Organic matter chemistry and dynamics in clear-cut and unmanaged hardwood forest ecosystems

Forest harvesting alters the organic matter cycle by changing litter inputs and the decomposition regime. We hypothesized that these changes would result in differences in organic matter chemistry between clear-cut and uncut watershed ecosystems. We studied the chemistry of soil organic matter (SOM), and dissolved organic carbon (DOC) in soil solutions and stream samples in clear-cut and uncut sites at the Hubbard Brook Experimental Forest in New Hampshire using DOC fractionation techniques and solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy.Alkyl-C (aliphatic compounds) and O-alkyl-C (carbohydrates) were the largest C fractions in soil and dissolved organic matter at Hubbard Brook. Alkyl-C ranged from 29–48% of soil C, 25–42% of soil solution C, and 22–42% of streamwater DOC. Carbohydrates comprised 32–49%, 36–43%, and 29–60% of C in soils, solutions, and streamwater, respectively. In both soils and soil solutions, the carbohydrate fraction decreased with increasing soil depth, while the aromaticity of organic matter increased with depth. There were no significant differences in the structural chemistry of SOM between clear-cut and uncut watersheds.The aromatic-C fractions in soil solutions at the clear-cut site ranged from 12–16%, approximately 40% greater than at the uncut site (8.5–11%). Thus, clear-cutting has resulted in the leaching of more highly decomposed organic matter, and depletion of more aliphatic compounds in the soluble organic pool. Because DOC fluxes are small compared to the SOM pool, large differences in soil solution chemistry do not substantially alter the overall composition of SOM. While the organic chemistry of stream DOC varied greatly among 3 sampling dates, there were no obvious clear-cutting effects. Thus, temporal variations in flowpaths and/or in-stream processes appear to be more important than disturbance in regulating the organic carbon chemistry of these streams.     

Uptake of 5 9Fe from soluble 5 9Fe-humate complexes by cucumber and barley plants

The capability of cucumber (Cucumis sativus L., cv. Serpente cinese), a Strategy I plant and barley (Hordeum vulgaris L., cv. Europa), a Strategy II plant to use Fe complexed by a water-soluble humic fraction (WEHS) extracted from a peat, was studied. Uptake of ⁵⁹Fe from ⁵⁹Fe-WEHS by cucumber plants was higher at pH 6.0 than at pH 7.5. Roots of intact cucumber plants were able to reduce the Fe^III-WEHS complex either at pH 6.0 or 7.5, rates being higher in the assay medium buffered at pH 6.0. After supply of ⁵⁹Fe-WEHS, a large pool of root extraplasmatic ⁵⁹Fe was formed, which could be used to a large extent by Fe-deficient plants, particularly under acidic conditions. Uptake of ⁵⁹Fe from ⁵⁹Fe-WEHS by Fe-sufficient and Fe-deficient barley plants was examined during periods of high (morning) and low (evening) PS release. Uptake paralleled the diurnal rhythm of PS release. Furthermore, ⁵⁹Fe uptake was strongly enhanced by addition of PS to the uptake solution in both Fe-sufficient and Fe-deficient plants. High amount of root extraplasmatic ⁵⁹Fe was formed upon supply of Fe-WEHS, particularly in the evening experiment. Fe-deficient barley plants were able to utilize Fe from the root extraplasmatic pool, conceivably as a result of high rates of PS release. The results of the present work together with previous observations indicate that cucumber plants (Strategy I) utilize Fe complexed to WEHS, presumably via reduction of Fe^III-WEHS by the plasma membrane-bound reductase, while barley plants (Strategy II) use an indirect mechanism involving ligand exchange between WEHS and PS.     

Fe enriched biosolids as fertilizers for orange and peach trees grown in field conditions

Iron enriched biosolids (FEB) from water treatment facilities are being used as an alternative to synthetic chelates in order to improve Fe uptake. The impact of this type of products on iron nutrition is not fully understood. Plant response depends on FEB composition, soil and climatic conditions and crop response. In order to study the effectiveness of FEB as fertilisers, two field experiments have been carried out. Two different commercial formulations of FEB (unmodified u-FEB and modified m-FEB) produced as a by-product of a drinking water treatment facility in Tampa (Florida, USA) were used. An orange tree (Citrus sinensis, cv. Navelina) and a peach tree (Prunus persica cv. Sudanell) field experiments took place in different locations in Spain. Macro and micronutrients were evaluated to assess mineral status of orange and peach leaf samples. Yield and fruit size were also determined. Despite the large amount of Fe bound by the organic matter on FEB, these products were less effective than synthetic chelates to improve iron uptake. No differences were found in orange yield or size. Results show that the ferric treatments improve fruit calibre, but not yield in peaches.     

Hormonal factors controlling the initiation and development of lateral roots

As the first part of a comprehensive study of the hormonal control of lateral root initiation and development, the effect of surgical treatments such as removal of the root tip, one or more cotyledons, the young epicotyl, or combination of these treatments, on the induction and emergence of lateral roots on the primary root of pea seedlings has been examined. Results show that removal of the root tip leads to a rapid but transitory increase in the number of lateral primordia, the largest number arising in the most apical segment of decapitated roots suggesting the accumulation of acropetally moving promoter substances in this region. The cotyledons appear to be the main source of promoter substances for both the induction and emergence of lateral roots, although one or more promoters also appear to be produced in the epicotyl. The data further indicate that the root tip is possibly the source of a substance which moves basipetally and interacts with acropetally moving promoters to regulate the zone for lateral primordia initiation; the root tip also appears to be the source of a powerful inhibitor of lateral root emergence.     

Effects of the Addition of Humic Substances on Soil Protease Activities in Andosols in the Presence of Cadmium

Cadmium extraction, sorption, and immobilization seem to be the effective mechanisms in detoxification of Cd-contaminated soil. Humic substances present in soils may play an important role both in controlling the negative effects of pollution with Cd and in stabilizing soil enzymes. In this context, we have compared the effects of humic substances on soil protease activities in the presence and absence of Cd in forest and cultivated field soil samples. The samples were taken from surface soils of Andosols in a single upland area of the Kanto district in Japan. Humic substances extracted from the two soils showed differences in elemental composition, the degree of condensation of aromatic groups, and the proportions of major functional groups. Compared with the control soil samples, those with added humic substances showed a significant increase in protease activities, even in the presence of Cd (10 and 50 mg Cd kg^?1 soil). However, the addition of Cd decreased the protease activities, protein contents, and soil pH in both soil samples at each of the two levels of humic substance fortification (+5% and +10%). Moreover, protease activities showed significant negative correlation with exchangeable Cd, but adding humic substances did not lead to a reduction in either sample. Thus, although the addition of humic substances increased and stabilized protease activities, it did not lead to a clear reversal of enzyme inhibition by Cd. The obtained results indicate that in both soil samples the humic substances used in this study did not have sufficient affinity to adsorb Cd, and the impact on enzyme activities depends on the difference in chemical characteristics of the added organic matter, as suggested by the difference in enhancement of protease activities between forest and cultivated field soil samples.     

EPS and SMP dynamics at different heights of a submerged anaerobic membrane bioreactor (SAMBR)

Membrane bioreactors (MBR) technology for wastewater offers many advantages over conventional technologies such as high effluent quality, less footprint and others. The main disadvantage of membrane bioreactors (MBR) is related to membrane fouling, which is mainly caused by extracellular polymeric substance (EPS) and soluble microbial products (SMP). This research studied EPS and SMP dynamics at different heights of a submerged anaerobic membrane bioreactor (SAMBR). The SAMBR was operated under two organic loading rates (OLR) (0.79 and 1.56 kg/m³ d) and was fed with synthetic wastewater with glucose as the carbon source. The results showed percentages of chemical oxygen demand (COD) removal above 95% and the highest COD removal rates were observed at the bottom of the reactor (>83%) for both OLR. The EPS showed a stratification with highest quantities in the supernatant. For the SMP the highest concentration was in the bottom of SAMBR where utilization predominated associated products whereas in the SAMBR supernatant predominated biomass associated products. The OLR change led to a significant increase in SMP accumulation but not in EPS. These facts showed that EPS and SMP dynamic in the SAMBR seemed to be mainly influenced by biological activity, total suspended solids concentration and substrate composition.     

Effect of BCAA intake during endurance exercises on fatigue substances,muscle damage substances,and energy metabolism substances

The increase rate of utilization of branched-chain amino acids (BCAA) by muscle is reduced to its plasma concentration during prolonged exercise leading to glycogen. BCAA supplementation would reduce the serum activities of intramuscular enzymes associated with muscle damage. To examine the effects of BCAA administration on fatigue substances (serotonin, ammonia and lactate), muscle damage substances (CK and LDH) and energy metabolism substances (FFA and glucose) after endurance exercise. Subjects (n = 26, college-aged males) were randomly divided into an experimental (n = 13, EXP) and a placebo (n = 13, CON) group. Subjects both EXP and CON performed a bout of cycle training (70% VO₂max intensity) to exhaustion. Subject in the EXP were administrated BCAA (78ml/kg·w) prior to the bout of cycle exercise. Fatigue substances, muscle damage substances and energy metabolism substances were measured before ingesting BCAAs and placebos, 10 min before exercise, 30 min into exercise, immediately after exercise, and 30 min after exercise. Data were analyzed by two-way repeated measure ANCOVA, correlation and statistical significance was set at p < 0.05. The following results were obtained from this study; 1. In the change of fatigue substances : Serotonin in the EXP tended to decreased at the 10 min before exercise, 30 min into exercise, post exercise, and recovery 30 min. Serotonin in the CON was significantly greater than the EXP at the10 min before exercise and recovery 30. Ammonia in the EXP was increased at the 10 min before exercise, 30 min into exercise, and post exercise, but significantly decreased at the recovery 30min (p < 0.05). Ammonia in the CON was significantly lower than the EXP at the 10 min before exercise, 30 min into exercise, and post exercise (p < 0.05). Lactate in the EXP was significantly increased at the 30 min into exercise and significantly decreased at the post exercise and recovery 30 min. Lactate in the CON was significantly lower than the EXP at the post exercise (p < 0.05). 2. In the change of muscle damage substances : CK in the EXP was decreased at the 10 min before exercise and increased at the 30 min into exercise and then decreased at the post exercise and recovery 30 min. CK in the CON was greater than the EXP. LDH in the EXP was decreased at the 10 min before exercise and increased at the 30 min into exercise and then decreased at the post exercise and recovery 30 min. LDH in the CON was higher than the EXP. 3. In the change of energy metabolism substances :Glucose in the EXP tended to decrease at the 10 min before exercise, 30 min into exercise, post exercise and recovery 30 min. Glucose in the CON was significantly greater than the EXP at the recovery 30 min (p < .05). FFA in both EXP and CON was increased at the post exercise and recovery 30 min. % increase for FFA in the EXP was greater than the CON at the post exercise and recovery 30 min. 4. The relationship of the fatigue substances, muscle damage substances and energy metabolism substances after endurance exercise indicated strongly a positive relationship between LDH and ammonia and a negative relationship between LDH and FFA in the EXP. Also, there were a strong negative relationship between glucose and FFA and a positive relationship between glucose and serotonin in the EXP. There was a strong positive relationship between CK and LDH and a strong negative relationship between FFA and glucose in the CON. These results indicate that supplementary BCAA decreased serum concentrations of the intramuscular enzymes as CK and LDH following exhaustive exercise. This observation suggests that BCAA supplementation may reduce the muscle damage associated with endurance exercise.     

Biostimulant activity of humic-like substances from agro-industrial waste on Chlorella vulgaris and Scenedesmus quadricauda

The use of microalgae in a number of sectors, including biodiesel, feed and food production, is proving to be of great interest. An evaluation was made of the possible biostimulant effects on Chlorella vulgaris and Scenedesmus quadricauda of humic-like substances (HLs) extracted from agro-industrial wastes. These included digestate from the waste of an agro-livestock farm (D-HL), oil extraction residues from rape (B-HL, Brassica napus L.) and tomato residues (T-HL). The microalgal growth medium (BG11) was supplemented with HLs to evaluate their effect on biomass yield as well as carbohydrate, chlorophylls a and b, lipid and fatty acid contents. Our results showed that the HLs used in the test are effective biostimulants of C. vulgaris and S. quadricauda. The biostimulant effect seems to depend on the type of extract used for cultivating the microalgae, the concentration and the species treated. Among the extracts applied to the growth medium, D-HL and T-HL seem to have a significant effect on microalgal biomass and lipid production. Although B-HL showed no significant effect on the biomass and lipid content of C. vulgaris and S. quadricauda, its presence in the growth medium increased the saturated:unsaturated fatty acid ratio (SFA/UFA) and stimulated the sugar metabolism of the microalgae by increasing their carbohydrate and chlorophyll content.     

北虫草栽培残基中主要活性物质含量分析及评价

对北虫草栽培残基中蛋白质、虫草素等主要营养及活性物质含量分析,为其资源化合理利用研究提供参考。采用反相高效液相色谱法测定氨基酸含量,半微量凯氏定氮法测定粗蛋白,稀酸碱处理法测定粗纤维含量,旋光度法测量淀粉含量,电感耦合等离子体原子发射光谱法测定矿质元素钙及磷含量,苯酚硫酸法测定多糖的含量,高效液相色谱法测定虫草素。结果显示,北虫草栽培残基中主要营养成分氨基酸、粗蛋白、粗纤维、淀粉、含量检测分别为8. 17%、18. 4%、4. 9%、43. 1%;矿质元素钙及磷含量分别为0. 09%、0. 46%;主要活性成分虫草多糖含量可达4. 8%,与子座含量(5. 1%)相当;虫草素含量0. 318%,显著高于子座(0. 166%)中虫草素含量。结果表明,北虫草栽培残基中除富含蛋白质、氨基酸、淀粉等营养物质外,还含有虫草素、虫草多糖等北虫草特有的活性物质,具有较大营养价值。北虫草栽培残基综合利用资源化研究应用前景广阔。     

2种枸杞叶片对混合盐胁迫的生理响应

选取耐盐性不同的‘宁杞5号’和‘黑杞1号’一年实生苗为试验材料,进行渗透势分别为-0.47、-0.82和-1.18MPa的混合盐(NaCl+Na_2SO_4)胁迫处理,分析比较2种枸杞叶片生理指标的响应特征,以揭示2种枸杞适应盐胁迫的生理机制。结果表明:(1)随着渗透势降低,2种枸杞叶片生理指标响应趋势基本一致,叶绿素(Chl)和可溶性蛋白(SP)含量先升后降,相对电导率、丙二醛(MDA)和脯氨酸(Pro)、可溶性糖(SS)含量逐渐增加,但‘宁杞5号’的变化幅度大于‘黑杞1号’。(2)随着渗透势降低,2种枸杞叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性均增强,但-1.18 MPa混合盐溶液处理则抑制了‘宁杞5号’抗氧化酶活性。(3)随着盐胁迫处理时间的延长,2种枸杞叶片相对电导率、MDA含量、Pro含量、SS含量和CAT活性增加,但‘宁杞5号’的渗透调节物质积累量高于相应‘黑杞1号’;而2种枸杞Chl含量及SOD和POD活性在-1.18 MPa混合盐溶液处理下有所下降。研究表明,2种枸杞均可通过积累渗透调节物质和加强抗氧化酶系统来缓解盐胁迫对自身的伤害,‘宁杞5号’的渗透调节能力较强,而‘黑杞1号’具有更稳定的抗氧化酶系统,从而具有更强耐受盐胁迫的能力。