Concentration Of Total Soluble Carbohydrates Research Articles

Enhancing biohydrogen gas production in anaerobic system via comparative chemical pre-treatment on palm oil mill effluent (POME)

Biological hydrogen production using palm oil mill effluent (POME) as a carbon source through dark fermentation process has been suggested to be a promising bioenergy potential and enacts as alternative renewable energy source. Results have indicated that among various 1.5% (w/v) chemical pre-treatments (sodium hydroxide, NaOH; hydrochloric acid, HCl; sulphuric acid, H2SO4; phosphoric acid, H3PO4 and nitric acid, HNO3) on POME, using H3PO4 would generate maximum biohydrogen production of 0.193 mmol/L/h, which corresponded to a yield of 1.51 mol H2/mol TCconsumed with an initial total soluble carbohydrate concentration of 23.52 g/L. Among H3PO4 concentrations (1%–10%), the soluble carbohydrate content and the biohydrogen produced was highest and increased by 1.70-fold and 2.35-fold respectively at 2.5% (w/v), as compared to untreated POME. The batch fermentation maximum hydrogen production rate and yield of 0.208 mmol/L/h and 1.69 mol H2/mol TCconsumed were achieved at optimum pre-treatment conditions of pH 5.5 and thermophilic temperature (60 °C). This study suggests that chemical pre-treatment approaches manage to produce and improve the carbohydrate utilisation process further. Continuous fermentation in CSTR at the optimum conditions produce heightened 1.5-fold biohydrogen yield for 2.5% H3PO4 at 6 h HRT as compared to batch scale. Bacterial community via next-generation sequencing analysis at optimum HRT (6 h) revealed that Thermoanaerobacterium thermosaccharolyticum registered the highest relative frequency of 20.24%. At the class level, Clostridia, Bacilli, Bacteroidia, Thermoanaerobacteria, and Gammaproteobacteria were identified as the biohydrogen-producing bacteria in the continuous system. Insightful findings from this study suggest the substantial practical utility of dilute chemical pre-treatment in improving biohydrogen production.

Biochemical metabolism of young plants of Ucu\xfaba (Virola surinamensis) in the presence of cadmium

Virola surinamensis is a forest species widely distributed in the estuaries of the Amazon. These ecosystems are susceptible to contamination by Cadmium (Cd), indicating that the plant has strategies for tolerating this metal. The aim of this study was to assess the nitrogen and carbon metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium with the perspective of the phytoremediation of contaminated environments. The used experimental design was a completely randomized design with five Cd concentrations (0, 15, 30, 45, and 60 mg L− 1), for 60 days. In general, Cd did not affect nitrate concentration in the root but had a positive effect on leaves. The reduction of nitrate reductase (NR) in plants exposed to Cd was followed by a decrease in ammonia, total soluble amino acids (TSA), and total soluble proteins (TSP). Cd promoted an increase in the concentration of total soluble carbohydrates (TSC), proline, sucrose, and reducing sugars in the plants. The increase in TSC, sucrose and proline, suggests a metabolic regulatory mechanism of V. surinamensis against Cd stress.

Carbon nanofibers are bioaccumulated in Aphylla williamsoni (Odonata) larvae and cause REDOX imbalance and changes of acetylcholinesterase activity

Carbon-based materials have been considered very promising for the technological industry due to their unique physical and chemical properties, namely: ability to reduce production costs and to improve the efficiency of several products. However, there is little information on what is the level of exposure that leads to adverse effects and what kind of effects is expected in aquatic biota. Thus, the aim of the present study was to evaluate the toxicity of carbon nanofibers (CNFs) in dragonfly larvae (Aphylla williamsoni) based on predictive oxidative-stress biomarkers, antioxidant activity reduction and neurotoxicity. After ephemeral models' exposure to CNFs (48 h; at 500 μg/L), data have shown that these pollutants did not change larvae's nutritional status given the concentration of total soluble carbohydrates, total proteins and triglycerides in them. However, the levels of both nitric oxide and substances reactive to thiobarbituric acid (lipid peroxidation indicators) have increased and the antioxidant activity based on total thiol levels and on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (%) has reduced, and it suggests REDOX imbalance induction by CNFs. In addition, larvae exposed to these pollutants showed significant acetylcholinesterase activity reduction in comparison to the control group. Thus, the present study has brought further knowledge about how carbon-based materials can affect benthic macroinvertebrates and emphasized their ecotoxicological potential in freshwater environments.

Ratooned fennel relies on osmoregulation and antioxidants to damp seed yield decline with water limitation

Fennel (Foeniculum vulgare Mill.) is a medicinal species which has not been examined as a ratoon crop. Ratooning lessens the production intensity, but the ratooned fennel seed yield and physiological processes may differ with stand age, irrigation regime, and genotype. Eleven fennel genotypes were, thus, subjected to either limited or sufficient water supply for 6 years. For each year, the crop was harvested in early autumn to measure seed yield, yield components, dry mass, and essential oil. Besides, some physiological characteristics relevant to seed yield were studied in certain years. Results indicated a biphasic behavior in seed and essential oil yields of the majority of genotypes with maximum seed yields (ranging from 2514 to 2635 kg ha−1 in different genotypes) being obtained from the well-watered plants mainly in the 4th year of harvest. Taking the period of 6 years and the two irrigation regimes together, genotypes Yazd, Kashan, and Shiraz showed a better productive performance. Meaningful positive associations were found between the seed yield and such yield components as seeds/plant and certain physiological attributes, i.e., proline and total soluble carbohydrates concentrations, water potential, relative water content, and superoxide dismutase, catalase, and ascorbate peroxidase activities. Maximum seed yields (ranging from 1605 to 1704 kg ha−1) and essential oil yields (ranging from 33.3 to 45.5 kg ha−1) of plants grown under water-limited conditions were found in genotypes that benefited more from osmoregulative and antioxidative roles of proline and the antioxidative enzymes (i.e., Shiraz, Yazd, and Kashan) and, hence, were able to withstand better against water limitation. Considering such physiological capabilities, agronomic performance, and minimum stand age effects, we discovered for the first time that certain fennel genotypes could be proposed as potential resources for growing fennel as an alternative ratooned crop for low production intensity and sustainable cropping in arid climates.

Tolerance to waterlogging in Parkia gigantocarpa Ducke saplings

Cette étude se propose d’évaluer les réponses biochimiques des arbrisseaux de Parkia gigantocarpa devant l’engorgement d’eau. L’engorgement est appliqué en inondant les arbrisseaux dans des pots de 14 kg jusqu’à approximativement 5 cm au-dessus de la surface du sol. Le plan expérimental a été façonné aléatoirement et comprenait deux types d’application de l’eau (contrôle et engorgement) sur cinq périodes d’évaluation (après 0, 4, 8, 12 et 16 jours d’engorgement), avec cinq réplications par traitement. Amidon, saccharose, hydrates de carbone solubles totaux et protéines solubles totales ont été mesurés. Les arbrisseaux soumis à engorgement ont montré des réductions significatives des concentrations d’amidon (62,50 %) et de protéines solubles totales (40,98 %), en particulier dans les feuilles. L’engorgement a réduit la concentration de saccharose dans les feuilles (44,38 %), tandis que cette concentration a augmenté dans les racines (76,78 %). La concentration d’hydrates de carbone solubles a augmenté de 106,9 % dans les racines des plantes exposées à l’engorgement. Cette étude a démontré la sensibilité des arbrisseaux de Parkia gigantocarpa à l’engorgement.

Physiological and biochemical mechanisms of salinity tolerance in several fennel genotypes: Existence of clearly-expressed genotypic variations

Medicinal plants such as fennel (Foeniculum vulgare Mill.) are potent to be utilized as alternatives to conventional crop plants in the face of ever-increasing drought and salinity stresses in arid regions. However, scientific data on the physiological responses of F. vulgare to salt stress is scarce. Six F. vulgare genotypes were subjected to five concentrations of irrigation water NaCl (i.e. 0, 30, 60, 90, and 120 mM) in a pot experiment. Photosynthetic pigments of chlorophyll a (Chl-a) and b (Chl-b) and carotenoids (Cars) concentrations, leaf water potential (Pw), and plant height were decreased but Chl-a/b, proline concentration and ascorbate peroxidase (APX) activity were increased with increase in NaCl concentration. Averaged over NaCl concentrations, genotypes Urmia, Kashan and Isfahan out-numbered the other genotypes in terms of these traits. Relative water content (RWC), shoot K+ and Na+ concentrations, Na+/K+, superoxide dismutase (SOD) and catalase (CAT) activities, total soluble carbohydrates (TSC), H2O2 and malondialdehyde (MDA) concentrations, plant leaf area (LA), seed weight/plant and above-ground dry mass (DM) responded to salt in a genotype-specific manner, with genotypes Urmia, Kashan, and Isfahan tending to out-number the remaining genotypes in terms of the latter traits with the exception of MDA and Na+ concentrations. Results revealed that tolerance to modest salinity of genotypes Urmia, Kashan and Isfahan, manifested in smaller decreases in seed weight/plant and DM, was associated with their smaller Na+ but greater photosynthetic pigments, K+, proline and TSC concentrations, RWC, Pw, and antioxidant activities of the salt-stricken plants, compared to the remaining genotypes.

QUINOA AS A NEW LEAFY VEGETABLE CROP IN EGYPT

The present work was aimed to evaluate Chenopodium quinoa cultivar CICA (Chenopodium quinoa Willd. cv. CICA), in field experiments, as a new and non-traditional leafy crop in Egypt under saline (ECe 17.9 dSm-1) and non-saline (ECe 1.9 dSm-1) soil conditions. Production of biomass, some morphological, physiochemical and yield components traits were estimated at 40 days from sowing date. Biomass production of young quinoa shoot under saline soil was significantly higher by 25% than non-saline soil. Quinoa plants cultivated under saline soil also showed significant high performances for most of morphological traits. Although salinity led to accumulate Na+ concentrations in the leaves by six folds higher than that found in the leaves produced under non-saline soil conditions, but no significant reduction has been observed for K+ concentrations. Moreover, salinity was significantly increased magnesium concentrations in quinoa leaves. On the other hand, no significant increase has been detected of proline or total soluble carbohydrates concentrations in leaves of quinoa grown under saline soil as compared to non-saline soil. This clearly indicated that quinoa plants, during early growth stage, tended to utilize inorganic ions rather than organic solutes to regulate its osmotic potential under saline conditions. Chlorophyll a, chlorophyll b and carotenoid concentrations were significantly decreased under saline soil. Also, concentrations of crude fiber, crude fat and iron in the leaves of quinoa plants grown under saline soil conditions were significantly decreased. Meanwhile, salinity has no significant influence on crude protein concentrations. These results revealed that the quinoa has the ability to grow and produce considerable high leafy vegetable yield with good quality, in terms of high protein, in land unsuitable for conventional vegetable crops.

ECOFISIOLOGIA DE PROGÊNIE DE CUPUAÇUZEIRO SUBMETIDA A DÉFICIT HÍDRICO E REIDRATAÇÃO

The objective of this work was to evaluate the growth, biomass allocation and the ability of young plants of Theobroma grandiflorum to recover their water status and gas exchange after water deficit. Plants with 180 days, irrigated (control) and non-irrigated, were evaluated after water was withheld for 18 days, and after one, three and six days of irrigation resumption (rehydration). The drought reduced the production of biomass, and the leaves presented more significant reduction (28%). There was also a reduction in leaf area, plant height and stem diameter. Only the length of roots was not affected by soil water deficit. On the 18th, the leaf water potential of predawn (Ψam) of stressed plants was reduced to -3.07 MPa. With water deficit, significant reductions were observed in the relative water content in the predawn (25% reduction), stomatal conductance (78%) and sweating (90%). During rehydration, the water status of stressed plants was recovered after three days. Gas exchange was also recovered, but in a slower rate than water status. Under water deficit, the total soluble carbohydrate concentrations, total soluble amino acids and proline increased. Plants young are tolerant to moderate water deficit.

Fruit load in almond spurs define starch and total soluble carbohydrate concentration and therefore their survival and bloom probabilities in the next season

Abstract Nonpareil almonds trees have compact shoots, known as spurs. Spurs are the main bearing structure of many fruit trees. However, in almonds, spurs show alternate bearing and low winter survival if fruit load is high or if leaf area is low at the spur level. To better understand the source sink relationships that govern the effects of fruit load on spur survival and return bloom, a total of 1920 spurs with varying fruit load (non-fruiting spurs, one fruiting spurs, two fruiting spurs, and one fruiting spurs de-fruited at 40 and 70 days after full bloom) were labeled and tracked for two seasons in fully mature trees. Spur variables such as leaf area, total soluble carbohydrates (TSC), starch concentration, winter survival and return bloom were collected and analyzed with generalized linear mixed models and structural equation models. Starch concentration in non-fruiting spurs (excluding de-fruited spurs) was twice as high as starch concentration of fruiting spurs. Similarly, in the following season, the probabilities of survival and bloom in non-fruiting spurs were 55% and 61% higher than fruiting spurs, respectively. Structural equation modeling suggests that starch concentration in a spur is correlated with spur leaf area, number of fruits, fruit weight, and TSC. Thus, this work improves our understanding of return bloom and winter spur survival.

Does mycorrhizal colonisation vary between maize and sunflower under limitations to radiation source or carbohydrate sink?

The aim of this work was to analyse and compare indigenous arbuscular mycorrhizal colonisation (AMC) in relation to growth and total soluble carbohydrates (TSC) in two major, physiologically contrasting crop species: maize (Zea mays L.) and sunflower (Helianthus annuus L.). In order to promote contrasting TSC concentrations, we modified the radiation source by shading and the carbohydrate sink by manipulating reproductive sinks at different phenological stages during the grain-filling period in two field experiments. We assessed plant dry matter, TSC in stems, and root AMC from flowering until final harvest. AMC during the grain-filling period decreased in maize and increased in sunflower. A sink limitation increased AMC in maize, and reduced it in sunflower. A source limitation decreased AMC in both species, especially in sunflower. AMC was positively related to TSC in maize, but negatively in sunflower. The relationship was affected by shading in sunflower, but not in maize. In both species, a different linear model described the relationship between AMC and TSC in plants submitted to the removal of the reproductive organs. The results highlight the role of carbohydrates in mediating mycorrhizal formation, and show for the first time the opposite AMC–TSC relationships in maize and sunflower.

Enhancing the biodegradation process of cassava (<i>Manihot esculenta</i> Crantz) peels in dump site

Cassava (Manihot esculenta Crantz) peels have been implicated in serious environmental pollution. This study was aimed at investigating the effect of N.P.K (15:15:15) and microbial inoculants on the biodegradation process of cassava peels. Fresh cassava peels were subjected to biodegradation process for twenty weeks. The process was monitored by determining the moisture content, starch and total lipid using the official method of analysis of A.O.A.C, total protein by Kjeldahl method, total soluble carbohydrate by the modified Anthrone method, cellulose by the Nitric acid method, total cyanide by the modified alkaline picric acid method and pH using a Jowrey 3020 pH meter. The results of unsupplemented cassava peels and cassava peels supplemented with inorganic fertilizer N.P.K. (15:15:15) in experimental waste dump sites in which combinations of pure microbial cultures were used to inoculate cassava peels showed that pH increased from 5.89 to 7.03, total soluble carbohydrate concentrations decreased from 2.23% to 0.02%, protein from 5.54% to 0.78%, lipids from 3.00% to 0.1%, starch from 9.65% to 0.02%, cyanide from 0.11% to non-detectable level and cellulose from 8.80% to 0.20% at the end of the 20 weeks of investigation. This is an indication that the addition of inorganic fertilizer or microbial inoculants, or both enhanced the rate of biodegradation of cassava peels.Keywords: Biodegradation, Cassava peels, Dump site, Environmental pollution, Microbial Inoculant

Liming as an ameliorator of copper toxicity in black oat (Avena strigosa Schreb.)

ABSTRACTThis study aimed to assess the effect of liming as an ameliorator of copper (Cu) toxicity in black oats (Avena strigosa Schreb.) grown in soil with a sandy texture. The treatments were soil supplementation with increasing doses of lime (0.0, 0.5 and 1.0 g kg−1) and two of Cu (0 and 50 mg kg−1). Pre-germinated black oat seeds were sown for 30 days in the soil, subsequently, the plant height, root and shoot dry mass and concentration of total chlorophyll, chlorophylls a and b, carotenoids and total soluble carbohydrates and starch were analyzed. The dose of 50 mg kg−1 soil Cu caused a toxic effect on black oat plant growth and development, affected the internal distribution of nutrients, decreased the leaf chlorophyll concentration and increased the leaf concentration of total soluble carbohydrates and starch. Increasing lime doses ameliorated the toxic effects of Cu.

RESPONSE OF CERTAIN PHYTOCHEMICAL CONSTITUENTS IN SWEET PEPPER LEAVES TO SOME BIO-STIMULANTS UNDER TWO TYPES OF SALINITY

High salinity level of NaCl and CaCl2 (4000 mg/L) markedly increased whereas the low levels and its combination decreased electrolyte leakage percentage (E.L. %) in sweet pepper leaves as compared to the unstressed plants. In addition, application of all selected bio-regulators used at both applied levels, in most cases, alleviated the harmful effect of salinity on E.L. % especially ascorbic acid at 50 mg/L.
 Relative water content (RWC) and photosynthetic pigments were significantly increased thereafter decreased as salinity levels increased. In addition, CaCl2 at low level caused a great increase in RWC % followed by NaCl+CaCl2 and NaCl (2000 mg/L). While, pre-soaking seeds in both levels of the applied bio-stimulants caused a significant increase in RWC % and the photosynthetic pigments concentrations . In addition, AsA at 50 mg/L or SA at 75 mg/L was more effective in this respect as compared to the untreated plants.
 Ascorbic acid, proline, total phenols as well as total soluble carbohydrates concentrations in sweet pepper shoot were increased with increasing salinity levels from 2000 to 4000 mg/L of all salinity types. In addition, NaCl led to a great increase followed by NaCl+CaCl2 and CaCl2 as compared to the unstressed plants. In addition, pre-soaking seeds in SA, AsA, tocopherol and yeast extract at both levels increased ascorbic acid, proline, total phenols as well as total soluble carbohydrates concentrations under saline conditions. Moreover, AsA at 50 mg/L or SA at 75 mg/L was more effective in this respect as compared with the other treatments

Variations in α–, β–Amylase and α–Glycosidase Activities in Two genotypes of Wheat Under NACL Salinity Stress

Abstract Two wheat differing in salt sensitivity, was examined for osmolyte contents and activities of α-amylase, β-amylase and α-glucosidase enzymes involved in seeds germination, in absence as well as in presence of 100, 150, 200 and 300 mM NaCl. The inhibitory effects of NaCl differed, depending on the species tested. In wild wheat specie (Triticum monococcum), with reduced germination percentage and lower relative water content, the increase in NaCl concentration resulted in the decrease in endogenous level of proline, total soluble sugars and activities of the main enzymes involved in the germination process. In contrast, cultivated wheat specie (Triticum aestivum) seed in response to salt stress accumulated higher proline and total soluble carbohydrate concentrations which improved their water status and the enzyme activities involved in the germination process. Differential response of the different species of wheat to salt stress is governed by the accumulation of osmolytes in seeds.

English

Two wheat differing in salt sensivity, was examined for osmolyte contents and activities of a-amylase, b-amylase and a-glucosidase enzymes involved in seeds germination, in absence as well as in presence of 100, 150, 200 and 300 mM NaCl. The inhibitory effects of NaCl differed, depending on the species tested. In wild wheat specie (Triticum monococcum), with reduced germination percentage and lower relative water content, the increase in NaCl concentration resulted in the decrease in endogenous level of proline, total soluble carbohydrate and activities of the main enzymes involved in the germination process. In contrast, cultivated wheat specie (Triticum aestivum) seed in response to salt stress accumulated higher proline and total soluble carbohydrate concentrations which improved their water status and the enzyme activities involved in the germination process. Differential response of the different species of wheat to salt stress is governed by the accumulation of osmolytes in seeds. Key words: Salinity, amylases, glucosidases, wheat species.

Resistance of Winter Rye (Secale cereale L.) to Microdochium nivale Depends on Soluble Carbohydrate Content but not on Abscisic Acid Level

AbstractWinter rye plants of three Polish inbred lines and cv. Stach differing in Microdochium nivale resistance were studied relating to their frost and pink snow mould tolerance. The plants were prehardened at 12°C for 2 weeks and hardened at 2°C for 3 weeks. Control plants were grown in the greenhouse at 20°C. Frost resistance expressed as LT50 was determined for leaves and crowns of the hardened and control plants. Cold‐hardened were inoculated with mycelium of M. nivale and incubated for 35 days at 2°C in the dark. After this time, their pink snow mould resistance was evaluated and expressed as an average regrowth index (ARI). During 13 days of pathogenesis, changes in the total soluble carbohydrate (TSC) and ketose content were analysed. Moreover, changes in abscisic acid (ABA) and water content (WC) during 9 days of pathogenesis were determined. All analyses were carried out in leaves and crowns of inoculated and non‐inoculated (control) plants. Cold acclimation increased frost resistance of the leaves and crowns; however, the crowns were less frost tolerant than the leaves. In the studied lines, there was a negative correlation between frost tolerance of leaves and pink snow mould resistance of plants. Plants of lines more resistant to M. nivale exhibited higher TSC and ketose concentrations in the leaves and crowns as well as lower ABA levels in comparison with the less resistant plants. The role of ABA in the defence response of rye to pink snow mould is still unclear. It seems that ABA concentration does not determine rye resistance to M. nivale, although a higher level of this hormone could decrease it.

Compostos nitrogenados e carboidratos em sorgo submetido à salinidade e combinações de nitrato e amônio

The objective of this study was to evaluate the effects of combinations of nitrate and ammonium in the medium, on the accumulation of nitrogen compounds and carbohydrates, in the presence and absence of salinity in sorghum plants. CSF 20 genotype sorghum seeds, were grown in the greenhouse and supplied with a nutritive solution at three different concentrations of nitrate and ammonium (100% NO3-: 0% NH4+, 75% NO3-: 25% NH4+ e 0% NO3-: 100% NH4+) both in the presence and absence of NaCl. Salinity reduced the nitrate concentration in both leaves and stalks in treatments at 100:0 and 75:25. The accumulation of ammonium was higher in those plants, in both leaves and stalk, in the presence of NaCl. The levels of free amino acids in the leaves showed no change, whereas those in the stalk increased in the presence of salt and with the increase of ammonium. The concentration of free proline in both leaves and stalk was higher in plants under salinity. The total nitrogen content was higher in the leaves without, however, showing much change in the presence of salt. The concentration of total soluble carbohydrates was higher in those plants treated with salt, except in the stalk 0:100. Sucrose levels in the leaves were lower in the presence of NaCl and the increase in ammonium, while they were higher in the stalk at 75:25 NaCl. The starch content did not alter much with the different levels of nitrogen and salinity. It is concluded that NO-3 and NH4+ combinations in the medium affect the accumulation of nitrogen compounds and carbohydrates in the leaves and stalks of sorghum plants, both in the presence and absence of salinity.

Effects of foliar micronutrient application on osmotic adjustments, grain yield and yield components in sunflower (Alstar cultivar) under water stress at three stages

In order to study the effects of foliar micronutrient application under water stress, at three stages of growth, on prolinee and carbohydrate concentration, grain yield and yield components of sunflower (Alstar cultivar), a field experimental in split plot design with three replications was conducted in 2007. Alstar cultivar was comprised under water stress at three stages of growth (heading, flowering and grain filling) as main plot and seven micronutrient treatments, Fe, Zn, Mn, Fe+Zn, Fe+Mn, Zn+Mn and Fe+Zn+Mn, as sub-plots. Results showed that water stress at three stages of growth significantly decreased grain yield, biological yield, 1000 weight seeds, cap diameter and cap weight of sunflower (Alstar cultivar). The impact of water stress was more pronounced when applied at grain filling. Use of foliar micronutrient increased grain yield in water stress on the other hand, use of Mn foliar application had the highest positive effect on yield components and grain yield. Free prolinee and total soluble carbohydrate concentration were increased under water stress, at all of the three stages of growth. The highest concentration of these two components was found on the flowering stage. Key words: Water stress, micronutrient, grain yield, osmotic adjustment, sunflower.

Seasonal dynamics of soluble carbohydrates in rhizomes of Phragmites australis and Typha latifolia

Seasonal dynamics of concentrations of soluble carbohydrates (sucrose, glucose, fructose, and their sum denoted as total non-structural carbohydrates, TotCarb) in rhizomes of Phragmites australis (common reed) and Typha latifolia (cattail) were monitored in an irrigation channel and at Lake Kumaşır shores in Kahramanmaraş, Turkey, during the vegetation period 2004–2005. The soluble carbohydrate concentrations of the rhizomes of Phragmites australis and Typha latifolia were low at the beginning of the vegetation period; they reached their minima in February and March, respectively. Thereafter, soluble carbohydrate concentrations of both plants gradually increased until maximal values in August, thereafter decreasing gradually. Total soluble carbohydrate concentration in Typha latifolia rhizomes was higher than that of Phragmites australis during all months. Fructose prevailed in soluble carbohydrates throughout the season in Phragmites, followed by sucrose and glucose. In Typha latifolia the major sugar was glucose, followed by sucrose and fructose.

Rustificação de plantas de Eucalyptus dunnii Maiden e a relação entre as concentrações de carboidratos solúveis totais e de prolina foliar e a tolerância ao frio

O objetivo desta pesquisa foi avaliar o efeito da aclimatação sobre a tolerância ao frio de mudas de Eucalyptus dunnii Maiden (clone K-1007) e a relação entre a tolerância ao frio e as concentrações foliares de carboidratos solúveis totais e de prolina. O delineamento experimental utilizado foi de blocos ao acaso com quatro repetições. Os tratamentos consistiram de diferentes períodos de aclimatação (0, 7, 21 e 42 dias de exposição às plantas a temperaturas diurnas de 5 ºC e noturnas de 1 ºC). Após cada período de aclimatação, as mudas foram submetidas a quatro gradientes de temperatura negativas (-2 ºC, -4 ºC, -6 ºC e -8 ºC), por 3 h cada gradiente. Após cada período de aclimatação, foram avaliadas as concentrações foliares de carboidratos solúveis totais e prolina. Após cada gradiente de temperatura negativa, foram coletadas amostras foliares para a avaliação da temperatura letal de 50% (TL50). Os dados foram submetidos à análise de regressão linear e teste de correlação de Pearson. As mudas de E. dunnii apresentaram aumento nos teores de carboidratos solúveis até 28 dias de aclimatação; após esse período, as concentrações permaneceram estáveis. Observou-se correlação negativa entre a temperatura letal de 50% (TL50) e a concentração de carboidratos solúveis totais no tecido foliar. Dessa forma, observou-se aumento na tolerância ao frio com o aumento dos teores de carboidratos solúveis no período de aclimatação de até 28 dias.