Alkaline Invertase Activity Research Articles

Long-Term Soil Drought Limits Starch Accumulation by Altering Sucrose Transport and Starch Synthesis in Sweet Potato Tuberous Root.

In this study, the influences of long-term soil drought with three levels [soil-relative water content (SRWC) (75 ± 5)%, as the control; SRWC (55 ± 5)%, mild drought; SRWC (45 ± 5)%, severe drought] were investigated on sucrose-starch metabolism in sweet potato tuberous roots (TRs) by pot experiment. Compared to the control, drought stress increased soluble sugar and sucrose content by 4-60% and 9-75%, respectively, but reduced starch accumulation by 30-66% through decreasing the starch accumulate rate in TRs. In the drought-treated TRs, the inhibition of sucrose decomposition was attributed to the reduced activities of acid invertase (AI) and alkaline invertase (AKI) and the IbA-INV3 expression, rather than sucrose synthase (SuSy), consequently leading to the increased sucrose content in TRs. In addition, starch synthesis was inhibited mainly by reducing ADP-glucose pyrophosphorylase (AGPase), granular starch synthase (GBSS) and starch branching enzyme (SBE) activities in TRs under drought stress, and AGPase was the rate-limiting enzyme. Furthermore, soil drought remarkably up-regulated the IbSWEET11, IbSWEET605, and IbSUT4 expressions in Jishu 26 TRs, while it down-regulated or had no significant differences in Xushu 32 and Ningzishu 1 TRs. These results suggested that the sucrose-loading capability in Jishu 26 TRs were stronger than that in Xushu 32 and Ningzishu 1 TRs. Moreover, IbA-INV3, IbAGPS1, IbAGPS2, IbGBSSI and IbSBEII play important roles in different drought-tolerant cultivars under drought stress.

Response of selected microbial strains and their consortia to the presence of automobile paints: Biofilm growth, matrix protein content and hydrolytic enzyme activity

The goal of the current study was to examine the effects of pollutants (White color – CP; Metallic red color – FM; Thinner – CN; Thinner for rinsing paint – MF; Basic color (primer) – FH) originating from the automotive industry on the biofilm growth, matrix protein content, and activity of the hydrolytic enzymes of selected microbial strains in laboratory conditions that mimic the bioreactor conditions. The chosen microorganisms (bacteria, yeasts, and fungi) were isolated from automotive industry wastewater. Pure microbe cultures and their consortia were injected into AMB Media carriers and developed into biofilms. The use of AMB media carriers has been linked to an increase in the active surface area colonized by microorganisms. Afterwards, the carriers were transferred to Erlenmeyer flasks with nutrient media and pollutants at a concentration of 200 μL/mL. The current study found that, depending on the microbial strain, development phase, and chemical structure, the assessed pollutants had an inhibitory or stimulatory influence on the growth of single cultures and their consortia. Statistical analysis found positive correlations between the protein content in the matrix and the biofilm biomass of Rhodotorula mucilaginosa and consortia in CP and FH media, respectively. The proteolytic activity of Candida utilis was very pronounced in media with MF and CN. The best alkaline phosphatase activity (ALP) was achieved in the CN medium of R. mucilaginosa. Acid invertase activity was the highest in the FM and CP media of Escherichia coli and consortia, respectively, whereas the highest alkaline invertase activity was measured in the MF medium of E. coli. A positive correlation was confirmed between ALP and the biofilm biomass of R. mucilaginosa in CP and CN media, as well as between ALP and the biofilm biomass of Penicillium expansum in FM medium. The findings provide novel insights into the extracellular hydrolytic activity of the investigated microbial strains in the presence of auto paints, as well as a good platform for subsequent research into comprehensive biofilm profiling using modern methodologies.

Strategies to Apply Water-Deficit Stress: Similarities and Disparities at the Whole Plant Metabolism Level in Medicago truncatula.

Water-deficit stresses such as drought and salinity are the most important factors limiting crop productivity. Hence, understanding the plant responses to these stresses is key for the improvement of their tolerance and yield. In this study M. truncatula plants were subjected to 250 mM NaCl as well as reduced irrigation (No-W) and 250 g/L polyethylene glycol (PEG)-6000 to induce salinity and drought stress, respectively, provoking a drop to −1.7 MPa in leaf water potential. The whole plant physiology and metabolism was explored by characterizing the stress responses at root, phloem sap and leaf organ level. PEG treatment led to some typical responses of plants to drought stress, but in addition to PEG uptake, an important impairment of nutrient uptake and a different regulation of carbon metabolism could be observed compared to No-W plants. No-W plants showed an important redistribution of antioxidants and assimilates to the root tissue, with a distinctive increase in root proline degradation and alkaline invertase activity. On the contrary, salinity provoked an increase in leaf starch and isocitrate dehydrogenase activity, suggesting key roles in the plant response to this stress. Overall, results suggest higher protection of salt-stressed shoots and non-irrigated roots through different mechanisms, including the regulation of proline and carbon metabolism, while discarding PEG as safe mimicker of drought. This raises the need to understand the effect at the whole plant level of the different strategies employed to apply water-deficit stress.

The Influence of Endogenous Sugar on Potato Tuberization in In Vivo Conditions

Sugar (S) and nitrogen (N) play critical roles in potato tuberization and development, which determines the number, size, and yield of tubers. However, the dynamic models of endogenous sugar and nitrogen during tuberization and development are poorly understood. A pot experiment was performed with the potato cultivar Jizhangshu 12. Tuber and leaf samples were continuously taken to detect the morphological changes in stolon or tuber during tuberization and development. Sugar, starch, nitrogen content, and sucrose metabolism-related enzyme activity were measured. Results showed that the starch, fructose, and sucrose content and S/N ratio in leaves decreased significantly, while significant increases were observed in the activities of alkaline invertase (ALI), sucrose synthetase (SS), and sucrose phosphate synthase (SPS), and the ratios of glucose/sucrose and glucose/fructose from stolon hook initiation to subapical swelling. In contrast, nitrogen content and S/N ratio decreased significantly and starch and glucose content, AI (acid invertase), ALI, SS, and SPS activities, and glucose/sucrose ratio in stolons increased significantly. When the diameter from the stolon subapical swelling to the tuber reached 3.0 cm, starch content and glucose/sucrose and glucose/fructose ratios in leaves and tubers, and contents of fructose and sucrose and the activities of AI and SPS in tubers fluctuated; the S/N ratio in both leaves and tubers increased significantly; the activity of SPS in leaves, and activities of ALI and SS in tubers declined significantly. When the tuber diameter increased from 3.0 to 6.0 cm, the content of starch, sucrose, fructose, and total nitrogen, the activities of AI, ALI, and SPS, and the S/N ratio in leaves increased, while the ratios of glucose/sucrose and glucose/fructose showed an opposite trend; the changes in tubers were slight. We conclude that the content of sugar and total nitrogen and the balance of sugar and nitrogen in leaves and stolons changed significantly at tuberization and gradually thereafter. The significant increases in the ratios of glucose/fructose and glucose/sucrose in leaves could be used as indirect indicators to determine tuberization. The ratio of S/N could replace that of nonstructural carbohydrate/nitrogen to characterize potato tuberization and development.

Foliar treatment of potassium nitrate modulates the fermentative and sucrose metabolizing pathways in contrasting maize genotypes under water logging stress.

The effect of potassium nitrate on the status of fermentative and sucrose metabolizing pathways was studied in two maize (Zea mays L.) genotypes, viz., LM 5 (relatively susceptible to flooding) and I 167 (relatively tolerant to flooding) under water logging stress. The higher increase in pyruvate decarboxylase, alcohol dehydrogenase and aldehyde dehydrogenase activities in the hypoxic roots of I 167 seedlings over LM 5 showed the former's efficient tolerance mechanism towards anaerobic conditions. Foliar application of KNO3 reduced these enzymatic activities in the roots of both the genotypes. The shoots of I 167 seedlings also showed a parallel increase in alcohol dehydrogenase and pyruvate decarboxylase activities under water logging stress. These enzymatic activities, however, remained unaffected in shoots of water logged LM 5 seedlings. There was a higher decrease in acid and alkaline invertase activities in the hypoxic roots of I 167 seedlings. KNO3 treatment led to higher acid invertase activity in roots of I 167 seedlings than those of LM 5. Sucrose synthase (synthesis) and sucrose phosphate synthase activities decreased, but sucrose synthase (breakdown) activity increased in the roots of both the genotypes, during water logging. KNO3 increased sucrose synthesizing activities with a parallel increase in the sucrose content of the roots. Sucrose synthesis was comparatively unaffected in I 167 shoots under water logging stress while LM 5 shoots showed higher reduction in its sucrose synthase (synthesis) and sucrose phosphate synthase activities. It may thus be concluded that KNO3 induced a network of reactions for improving water logging tolerance. The nitrate ions acted as an alternate electron acceptor and thus reduced the activities of fermentative enzymes. It promoted the funneling of sugars into the glycolytic pathway by inducing the activities of acid and alkaline invertases in the roots and shoots of maize genotypes. It also directed the hexoses towards biosynthetic pathway by increasing the activities of sucrose synthesizing enzymes.

Effect of detergents on alkaline invertase and alkaline phosphatase activity of fungi Mucor plumbeus Bonord, 1864, Aspergillus Niger Tiegh, 1867 and Trichoderma harzianum Rifai, 1969

Due to their diverse metabolic potential, many filamentous fungi have a great ability for degradation of different waste substances. The present research was aimed to investigate ability of fungi Mucor plumbeus, Aspergillus Niger and Trichoderma harzianum, isolated from sewer and industrial waste water, to conduct degradation of high concentrations of commercial detergent (0.3%). Within enzyme extracts of samples taken during period of 3-16 days, activity of alkaline invertase and alkaline phosphatase was followed spectrophotometrically at room temperature. Obtained results proved that all examined fungi affected degradation of detergent. Quality (inhibition/stimulation) and quantity of action of detergent on activity of investigated enzymes depended on fungal species and incubation period. The highest inhibiting effect of detergent was recorded on 9th day of incubation in samples of T. harzianum and A. Niger, while its most obvious stimulating effect was noticed on 3rd day of incubation in samples of T. harzianum and M. plumbeus. Investigated fungi can be used for purification of waste water containing high concentrations of detergent.

Detection of enzymes produced by lactic acid bacteria isolated from traditionally made Serbian cheese and their role in the formation of its specific flavor

Nine species (sixteen isolates) of lactic acid bacteria (LAB) isolated from traditionally made Serbian cheese were evaluated for their enzymatic activities in order to select indigenous strains of technical interest for the manufacture of cheese. These strains were selected based on their previously determined biochemical and physiological characteristics, as well as their antimicrobial activity, and were identified as Lactococcus lactis subsp. lactis (one isolate), Lc. lactis subsp. lactis biovar. diacetylactis (five isolates), Lactobacillus fermentum (two isolates), Lb. plantarum (one isolate), Lb. brevis (one isolate), Enterococcus faecalis (three isolates), E. faecium (one isolate), E. durans (one isolate) and E. hirae (one isolate). The enzymatic activities (acid and alkaline invertases, alkaline phosphatase, alkaline protease, a-amylase) were measured by using the spectrophotometric method. The results indicated that all Lactobacillus isolates showed protease, amylase, and alkaline phosphatase activities, while the activities of acid and alkaline invertases were not observed. The Lactococcus isolates showed protease, acid invertase and alkaline phosphatase activities, except the KGPMF50 isolate, which showed no alkaline phosphatase activity. The tested Enterococcus isolates showed weakly and strain-specific enzymatic activity. The results indicated that the enzymes produced by the investigated strains have a role in the formation of the specific flavor of cheese and that these isolates, especially Lactobacillus isolates, showed the potential for use in the dairy industry or applied biotechnology.

Effect of osmo priming on sucrose metabolism in spring maize, during the period of grain filling, under limited irrigation conditions.

The present study was undertaken to study the effect of osmo priming on sucrose metabolism of spring maize, under limited irrigation conditions. Osmo priming increased the activities of acid invertase, alkaline invertase and sucrose synthase (cleavage) and the contents of reducing sugars and starch in the grains of stressed plants. There was also an increase in sucrose phosphate synthase activity with a parallel increase in sucrose content in leaves of stressed plants in comparison with those of hydro priming treatment. It showed that osmo priming helped in improving sucrose phosphate synthase activity in leaves of plants, leading to higher sucrose content, under stress conditions.

Effects of chilling stress on the accumulation of soluble sugars and their key enzymes in Jatropha curcas seedlings.

As osmolytes and signaling molecules, soluble sugars participate in the response and adaptation of plants to environmental stresses. In the present study, we measured the effect of chilling (12°C) stress on the contents of eight soluble sugars in the leaves, cotyledons, stems, and roots of Jatropha curcas seedlings, as well as on the activities of eight rate-limiting enzymes that are critical to the metabolism of those soluble sugars. Chilling stress promoted both starch hydrolysis and soluble sugar accumulation.The soluble sugar contents of the leaves and cotyledons were affected more than that of the stems and roots. Meanwhile, the activities of the corresponding metabolic enzymes (e.g., β-amylase, uridine diphosphate glucose phosphorylase, and sucrose phosphate synthase) also increased in some organs. The gradual increase of soluble neutral alkaline invertase activity in the four studied organs suggested that sucrose catabolic production, such as glucose and fructose, was especially important in determining resistance to chilling stress and hexose signal transduction pathway. In addition, the substantial accumulation of raffinose family oligosaccharides and increase in corresponding metabolic enzyme activity suggested that galactinol and raffinose play an important role in determining the chilling resistance of J. curcas. Together, these findings establish a foundation for determining the relationship between the chilling resistance and soluble sugar accumulation of J. curcas and for investigating the mechanisms underlying sugar signaling transduction and stress responses.

Production of biotechnological useful metabolites by Mucor racemosus in Czapek-Dox liquid media supplemented with synthetic detergent

The capacity of native isolate Mucor racemosus to produce several potentially useful metabolites in a liquid Czapek-Dox medium supplemented with powder anionic-type detergent MERIX (Henkel, Serbia) at concentrations of 0.3% (D3) and 0.5% (D5) was examined in this study. The changes of pH values, the total protein content, activities of acid and alkaline invertase, ?-amylase, as well as biomass dry weight were evaluated during fungal growth from inoculation until the 16th day. In addition, the qualitative and quantitative amino acids content of 16 days old fermentation broth was determined by HPLC. D3 considerably enhanced the biomass dry weight (43%), ?-amylase activity (49.59%) and the quantity of arginine (40.38%), and also influenced the production of a high amount of proteins (5.32 g/L). D5 significantly enhanced the biomass dry weight (53%), the quantity of arginine (119.09%) and alanine (192.79%) and induced the production of valine, serine and glutamate. In the D5 medium, ?-amylase retained 100% of its activity. The acid and alkaline invertase activity was moderately inhibited by D3 and D5. The obtained results may have considerable biotechnological, industrial and environmental potential.

Potassium deficiency limits reproductive success by altering carbohydrate and protein balances in cotton (Gossypium hirsutum L.)

Reproductive success in higher plants requires a lot of energy and substance provided by carbohydrate and protein metabolism, and potassium (K) plays an important role in carbohydrate and protein metabolism. However, it is unclear whether K deficiency limits reproductive success by disturbing carbohydrate and protein metabolism. The objectives of this study were to explore the effects of K deficiency on carbohydrate and protein metabolism in subtending leaves, phloem and pistils, and their relationship with reproductive success. A cotton cultivar DP0912 was grown in K-deficient (0mMK+) and K-sufficient (6mMK+) nutrient solution in growth chambers. Results showed that Pn of the subtending leaves was decreased under K deficiency, but sucrose, starch and free amino acid contents were markedly increased in the K-deficient leaves, because K deficiency limited the translocation of sucrose and amino acid in phloem. As a result, sucrose and free amino acid contents were reduced by 47.3% and 51.8% in the K-deficient pistils than K-sufficient pistils, which led to further decreases in starch and protein accumulation in the K-deficient pistils. Glucose content was also reduced by 53.1% in the K-deficient pistils than K-sufficient pistils, due to the decreased acid and alkaline invertase activities, since sucrose synthase activity was not affected. Lastly, soluble carbohydrate and ATP contents were lower in the K-deficient pistils than K-sufficient pistils, similarly to the changes of pollen tube growth rate and seed set efficiency. It was concluded that the lower carbohydrate and ATP contents in the K-deficient pistils could not meet the energy requirements of pollen tube growth and seed set. Moreover, protein imbalance also limited pollen tube growth. Those changes resulted in lower seed set efficiency to limit reproductive success.

Short versus long term effects of cyanide on sugar metabolism and transport in dormant walnut kernels

Tree seed dormancy release by cold stratification accompanies with the embryo increased gluconeogenesis competence. Cyanide also breaks seed dormancy however, integrated information about its effects on carbon metabolism is lacking. Accordingly, the impacts of HCN on germination, lipid gluconeogenesis and sugar transport capacity of walnut (Juglans regia L.) kernels were investigated during 10-days period prior to radicle protrusion. HCN increased walnut kernel germination and within four days of kernel incubation, hastened the decline of starch, reducing and non-reducing sugars and led to greater activities of alkaline invertase and glucose-6-phosphate dehydrogenase. From four days of kernel incubation onwards, starch and non-reducing sugars accumulated only in the HCN treated axes. Cyanide also increased the activities of phosphoenolpyruvate carboxykinase and glyoxysomal succinate oxidase and led to greater acid invertase activity during the aforementioned period. The expressions of both sucrose transporter (JrSUT1) and H+-ATPase (JrAHA1) genes especially in cotyledons and H+-ATPase activity in kernels were significantly enhanced by exposure to cyanide. Thus in short-term HCN led to prevalence of carbohydrate catabolic events such as oxidative pentose phosphate pathway and possibly glycolysis in dormant walnut kernels. Long-term effects however, are increased gluconeogenesis and enhanced sugar transport capacity of kernels as a prerequisite for germination.

Effects of Soil Salinity on Sucrose Metabolism in Cotton Fiber.

Cotton (Gosspium hirsutum L.) is classified as a salt tolerant crop. However, its yield and fiber quality are negatively affected by soil salinity. Studies on the enzymatic differences in sucrose metabolism under different soil salinity levels are lacking. Therefore, field experiments, using two cotton cultivars, CCRI-79 (salt-tolerant) and Simian 3 (salt-sensitive), were conducted in 2013 and 2014 at three different salinity levels (1.15 dS m-1 [low soil salinity], 6.00 dS m-1 [medium soil salinity], and 11.46 dS m-1 [high soil salinity]). The objective was to elucidate the effects of soil salinity on sucrose content and the activity of key enzymes that are related to sucrose metabolism in cotton fiber. Results showed that as the soil salinity increased, cellulose content, sucrose content, and sucrose transformation rate declined; the decreases in cellulose content and sucrose transformation rate caused by the increase in soil salinity were more in Simian 3 than those in CCRI-79. With increase in soil salinity, activities of sucrose metabolism enzymes sucrose phophate synthase (SPS), acidic invertase, and alkaline invertase were decreased, whereas sucrose synthase (SuSy) activity increased. However, the changes displayed in the SuSy and SPS activities in response to increase in soil salinity were different and the differences were large between the two cotton cultivars. These results illustrated that suppressed cellulose synthesis and sucrose metabolism under high soil salinity were mainly due to the change in SPS, SuSy, and invertase activities, and the difference in cellulose synthesis and sucrose metabolism in fiber for the two cotton cultivars in response to soil salinity was determined mainly by both SuSy and SPS activities.

Reduced Sink Activity in Growing Shoot Tissues of Maize under Salt Stress of the First Phase may be Compensated by Increased PEP‐Carboxylase Activity

AbstractThe effects of salt stress (100 mm NaCl for 6 days) on growing tissues (shoot apex, growing leaf segments, root tips) of young maize plants (Zea mays L. cv. Pioneer 3906) were investigated in comparison to an unsalinized control, focusing on assimilate supply from source leaves and the activity of sucrolytic enzymes in the sink tissues. The objectives were to test whether (i) phloem unloading in growing tissues is mainly symplastic, (ii) salinity reduces sink activity, determined either as sucrose synthase activity (indicator for the symplastic pathway) or as acid invertase activity (indicator for the apoplastic pathway), and (iii) PEP‐carboxylase activity is increased under salinity to compensate for reduced sink activity. For growing tissues of young maize shoots, it can be assumed that phloem transport of sucrose is mainly driven by symplastic unloading into the sink cells. In maize root tips, both, apoplastic and symplastic pathways, contributed to carbohydrate supply to the sink cells. The activity of acid invertase in growing shoot tissues was very low, and the alkaline invertase contributed less than 10 % to the cytoplasmic sucrolytic activity. Salt stress of the first phase (mainly osmotic stress) caused a significant inhibition of acid invertase activity in the growing leaf segments and in the root tips, which was also true for alkaline invertase activity in the root tips as well as for sucrose synthase activity in root tips and shoot apex. The decrease of sucrose synthase activity in shoot apex might be particularly detrimental for the plant growth, as this tissue with a high cell division rate relied entirely on cytoplasmic enzyme activities. Under salt stress, PEP carboxylase activity was significantly increased in growing leaves and the shoot apex of maize, whereas no significant effect was observed in the root apex. In conclusion, PEP carboxylase can have an anaplerotic function supporting the demand for metabolites in growing shoot tissues of young maize plants under salt stress. In root tips, an additional supply of organic acids to the tricarboxylic acid cycle is probably not needed, as sucrolytic sink activity, which was high even under saline conditions, can meet the demand of the sink cells.

Nitrogen forms modulate effects of benzothiadiazole and arbutin on cucumber sugar metabolism

The effect of benzothiadiazole (BTH) and arbutin (ARB) on sugar metabolism and plant fitness in cucumber growing hydroponically in media with different doses of NO3 - and urea as nitrogen sources (100 % NO3 -, 75 % NO3 - + 25 % urea, and 50 % NO3 - + 50 % urea) was studied on the 7th and 14th day after the treatment. The glucose, sucrose, and chlorophyll (Chl) content, acid and alkaline invertases and lactate dehydrogenase activities, as well as leaf area of the 3rd and 5th leaves were determined. Urea changed the plant sugar metabolism in a dose-, time- and leaf-age-dependent manners and influenced a cucumber response to the BTH and ARB treatments. The BTH caused a significant cessation of growth, a decrease in Chl content, a reduction of leaf area, and an enhancement of lactate dehydrogenase and alkaline invertase activities. In the older leaves of the BTH-treated plants, a high accumulation of glucose and sucrose was found. At the lower dose of urea, the metabolic changes were limited. In the ARB-treated plants, the Chl content remained unchanged in all the nitrogen variants. In these plants, decrease in glucose and sucrose content and in both invertase activities was observed mainly in younger leaves of the plants grown on the high dose of urea. The ARB improved the fitness of the cucumber plants grown in the presence of urea.

Arbutin- and benzotiadiazole-mediated cucumber response to Pseudomonas syringae pv. lachrymans infection in carbohydrate metabolism

The effect of exogenous arbutin (ARB) or benzotiadiazole (BTH) on carbohydrate metabolism in cucumber infected with Pseudomonas syringae pv. lachrymans was studied. Glucose, sucrose, chlorophyll and carotenoid levels, acid and alkaline invertase and lactate dehydrogenase activities at the local (3rd, inoculated leaf) and systemic (5th, non-inoculated leaf) levels were determined. ARB limited disease symptom development to an extent similar to BTH. It was shown that both compounds effectively protected cucumber plants against this hemibiotrophic pathogen, however, the mechanisms of their activity are different. In the ARB-treated plants following the infection younger leaves were in better condition than BTH-treated ones due to more effective carbohydrate metabolism. Moreover, as opposed to BTH, ARB was not cytotoxic for plant tissues.

Differential response of wild and cultivated wheats to water deficits during grain development: changes in soluble carbohydrates and invertases.

Wheat, staple food crop of the world, is sensitive to drought, especially during the grain-filling period. Water soluble carbohydrates (WSCs), stem reserve mobilization and higher invertase activity in the developing grains are important biochemical traits for breeding wheat to enhance tolerance to terminal drought. These traits were studied for three accessions of Triticum dicoccoides(a tetraploid wheat progenitor species) - acc 7054 (EC 171812), acc 7079 (EC 171837) and acc 14004 (G-194-3M-6M) selected previously on the basis of grain filling characteristics. Check wheat cultivars- PBW-343 (a popular bread wheat cultivar for irrigated environments) and C-306 (widely adapted variety for rain-fed agriculture) were also included in this set. Analysis of variance revealed significant genotypic differences for the content of water soluble carbohydrates, activity of acid invertase and alkaline invertase. Acc 7079 was found to be a very efficient mobilizer of water soluble carbohydrates (236.43mgg(-1) peduncle DW) when averaged over irrigated and rain-fed conditions. Acid invertase activity revealed marked genotypic differences between wild and cultivated wheats. Alkaline invertase activity was highest in Acc 7079 when pooled across both the environments. On the whole, acc 7079 qualifies as a suitable donor for enhancing tolerance of bread wheat to terminal drought. The association of physio-biochemical differences observed with grain filling attributes on one hand and molecular markers on the other could be of use in improving wheat for water stress conditions.

CARBOHYDRATE METABOLISM IN INFLORESCENCES OF EPIDENDRUM IBAGUENSE

The purpose of this work was to determine changes in the carbohydrate content and sucrolytic activity in flower structures of Epidendrum ibaguense. Inflorescences were harvested at the different stages of development: 0 – mature closed bud, 1 – fully opened flower, 2 – senescence onset (red petals and twisted red labellum), 3 – wilted and senescent flower. Levels of total soluble sugar, reducing and non-reducing sugars and starch, as well as acid and alkaline invertase and sucrose synthase activities were determined. In inflorescences at the stage 3 the consumption of carbohydrates was observed during their postharvest life, as both carbohydrate types decreased along with time. The levels of soluble sugars, non-reducing sugars and starch did not differ over time in the inflorescence at stages 0, 1 and 2. Reducing sugar content decreased in flowers at stages 0, 1 and 3. No significant difference in starch content was detected among stages 0 to 2; starch showed an increase in senescing flowers. Soluble acid invertase was the main enzyme active throughout flower ageing. Sucrose synthase activity was kept low, with a relative increasing during senescence, which coincided with the highest levels of starch. In conclusion, carbohydrate metabolism varied along with the stage of development and the postharvest life of inflorescences of E. ibaguense.

Trehalose Accumulation in Wheat Plant Promotes Sucrose and Starch Biosynthesis

Seeds of Triticum aestivum L. (cv. Sakha 93) were sown in pots and grown under controlled conditions in growth chamber. The plants were irrigated with half strength of Hoaglad solution without or with 10 or 30 µM validamycin A, a potent inhibitor of trehalase. Plants were collected at three different stages of growth (17, 24 and 31 DAP). Validamycin A decreased the activity of trehalase which leads to the accumulation of trehalose in shoot and root of wheat plants. Raising trehalose level in the plant tissues was accompanied by increase in the sucrose content and starch content of the shoot. The increased contents in sucrose and starch were mainly attributed to the increased levels of trehalose. The effect of trehalose on the sucrose degrading enzymes (alkaline and acid invertases and sucrose synthase) showed stimulation of alkaline invertase activity and inhibition of acid invertase and sucrose synthase. The opposite behavior of sucrose degrading enzymes suggests a regulation mechanism controlling the sucrose pool.

Effects of Increased Night Temperature on Cellulose Synthesis and the Activity of Sucrose Metabolism Enzymes in Cotton Fiber

Temperature is one of the key factors that influence cotton fiber synthesis at the late growth stage of cotton. In this paper, using two early-maturing cotton varieties as experimental materials, night temperature increase was stimulated in the field using far-infrared quartz tubes set in semi-mobile incubators and compared with the normal night temperatures (control) in order to investigate the effects of night temperature on the cotton fiber cellulose synthesis during secondary wall thickening. The results showed that the activity of sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) quickly increased and remained constant during the development of cotton fiber, while the activity of acid invertase (AI) and alkaline invertase (NI) decreased, increased night temperatures prompted the rapid transformation of sugar, and all the available sucrose fully converted into cellulose. With night temperature increasing treatment, an increase in SuSy activity and concentration of sucrose indicate more sucrose converted into UDPG (uridin diphosphate-glucose) during the early and late stages of cotton fiber development. Furthermore, SPS activity and the increased concentration of fructose accelerated fructose degradation and reduced the inhibition of fructose to SuSy; maintaining higher value of allocation proportion of invertase and sucrose during the early development stages of cotton fiber, which was propitious to supply a greater carbon source and energy for cellulose synthesis. Therefore, the minimum temperature in the nightime was a major factor correlated with the activity of sucrose metabolism enzymes in cotton fiber. Consequently, soluble sugar transformation and cellulose accumulation were closely associated with the minimum night temperature.