing transition to flowering was investigated. In response to GA treatment the carbohydrate level increased independently of earlier stimulation of shoot emergence. Under vegetative growth stage the content of reducing sugars of leaf blades was 2.5-fold higher than in control plants, and suggests the stimulation of photosynthetic activity. The changes observed during the flowering, in principle noted in petiole tissues, support the GA-effect on assimilate transport to the sink organs. Moreover, the high level of non-structural carbohydrates in petiole tissues, in particular reducing sugars, can be an effect of photosynthetic activity of these organs and/or essential for osmoregulation and high turgor pressure. The results indicate that apart from the influence on the shoot emergence, the GAs may stimulate the photosynthetic activity from the beginning of shoot growth and are thus responsible for the enhancement of callas flower yield.

Changes in resource concentration and defence during leaf development in a tough-leaved (Nothofagus moorei) and soft-leaved (Toona ciliata) species

Developing leaves that are soft, with high concentrations of resources, can be particularly vulnerable to herbivore damage. Since a developing leaf cannot be very tough, given the constraints of cell expansion, the major form of protection is likely to be chemical defence. We investigated changes in concentration of herbivore resources (protein, carbohydrates and water) and putative defences (total phenolics, tannin activity, cyanogenic glycosides, alkaloids, cell wall, and leaf mechanics) across five leaf development stages of the soft-leaved Toona ciliata M. Roem. and the tough-leaved Nothofagus moorei (F. Muell.) Krasser. Chemical defences were predicted to be more highly developed in young than expanded leaves of both species, and to decline more in expanded leaves of N. moorei, which become tough and strong at maturity, than in the softer expanded leaves of T. ciliata. Resources and defences were dynamic within the developing leaves. Highest concentrations of protein were recorded in young leaves in both species, and highest levels of non-structural carbohydrate were recorded in young leaves of T. ciliata. Allocation to defence varied in both amount and type across leaf stages. In T. ciliata, there was an increase in chemical defence in expanded leaves (tannin activity, alkaloids). However, in N. moorei, increasing strength and toughness of developing leaves coincided with decreasing chemical defence, consistent with our hypothesis. For phenolics, this decrease was partly due to dilution by cell wall, but cyanogenic glycosides were present in young leaves and absent in fully mature leaves. These results are consistent with leaf toughness acting as an effective anti-herbivore defence, thereby reducing the need for investment in chemical defence.

Physiological Responses of Resistant and Susceptible Buffalograsses to <I>Blissus Occiduus</I> (Hemiptera: Blissidae) Feeding

The impact of Blissus occiduus Barber feeding on resistant ('Prestige') and susceptible ('378') buffalograsses, Buchloë dactyloides (Nuttall) Engelmann, was evaluated through measurement of carbon exchange rate, light and carbon assimilation (A-C(i)) curves, chlorophyll a fluorescence, and nonstructural carbohydrates. No significant differences in carbon exchange rates were observed between infested and control plants for 378 at 5 and 10 d after infestation; however, at 20 d after chinch bug introduction, significant differences in carbon exchange rates between infested and control 378 plants were detected. Carbon exchange rates were similar between infested and control Prestige plants at 5,10, and 20 d after infestation, suggesting that resistant plants can allocate energy for recovery from chinch bug injury. Significant differences in the photochemical efficiency of photosystem II (PSII) and the apparent photosynthetic electron transport ratio were observed between infested and control 378 plants, whereas, no significant differences in the photochemical efficiency of PSII and the electron transport ratio were detected between control and infested Prestige plants. Blissus occiduus-infested 378 and Prestige plants consistently had similar or higher levels of nonstructural carbohydrates compared with their respective control plants. These data suggest that both resistant and susceptible buffalograsses increase levels of nonstructural carbohydrates in response to B. occiduus feeding. This research also suggests compensatory photosynthesis takes place in Prestige but not in 378.

Physiological Responses of Resistant and Susceptible Buffalograsses to Blissus Occiduus (Hemiptera: Blissidae) Feeding

The impact of Blissus occiduus Barber feeding on resistant (‘Prestige’) and susceptible (‘378’) buffalograsses, Buchloë dactyloides (Nuttall) Engelmann, was evaluated through measurement of carbon exchange rate, light and carbon assimilation (A-Ci) curves, chlorophyll a fluorescence, and nonstructural carbohydrates. No significant differences in carbon exchange rates were observed between infested and control plants for 378 at 5 and 10 d after infestation; however, at 20 d after chinch bug introduction, significant differences in carbon exchange rates between infested and control 378 plants were detected. Carbon exchange rates were similar between infested and control Prestige plants at 5, 10, and 20 d after infestation, suggesting that resistant plants can allocate energy for recovery from chinch bug injury. Significant differences in the photochemical efficiency of photosystem II (PSII) and the apparent photosynthetic electron transport ratio were observed between infested and control 378 plants, whereas, no significant differences in the photochemical efficiency of PSII and the electron transport ratio were detected between control and infested Prestige plants. Blissus occiduus-infested 378 and Prestige plants consistently had similar or higher levels of nonstructural carbohydrates compared with their respective control plants. These data suggest that both resistant and susceptible buffalograsses increase levels of nonstructural carbohydrates in response to B. occiduus feeding. This research also suggests compensatory photosynthesis takes place in Prestige but not in 378.

Effects of nonstructural carbohydrate level and starch:sugar ratio on microbial metabolism in continuous culture of rumen contents

A dual flow continuous culture system was used to examine the effects of varying sugar as a proportion of sugar plus starch (NSC) at three concentrations of NSC on nutrient digestibility, ruminal fermentation and microbial growth. Diets contained 240, 280 and 330 g NSC/kg DM. At each NSC level, diets contained 29, 63 and 95 g sugar/kg DM. Corn grain and corn silage were the major starch sources. Liquid sugar blend (LSB) was the supplemental sugar source. Negative responses with interactions were seen at the 63 g sugar/kg DM level compared to no added sugar or 95 g sugar/kg DM in microbial growth, dry matter digested, protein digested, and total carbohydrate digested. Interactions resulted mostly because the negative responses to the 63 g sugar/kg DM were with the 240 and 280 g NSC/kg DM levels, but not with the 330 g NSC/kg DM level. Sugar addition depressed fiber digestion only with the 240 g NSC/kg DM level. At 330 g NSC/kg DM, all sugar substitutions were beneficial. Microbial responses were highest on the 330 g NSC/kg DM diet with 95 g sugar/kg DM, in which sugar made up 290 g/kg of the total NSC. Sugar additions at 95 g sugar/kg DM resulted in large increases in butyrate production. All sugar levels decreased acetate production but had little effect on propionate production.

Possible role of non-structural carbohydrates in flower induction in strawberry

SummaryFlower-induction is the event that initiates the transition of a vegetative apex into a floral apex in response to an environmental or developmental cue. Under flower-inducing conditions, biochemical or physiological changes can be recognised. One possible change that could occur is in sugar content. In this study, levels of non-structural carbohydrates (e.g., sucrose, glucose, fructose and starch) were measured in shoot tips, leaves and roots of strawberry (Fragaria ananassa cv. ‘Kordestan’) under flower bud-inducing conditions, and compared with non-induced plants. Runner plants were potted and grown for 4 weeks under non-inducing conditions (31º/25°C day/night; 16 h daylength). Half of the plants were then put under flower-inducing conditions (25°/15°C day/night; 8 h daylength) for 3 weeks. Samples for carbohydrate analysis were taken from induced and non-induced plants every 3 d over 3 weeks, and sucrose, glucose and fructose contents were determined by HPLC, and starch concentrations by the anthrone method. The most abundant soluble sugar, in all organs tested, was sucrose. Sucrose levels in shoot tips and leaves decreased at the beginning of the induction treatment, but soon increased to the levels recorded in non-induced plants. Fructose increased markedly in shoot tips of induced plants 3 d after the start of the short-day treatment, and declined thereafter. Starch contents in shoot tips, leaves and roots of non-induced strawberry plants were higher than those in induced plants on most sampling dates. From the results of this study, it appears that soluble carbohydrate contents in different organs of June-bearing strawberry may have a decisive role on flower-bud induction.

Functional role of anthocyanins in high‐light winter leaves of the evergreen herb Galax urceolata

High-light leaves of the evergreen herb Galax urceolata exhibit a striking color change from green to red during winter months due to anthocyanin synthesis in outermost mesophyll cells. Here we investigate three possible functions of this color change. To test the hypothesis that anthocyanins function as light attenuators, maximum photosystem II efficiency (F(v)/F(m)) of red and green leaves was measured during and after exposure to wavelengths either strongly or poorly absorbed by anthocyanin. To determine whether anthocyanins elevate radical-scavenging capacity, antioxidant activity of red and green leaves was assessed using the alpha,alpha-diphenyl-beta-picrylhydrazyl assay. Nonstructural carbohydrate levels were analyzed to test the hypothesis that anthocyanins function as a carbon sink. Declines in F(v)/F(m) under white and green light were significantly greater for green than red leaves, but were comparable under red light. Anthocyanin content positively correlated with antioxidant activity. Although levels of anthocyanins did not appear to be related to nonstructural carbohydrate concentration, high levels of sugars may be necessary for their photo-induction. Results suggest that anthocyanins function as light attenuators and may also contribute to the antioxidant pool in winter leaves.

A review of unlikely sources of excess carbohydrate in equine diets

Introduction Equines suffering from laminitis, insulin resistance, Equine Metabolic Syndrome, Cushing’s, osteochondrosis, and equine polysaccharide storage myopathy ( EPSM) require restriction of sugar, starch and/or fructan, which is collectively called Non Structural Carbohydrates (NSC). While there is a great deal of scientific literature in plant science journals regarding factors effecting NSC content of feed and forage, the information is not convenient to veterinarians. The nomenclature that plant scientists use may be unfamiliar to veterinarians, as well as the concepts central to plant physiology. Attempts by some veterinarians to give advice regarding more appropriate feed choices and pasture management practices to owners of carbohydrate intolerant equines may be based on incorrect assumptions, and incomplete understanding of the mechanisms governing NSC concentration in forage. This review is necessary to dispel some frequent misconceptions regarding NSC content of forage. Some forage that may be intuitively perceived as low in feed value, such as dead grass and weeds, may actually be high enough in NSC to trigger symptoms in susceptible animals. Grass founder has always been blamed on ‘lush’ grass. The term ‘lush’ is generally considered to mean green, vigorous, and well hydrated. Advice given by veterinarians on methods to avoid ‘lush’ grass may actually increase NSC concentration. This review will demonstrate how brown, dead or dying, desiccated grass can have surprisingly high levels of NSC, and explain the concepts of plant physiology that govern NSC accumulation in grass. This may explain onset of some previously mysterious cases of endocrinopathic laminitis, or worsening of symptoms in other diseases involving carbohydrate intolerance. There are some common misconceptions about the relative levels of Non Structural Carbohydrate (NSC) in horse feeds. While most horse owners recognize that molasses and grain are high in sugar and starch, they do not realize that excess NSC may be found in other portions of horse rations. This review of the NSC content of the non-grain portion of equine rations may provide practitioners and caretakers with information to fine-tune the diets of CHO intolerant equines.

Effects of elevated pCO 2 and/or pO 3 on C-, N-, and S-metabolites in the leaves of juvenile beech and spruce differ between trees grown in monoculture and mixed culture

Three and four-year-old saplings of beech ( Fagus sylvatica L.) and spruce ( Picea abies (L.) Karst.) grown in monoculture and mixed culture were exposed in phytotrons to (1) ambient air, (2) elevated pO 3, (3) elevated pCO 2, or (4) elevated pCO 2 plus elevated pO 3. After 5 months, the contents of soluble sugars, starch, soluble amino compounds, non-structural proteins (NSP), as well as reduced (GSH) and oxidized (GSSG) glutathione were determined in the leaves of both species in order to assess the effects of the gaseous regimes on primary metabolism. Elevated pO 3 did not affect sugar and starch levels in beech leaves in monoculture, but significantly increased sugar levels in beech leaves grown in mixed culture. In spruce needles, sugar levels tended to be enhanced in both culture types. Individual and combined exposure of elevated pCO 2 led to an increase in non-structural carbohydrate (soluble sugars plus starch) levels in beech and spruce leaves of both culture types. Differences in the responses of non-structural carbohydrate levels to elevated pCO 2 between beech and spruce were apparent from different contributions of sugars and starch to the increase in carbohydrate levels. Exposure to elevated pCO 2 and/or elevated pO 3 did not affect the levels of soluble amino compounds and NSP in beech leaves, but reduced amino compound levels in spruce needles of both culture types. Elevated pO 3 increased GSH levels in the leaves of both tree species in both culture types, while GSSG levels in monoculture were reduced in beech leaves, but significantly enhanced in spruce needles. Elevated pCO 2 reduced GSSG levels in beech and spruce leaves in monoculture, and GSH levels in spruce needles of both culture types. The combination of elevated pCO 2 and pO 3 increased GSSG levels in beech leaves of both culture types and in spruce needles in monoculture, but reduced GSH levels in spruce needles of both culture types. Apparently, under each gaseous regime, the culture type significantly altered primary metabolism of the leaves of beech and spruce.

Relationships between rumen volatile fatty acid concentrations and milk production in dairy cows: a literature study

Data from 20 research studies with 92 treatment means were summarized from the journals of dairy science and animal science 2000–2002. All studies were conducted with Holstein cows in Latin square or simple reversal design and included serial sampling of rumen fluid via cannula. Treatments included the effects of feeding various carbohydrate sources, corn milling byproducts, particle size of forage or grain, level of non-structural carbohydrates and the source and digestibility of forages. Studies included rations based on both stored forages and pasture. Simple statistics, correlation, linear regression and mixed model analysis assessing the random effect of study were used to describe the relationships between rumen and production parameters. Milk yield was most highly related to rumen concentrations of butyrate ( r 2 = 0.47) and propionate ( r 2 = 0.23). There was little or no relationship between milk yield and either rumen acetate or total VFA concentration. Milk yield was related positively to dry matter intake ( r 2 = 0.69) and negatively to days in milk ( r 2 = 0.25). An improvement in the regression of milk yield was obtained if the theoretical yield of ATP (to the host) per milliliter of rumen fluid was used as the independent variable in place of butyrate alone. Relationships between rumen volatile fatty acid concentrations and milk composition were moderate to weak. Content of milk fat (g/100 g) had a positive association with rumen acetate/propionate ratio ( r 2 = 0.26). Milk protein (g/100 g) had a negative relationship with rumen pH ( r 2 = 0.17) and a positive relation to days in milk. Rumen butyric acid concentration was positively related to dry matter intake ( r 2 = 0.28). Rumen butyric acid concentration had the strongest positive association with milk production and dry matter intake in this data set. The results suggest that in lactating cows increased energy intake is channeled largely through increases in rumen production of butyric and propionic acids and their yield of ATP to the host animal.