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1.
In the present work, thermogravimetric analysis of 17 organosolv lignin samples was carried out to determine their thermal stability and calculate the kinetic parameters of their pyrolysis. The thermal stability has been estimated by the measurement of the degradation temperature (Td), calculated according to the maximum reaction rate. In addition, degradation temperature at 10% of conversion (T10%) has been obtained in order to compare the initial stability of the samples with Td for all samples. The values of Td are comprised between 262 and 389 °C and the average value is 340 °C. The range for T10% is 251–320 °C and the average value is 270 °C. The ashes content of the samples has been analyzed and all the residues presented values lower than 4 wt%. Kinetic parameters of lignin pyrolysis were calculated by Borchardt–Daniels’ method assuming nth order reaction. The activation energy values obtained are comprised between 17.9 and 42.5 kJ/mol and the average value is 28.1 kJ/mol. These results are in agreement with the bibliography.  相似文献   

2.
Steam explosion of corn stalk in the presence of 3% sulphuric acid at 200 °C for 5 min gave the highest recovery of lignin. Lignin has Mw = 2640 and Mz = 93,994. In the UV spectrum absorptions at λ = 231 and 280 nm were recorded. 1H NMR spectrum of lignin showed signals attributable to cinnamaldehyde units, guaiacyl units, and syringyl units. Syringyl and guaiacyl units are in 1:1 ratio. 13C NMR spectrum showed signals for guaiacyl, syringyl, and p-hydroxyphenyl units. The spectrum showed a prevalence of guaiacyl units. The 13C NMR spectrum is in agreement with the presence of cinnamic units. The same characterization was performed on lignin from pine. The irradiation of lignin from pine from steam explosion process in the presence of oxygen, in conditions described for the formation of superoxide ion, for different irradiation time was followed isolating the lignin and determining the average molecular weight. The experiments showed that, until 8 h irradiation, Mn decreases, while Mw and Mz increases. After 8 h irradiation an inverse behaviour was observed, with an increase of Mn and a decrease of Mw and Mz. These results are in agreement with an initial polymerization process followed by a photoinduced degradation. Ozonization was carried out in acetonitrile–methanol solution. The reaction showed a zero-order kinetics. After 50 min the average molecular weight of lignin is the half. The reaction mixture was analyzed by using GC–MS. Oxalic acid was determined.  相似文献   

3.
《Field Crops Research》2001,69(2):143-149
Grindelia chiloensis (Asteraceae) is a shrub native to Patagonia, Argentina, and can accumulate as much as 25% resin (on a dry weight basis) in leaves. The resin can be used in applications similar to those of pine resins. Reductions in available radiation are thought to decrease both the plant C:N ratio and resin production. The objective of this study was to assess the effect of light availability on the allocation of photoassimilates to biomass, resin (terpenes) and carbohydrates in G. chiloensis. To examine this, three radiation treatments were applied to field grown plants: (i) 100% radiation (full-sun), (ii) 50% radiation and (iii) 25% photon flux density radiation. Changes in available radiation resulted in significant changes in above ground biomass accumulation, carbon based secondary metabolites (resin), non-structural carbohydrate (TNC) content, and relative growth rate (RGR). At low radiation levels, above ground biomass accumulation, RGR, resin, TNC content and CO2 assimilation rate were highly reduced (from 150 to 80 g per plant, from 16 to 7%, and from 30.2 to 8.6 g per plant, for biomass, resin content, and resin production, respectively). The responses to low radiation found in G. chiloensis would limit productivity and the distribution of this species when grown under cultivation.  相似文献   

4.
《Field Crops Research》2001,69(3):227-236
Grindelia chiloensis (Corn.) Cabr. is a shrub native to Patagonia, Argentina and can accumulate as much as 25% resin in its leaves, with net primary productivity between 90 and 170 g per year per plant when growing in native stands. Under cultivation, 67.4 g of resin per plant have been produced (about 2.24 Mg ha−1). The objective of this study was to assess the effect of irrigation regime on biomass and resin production on G. chiloensis. In order to achieve this objective, four irrigation treatments were performed during 1996–1997 and 1997–1998: (i) weekly irrigation (7d), (ii) irrigation at 20-day intervals (20d), (iii) irrigation at 40-day intervals (40d), (iv) non-irrigated (N-I). It was found that the intermittent water supply at 40d was sufficient to promote canopy development, and increase water use efficiency (WUE) and resin production per plant (RP) with highest resin production (approximately 5.12 Mg ha−1 in 1997). In order to achieve high levels of RP, above ground biomass was maximized at the expense of a reduction in WUE. A concomitant increase in WUE (at the leaf level; WUEL) and leaf resin content with water stress and time was found. This result supports the hypothesis that epicuticular resin could influence water transpiration (E), as it represents an additional barrier to gas diffusion from the epidermis and through the stomatal pores.  相似文献   

5.
The capitula of Cynara cardunculus contain hairs and pappi representing 7% of the total plant biomass. These low density biomass components could be mechanically separated without apparent losses using a whole-plant processing prototype. Hairs and pappi are filamentous structures made up of longitudinally aligned fibre cells, without intercellular voids or pitting, with the following dimensions regarding length, width and wall thickness: 1.35 mm, 19.8, and 4.8 μm for hairs and 1.78 mm, 10.4, and 2.9 μm for pappi. Chemically hairs and pappi have low content of ash (1.9% and 1.1%, respectively), extractives (5.4% and 6.0%) and lignin (10.6% and 17.8%), and high content of holocellulose (77.5% and 72.8%) and α-cellulose (55.2% and 46.8%).Pulps could be produced using a conventional kraft process with high yields and low residual lignin, e.g. 63% at Kappa 7 for hairs and 48% at Kappa 11 for pappi, low coarseness values (0.04 and 0.03 mg m?1) and adequate pulp properties for paper (40 and 42 N mg?1 tensile index; 3.6 and 3.4 kPa m2 g?1 burst index in unrefined pulps of hairs and pappi, respectively). The results also indicated that there is scope for improving pulp quality by optimising pulping conditions to this type of new raw materials. The differences between hairs and pappi may also be further exploited namely the lower lignin content of hairs and the higher slenderness and wall thickness of pappi fibres.The utilization of hairs and pappi may strengthen the differentiated use of biomass fractions of the Cynara plant and its potential as a bioenergy crop.  相似文献   

6.
Dewaxed wheat straw was treated with acetic acid–H2O (65/35, v/v), acetic acid–H2O (80/20, v/v), acetic acid–H2O (90/10, v/v), formic acid–acetic acid–H2O (20/60/20, v/v/v), formic acid–acetic acid–H2O (30/60/10, v/v/v), methanol–H2O (60/40, v/v) and ethanol–H2O (60/40, v/v) using 0.1% HCl as a catalyst at 85 °C for 4 h, in which 78.2, 80.0, 88.2, 89.4, 94.1, 23.5 and 37.4% of the original lignin, and 42.4, 58.7, 70.0, 65.1, 76.5, 14.2 and 22.2% of the original hemicelluloses was released, respectively. Lignins obtained were characterized by their content of hemicelluloses, composition of phenolic acids and aldehydes, molecular weight, thermal stability and by UV, Fourier transform infrared (FT-IR), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The results showed that aqueous organic acid was more effective than aqueous organic alcohol for extensive delignification and selective fractionation of cellulose, lignin and hemicelluloses from the straw. In particular, the addition of formic acid gave a significant effect on the dissolution of lignin. All the acid-insoluble lignin fractions contained small amounts of contaminated hemicelluloses as shown by their content of neutral sugars, 0.9–4.3%, and had weight-average molecular weight between 3960 and 4340 g mol−1. An increase in concentration of acetic acid or formic acid in organosolv resulted in an increment in release of guaiacyl units and in lignin condensation. However, the lignin preparations released during the treatment with aqueous organic alcohol without organic acid contained almost equal amounts of non-condensed guaiacyl and syringyl units with fewer p-hydroxyphenyl units. The β-O-4 ether bonds together with β-β, β-5 and 5-5′ carbon–carbon linkages were identified to be present in lignin substructures.  相似文献   

7.
Aligned epoxy-matrix composites were made from hemp fibres defibrated with the fungi Phlebia radiata Cel 26 and Ceriporiopsis subvermispora previously used for biopulping of wood. The fibres produced by cultivation of P. radiata Cel 26 were more cellulose rich (78%, w/w) than water-retted hemp due to more degradation of pectin and lignin. The defibrated hemp fibres had higher fibre stiffness (88–94 GPa) than the hemp yarn (60 GPa), which the fibre twisting in hemp yarn might explain. Even though mild processing was applied, the obtained fibre strength (643 MPa) was similar to the strength of traditionally produced hemp yarn (677 MPa). The fibre strength and stiffness properties are derived from composite data using the rule of mixtures model. The fibre tensile strength increased linearly with cellulose content to 850 MPa for pure cellulose. The fibre stiffness increased also versus the cellulose content and cellulose crystallinity and reached a value of 125 GPa for pure crystalline cellulose.  相似文献   

8.
The magnitude of relationships among different traits is important in plant breeding programs to identify the best selection criteria and improve the efficiency of selection. This study was conducted to determine relationships between seed yield and seed oil content with other important agronomic traits among 36 diverse accessions of Vernonia (Vernonia galamensis variety ethiopica), a potentially novel industrial oilseed crop. Field evaluations were conducted during 2005, 2006 and 2007 at the Limpopo Province in South Africa using a partially balanced lattice design. Simple correlation and path analysis were performed to identify the best selection criteria for increased seed yield and seed oil content. Simple correlation and path analyses revealed that the formation of productive primary heads strongly associated with increased seed yield (rg = 0.81, p < 0.001). Furthermore, path analysis indicated selection for increased number of primary heads would bring about simultaneous and favorable change towards reduced days to maturity and shorter plant height. Further associational study of traits with seed oil content showed a significant (p < 0.05) correlation between oil content with 1000 seed weight (rg = 0.4). The path analysis, however, exposed seed yield followed by 1000 seed weight with significant direct effect on seed oil content. The study demonstrated that selection for increased number of productive primary heads is the principal selection criterion to improve seed yield. Whereas selection for 1000 seed weight and increased seed yield serve as major selection criteria to achieve increased oil content in V. galemanesis.  相似文献   

9.
Lignin has long laboured under the label of “waste material”. However, as part of the thematic network EUROLIGNIN, a survey and desk study was undertaken to assess the changes and patterns in the utilisation of lignin with respect to materials applications. This showed that over the last 10–15 years there has been an explosion of research into, and commercialisation of, lignin-based products and processes which add significant value to a material that was previously, and continues to be, used as a low-value fuel for pulping boilers. The innate chemistry of lignin, a phenolic heteropolymer, has allowed it to make inroads into the high value polymer industries whilst continuing to act as feedstock material for the binder industries. Indeed the replacement of phenolics by lignin in resins systems is economically attractive with the phenolic resins market utilising approximately 2.52 M tonnes in 2001. Currently lignin, predominantly as lignosulphates, is used as a binding and dispersing agent in different industries with approximately 1 M tonnes (on a 100% solids basis) used annually, for example, in concrete admixtures. These and other applications will be discussed and expanded upon here with emphasis on both the economics of the markets and what is still required for lignin to mature as a valuable resource in its own right.  相似文献   

10.
The compositions of essential oils of 19 accessions belonging to six different Achillea species, transferred from the natural habitats in 10 provinces of Iran to the field conditions, were assessed. The relationship between the leaf areas of selected accessions with their essential oil content was also investigated. Essential oil yield of dried plants obtained by hydro-distillation ranged from 0.1 to 2.7% in leaves. Results indicated a significant variation in oil composition among and within species. Total of 94 compounds were identified in 19 accessions belonging to the six species of A. millefolium, A. filipendulina, A. tenuifolia, A. santolina, A. biebersteinii and A. eriophora. The major constituents of the leaves in the tested genotypes were determined as germacrene-D, bicyclogermacrene, camphor, borneol, 1,8-cineole, spathulenol and bornyl acetate. According to the major compounds, four chemotypes were defined as: (I) spathulenol (1.64–34.31%) + camphor (0.2–15.61%) (7 accessions); (II1) germacrene-D (18.78–23.93%) + borneol (7.93–8.26%) + bornyl acetate (11.56–14.66%) (5 accessions); (II2) germacrene-D (13.28–36.28%) + bicyclogermacrene (5.93–8.4%) + 1,8-cineole (15.26–19.41%) + camphor (14.95–23.32%) (2 accessions); (III) borneol + camphor (52.04–63.27) (2 accessions); (IV) germacrene-D (45.86–69.64%) (3 accessions). The relationships of chemotypes with soil type and climatic conditions of collected regions were assessed, as probable reasons of high variations in essential oil components, and discussed.  相似文献   

11.
Miscanthus × giganteus is one of the most promising biomass crops for non-food utilisation. Taking into account its area of origin (Far East), its temperature and rainfall requirements are not well satisfied in Mediterranean climate. For this purpose, a research was carried out with the aim of studying the adaptation of the species to the Mediterranean environment, and at analysing its ecophysiological and productive response to different soil water and nitrogen conditions. A split plot experimental design with three levels of irrigation (I1, I2 and I3 at 25%, 50% and 100% of maximum evapotranspiration (ETm), respectively) and three levels of nitrogen fertilisation (0 kg ha−1: N0, 60 kg ha−1: N1 and 120 kg ha−1: N2 of nitrogen) were studied. The crop showed a high yield potential under well-watered conditions (up to 27 t ha−1 of dry matter). M. × giganteus, in Mediterranean environment showed a high yield potential even in very limited water availability conditions (more than 14 t ha−1 with a 25% ETm restoration). A responsiveness to nitrogen supply, with great yield increases when water was not limiting, was exhibited. Water use efficiency (WUE) achieved the highest values in limited soil water availability (between 4.51 and 4.83 g l−1), whilst in non-limiting water conditions it decreased down to 2.56 and 3.49 g l−1 (in the second and third year of experiment, respectively). Nitrogen use efficiency (NUE) decreased with the increase of water distributed (from 190.5 g g−1 of I0 to 173.2 g g−1 of I2); in relation to N fertilisation it did not change between the N fertilised treatments (N1 and N2), being much higher in the unfertilised control (177.1 g g−1). Radiation use efficiency (NUE) progressively declined with the reduction of the N fertiliser level (1.05, 0.96 and 0.86 g d.m. MJ−1, in 1994, and 0.92, 0.91 and 0.69 g d.m. MJ−1, in 1995, for N2, N1 and N0, respectively).  相似文献   

12.
Using a face-centred composite experimental design with three central point replicates, we investigated the effects of cooking time (60–180 min), acetic acid concentration (60–95% of liquor weight) and HCl concentration (0.05–0.15% of liquor weight) on the yield, residual Klason lignin content and total polysaccharide content of pulps obtained from Miscanthus sinensis bark by the acetosolv process. Response surfaces fitted satisfactorily to the experimental results showed the most influential of the independent variables to be acetic acid concentration; increasing acetic acid concentration reduced yield and lignin content, and increased total polysaccharide content (except at the highest concentrations of the acids). The response surface for lignin content was used to design a Box–Wilson steepest-descent optimisation procedure to determine the conditions minimising pulp lignin content; the minimum achieved, 0.5%, was obtained using a cooking time of 147 min, an acetic acid concentration of 93.25% and an HCl concentration of 0.122%, under which conditions pulp yield was 52.6%.  相似文献   

13.
《Field Crops Research》2001,69(3):259-266
Water-use efficiency (WUEDM) is directly related to radiation-use efficiency (RUE) and inversely related to crop conductance (gc). We propose that reduced WUEDM caused by shortage of nitrogen results from a reduction in RUE proportionally greater than the fall in conductance. This hypothesis was tested in irrigated wheat crops grown with contrasting nitrogen supply; treatments were 0, 80 and 120 kg N ha−1 in 1998 and 0, 80, 120 and 160 kg N ha−1 in 1999. We measured shoot dry matter, yield, intercepted solar radiation and soil water balance components. From these measurements, we derived actual evapotranspiration (ET), soil evaporation and transpiration, WUEDM (slope of the regression between dry matter and ET), WUEY (ratio between grain yield and ET), RUE (slope of the regression between dry matter and intercepted radiation), and gc (slope of the regression between transpiration and intercepted radiation). Yield increased from 2.3 in unfertilised to an average 4.7 t ha−1 in fertilised crops, seasonal ET from 311 to 387 mm, WUEDM from 23 to 37 kg ha−1 mm−1, WUEY from 7.6 to 12.4 kg ha−1 mm−1, RUE from 0.85 to 1.07 g MJ−1, while the fraction of ET accounted for soil evaporation decreased from 0.20 to 0.11. In agreement with our hypothesis, RUE accounted for 60% of the variation in WUEDM, whereas crop conductance was largely unaffected by nitrogen supply. A greater fraction of evapotranspiration lost as soil evaporation also contributed to the lower WUEDM of unfertilised crops.  相似文献   

14.
Reduced plant biomass and increased plant-to-plant variability are expected responses to crowding in monocultures, but the underlying processes that control the onset of interplant interference and the establishment of hierarchies among plants within a stand are poorly understood. We tested the hypothesis that early determined plant types (i.e. dominant and dominated individuals) are the cause of the large variability in final kernel number per plant (KNP) usually observed at low values of plant growth rate (PGR) around silking in maize (Zea mays L.). Two hybrids (DK696 and Exp980) of contrasting response to crowding were cropped at different stand densities (6, 9 and 12 plants m−2), row spacings (0.35 and 0.70 m), and water regimes (rainfed and irrigated) during 1999/2000 and 2001/2002 in Argentina. The onset of interplant competition started very early during the cycle, and significant differences (P<0.05) in estimated plant biomass between stand densities were detected as soon as V4–6 (DK696) and V6–7 (Exp980). Plant population and row spacing treatments did not modify the onset of the hierarchical growth among plants, but did affect (P<0.02–0.08) the dynamic of the process. For both hybrids, the rate of change in relative growth between plant types was larger at 9 and 12 plants m−2 (ca. 0.12 g/g per 100 °C day) than at 6 plants m−2 (ca. 0.07 g/g per 100 °C day). For all treatments, the largest difference in estimated shoot biomass between plant types took place between 350 (V7) and 750 °C day (V13) from sowing, and remained constant from V13 onwards. Dominant plants always had more kernels per plant (P<0.05) than the dominated ones, but differences between plant types in PGR around silking were significant (P<0.05) only at 12 plants m−2. Our research confirmed the significant (P<0.01) curvilinear response of KNP to PGR around silking, but also determined a differential response between plant types: the mean of residual values were significantly (P<0.01) larger for dominant than for dominated individuals. Estimated ear biomass at the onset of active kernel growth (R3) reflected the variation in KNP (r2≥0.62), and was significantly (P<0.01) related to estimated plant biomass at the start of active ear growth (ca. V13). This response suggested that the physiological state of each plant at the beginning of the critical period had conditioned its reproductive fate. This early effect of plant type on final KNP seemed to be exerted through current assimilate partitioning during the critical period.  相似文献   

15.
The perennial C4 grass Miscanthus has been proposed as a biomass energy crop in Europe. Effects of crop age, irrigation and nitrogen fertilization on biomass and energy yields and N content of Miscanthus were investigated and the energy costs of production determined. After an establishment period of 1 year, cultivation of Miscanthus resulted in a dry matter production of over 37 t ha−1 year−1 over a period of 4 years. Irrigation and nitrogen level greatly affected Miscanthus biomass yield. In absence of N fertilization, irrigation did not modify biomass yield and the effect of irrigation increased with the increase in N level. The average N response ranged from 37 to 50 kg biomass kg−1 N applied. Because the calorific value of Miscanthus biomass (16.5 MJ kg−1) was not affected by irrigation and N fertilization, energy production depended exclusively on biomass yield. Maximum energy yield was 564 GJ ha−1 year−1. Without N supply and irrigation, energy yield was 291 GJ h−1. Net energy yield, calculated as the difference between energy output and input, but without inclusion of drying costs, was 543 GJ ha−1 with N fertilization and irrigation and 284 GJ ha−1 without; the ratios of energy output to input in crop production were 22 and 47, respectively.  相似文献   

16.
Structure and health effects of inulin-type fructans have been extensively studied, while less is known about the properties of the graminan-type fructans in wheat. Arabinoxylan (AX) is another important indigestible component in cereal grains, which may have beneficial health effects. In this study, the fructan content in milling fractions of two wheat cultivars was determined and related to ash, dietary fibre and AX contents. The molecular weight distribution of the fructans was analysed with HPAEC-PAD and MALDI-TOF MS using 1H NMR and enzymatic hydrolysis for identification of fructans. The fructan content (g/100 g) ranged from 1.5 ± 0.2 in flour to 3.6 ± 0.5 in shorts and 3.7 ± 0.3 in bran. A correlation was found between fructan content and dietary fibre content (r = 0.93, P < 0.001), but with a smaller variation in fructan content between inner and outer parts of the grain. About 50% of the dietary fibre consisted of AX in all fractions. The fructans were found to have a DP of up to 19 with a similar molecular weight distribution in the different fractions.  相似文献   

17.
Guayule (Parthenium argentatum Gray) is a source of high quality rubber and low-allergenic latex as well as resin for use as a wood preservative. Demand for high value latex products has increased with the advent of deadly diseases such as AIDS. The objective of this study was to evaluate the performance of six improved guayule lines (AZ-1 to AZ-6) in south-east Queensland: released jointly by the Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA) and The University of Arizona. Trials were conducted at two sites, Chinchilla and Gatton. Overall performance of improved lines for plant growth and yield of dry matter, rubber and resin was better at both Gatton and Chinchilla than the standard check lines (N 565 and 11591). AZ-1 and AZ-2 maintained the best combinations of desirable traits, including plant uniformity, early vigorous growth, increased dry matter, and increased rubber and resin yields. Of these two, AZ-2 had more uniform plant growth and has commercial potential for Queensland production areas. In the summer harvest at Gatton, 32-month-old AZ-1 and AZ-2 produced rubber yields of 789 kg/ha and 771 kg/ha, respectively, while controls, N 565 and 11591 produced 675 kg/ha and 618 kg/ha, respectively. At Chinchilla, at 33 months, spring harvested AZ-1 and AZ-2 produced rubber yields of 717 kg/ha and 787 kg/ha; these yields were significantly higher than N 565 and 11591 which produced 385 kg/ha and 380 kg/ha, respectively. Thus, rubber yields of AZ-1 and AZ-2 were consistently high across sites. AZ-1 and AZ-2 produced resin yields of 1158 kg/ha and 1115 kg/ha at Gatton and 1318 kg/ha and 1476 kg/ha at Chinchilla. This compared with a mean of 612 kg/ha and 352 kg/ha for the standard check lines at Gatton and Chinchilla. Thus resin yields of AZ-1 and AZ-2 were consistently high across sites. Rubber content appeared to be influenced by time of harvest although this effect is compounded with plant age. At Gatton, in spring, 17-month-old plants produced a mean rubber content of 7.7% (all lines), while, in summer, when the plants were 32-month-olds, rubber content dropped to 6.4%. At Chinchilla, 33-month-old plants harvested in spring produced a mean rubber content of 7.4%, similar to the spring value at Gatton. By contrast, resin content appeared to be little affected by season.  相似文献   

18.
Rice husk is a by-product of rice milling process, and a great resource as a raw biomass material for manufacturing value-added composite products. One of the potential applications is to use rice husk as filler for manufacturing gypsum–rice husk boards for wall and ceiling materials for construction. We investigated the effect of rice husk, addition on selected physico-mechanical properties, total volatile organic compound (TVOC), and incombustibility, on the gypsum board. With increasing rice husk contents, water and moisture absorption was decreased. Because of the replacement of pore between gypsum particles by rice husk, the moisture absorption was decreased as rice husk adding contents. By rice husk adding, MOR of the gypsum–rice husk boards were increased up to 9.8 MPa at 30 wt%. However, MOR was decreased more than 40 wt% of adding contents. The modulus of elasticity (MOE) showed similar behavior with MOR. However, internal bonding strength (IB) was slightly increased as rice husk adding contents up to 20 wt%, 0.5 MPa and decreased over 20 wt%. The incombustibility of the gypsum–rice husk boards decreased on increasing the rice husk adding content. However, up to 30 wt% of rice husk adding contents board samples was of incombustibility first class. Gypsum particle can be replaced up to 30 wt% by rice husk with incombustibility first class for housing materials. In all cases, TVOC emission factor and formaldehyde emission remained under the ‘Excellent’ grade as defined by Korean Air Clean Association (KACA).  相似文献   

19.
《Field Crops Research》2005,92(1):61-74
One of the main sources of considerable amounts of chloride to soils is irrigation water. The responses of tobacco (Nicotiana tabacum L.) to chloride are varied and inconsistent depending on the tobacco type, variety and methods of fertilization, cultivation and harvesting used. In this work, the impact of the interaction between four chloride levels (10, 20, 40, 80 mg L−1) in irrigation water and three nitrogen fertilizer forms (NO3–N 100%, NH4–N 100% and NO3–N 50%:NH4–N 50%) on growth, agronomic and chemical characteristics of Virginia tobacco was evaluated over 2 years (1999, 2000) in an outdoor pot experiment. The results showed that the adverse influence of chloride in irrigation water on plant height and number of leaves per plant was already substantial above 40 mg L−1, within 30 days after transplanting. In this period, visual toxicity symptoms of chloride appeared on the lower leaves of plants treated with ammonium nitrogen. In addition, the effect of chloride on flowering time, chlorophyll content of leaves, aboveground fresh weight of plant, total cured product yield and chemical characteristics, depended on the form of nitrogen, with nitrate nitrogen restricting the detrimental effects of chloride in irrigation water up to 40 mg L−1. The reduced yield of cured product at 80 mg L−1 was the result of the adverse effects of chloride on the leaves of the middle and upper stalk position. Leaf chloride concentration was highest in the upper leaves and increased linearly with the increase of chloride level in irrigation water at each leaf position on the stalk and this increase was more rapid as ammonium nitrogen percentage was increased. Chloride increased the concentration of reducing sugars in cured leaves at each leaf position, in all nitrogen forms and nicotine mainly in plants treated with nitrate nitrogen. The changes in total nitrogen and ash content are considered as minimal. We conclude that the optimum chloride level in irrigation water is below 20 mg L−1, whereas the level of 40 mg L−1 in combination with nitrate nitrogen fertilizers can be considered as the upper threshold to avoid adverse effects on Virginia tobacco.  相似文献   

20.
Moringa oleifera Lam. (M. pterygosperma Gaertn [Moringaceae]) is a fast-growing small tree native to the sub-Himalayan tracts of Northern India. The recognition that moringa oil has value in cosmetics has increased interest in cultivating it for seed-oil. The experimental trials were conducted in a semi-commercial moringa plantation in the subtropical northwestern region of Argentina, considering the similar climate conditions to the plant native region. Pods per tree, seeds per pod, weight of seed per pod, kernel weight, kernels oil content and fatty acid composition of PKM-1 and African cultivars were determined. One individual, E4-9, a PKM-1 plant, had significantly (P < 0.05) higher production than all other plants. In addition, this individual was the highest extrapolated oil producer in both 2003 and 2004, with 595 and 564 kg ha?1, respectively (ave. 580 kg ha?1). Seed weight (200-seed wt.) was significantly greater in 2003 than 2004; no other traits studied showed significant differences between years. Both cultivars produced-oil with practically identical fatty acid composition, and the monounsaturated ω-9 oleic fatty acid accounted for more than 70% of the total for both cultivars. The polyunsaturated ω-6 linoleic fatty acid content of the African cultivar was slightly, but significantly (P < 0.05), higher than that of PKM-1.  相似文献   

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