Hemicelluloses of Arundo donax at different stages of maturity

The hemicellulosic composition of the internodes of Arundo donax depends on the maturity of the tissue. The percentage of xylose in the total hemicellulose increases with increasing plant maturity. The main hemicellulose is an arabino-4-O-methyl glucurono xylan which is already present in the youngest tissues and has the same structural features regardless of the age of the tissues. The average D.P. of this polysaccharide increases from about 60 to 150 with maturation of the plant tissue.     

Estimating Arundo donax shoot biomass

We developed an equation for estimating Arundo donax shoot dry weight from shoot length. The equation, shoot dry weight (g) = 14.254 (standard error = ±0.275) × shoot height² (m), was as effective at explaining a high proportion of total variation in shoot dry weight (R² = 0.90) as more complicated equations containing additional morphometric parameters. Tested against two independent datasets, the equation provided accurate estimates of dry weight for shoots ranging from 0.3 to 7.06 m height (dataset 1, P < 0.0001, R² = 0.87, N = 29; dataset 2, P < 0.0001, R² = 0.82, N = 192). The equation provides aboveground biomass estimates from stem counts and heights more rapidly than harvest methods.     

Estimating Arundo donax ramet recruitment using degree-day based equations

Arundo donax is a tall perennial reed. Once established, it spreads by producing new shoots (ramets) from rhizomes. We performed two separate experiments to test the hypotheses that temperature (7, 8, 14, 16, or 20 °C) and combinations of temperature and nitrate concentration (0, 0.3, 0.6,1.2, 2.4, 3.6, 4.8, and 6.0 mg/l nitrate) regulated the initiation of ramet production. No ramets emerged from rhizome sections at 7 or 8 °C, but ramets emerged at 14, 16, and 20 °C. Neither time to ramet emergence nor the number of ramets that emerged was influenced by nitrate level in the watering solution. We used the above results in combination with ramet emergence data from plants grown outdoors at Davis, California to develop degree-day equations for three separate ramet cohorts. When compared to ramet emergence from different plants in different years, there was very good agreement between predicted and actual ramet emergence indicating that these equations provide a realistic representation of processes involved in ramet emergence. This is an important step in developing integrated management plans for this species.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Variation in Arundo donax stem and leaf strength: Implications for herbivory

We determined leaf and stem strength for Arundo donax from plants grown in different geographic areas and at different times within their growing cycle. Mean leaf strength for plants collected within California was 1.72 Newtons (N) and ranged from 0.36 to 6.32 N, based on 1170 individual determinations. For leaves collected from 30 plants within four states between July 11 and 20, 2007, mean leaf strength was 1.58 N based on 936 determinations. Values ranged from 0.24 to 4.90 N. Overall, leaf strength showed statistically significant changes depending on the sampling date, sampling location, type of leaf sampled, and position within the leaf where the measurement was taken. In general leaf strength was greater near the base of the leaf and decreased with distance away from the base; leaf strength changed as the growing season progressed; and first year leaves had leaf strength values about 25% greater than leaves produced on stems >1-year old. This represents two of the three age categories of leaves which may be present on giant reed at any one time. Stem strength and stem wall thickness were strongly correlated (Kendall's Tau b = 0.92, P < 0.0001, N = 26). Linear regression indicated that mean stem strength decreased by approximately 6.8% (95% confidence limits 5.8-7.7%) from one node to the successive node progressing from the stem base to the shoot tip. These results imply that the ability of biological control agents to damage A. donax leaves may not be the same across the locations this plant occurs or at all times during the growing season within a given location.     

Hydrothermal and thermal time models for the invasive grass, Arundo donax

Controlled laboratory and field experiments were performed to determine the developmental response to temperature and moisture of Arundo donax, a riparian invasive grass and potential bioenergy crop. A logistic function was parameterized and used to predict thermal times to sprouting and the nine-leaf stage. Consistent estimates of the base temperature (T_b) and base water potential (ψ_b) below which development ceases were obtained from various statistical and mathematical analyses. Estimates of T_b and ψ_b were 12.7 ± 1.7 °C and −1.56 ± 0.43 MPa, respectively, for the median fraction of sprouting rhizomes. Median hydrothermal time to sprouting was 124.1 MPa °Cd under laboratory conditions and median thermal times, or degree-day (°Cd), to sprouting and nine-leaf stage was estimated to be 94 and 129 °Cd under field conditions, respectively. A degree-day is defined as one day (24 h) spent one degree above T_b. Results demonstrated that thermal time alone is sufficient to accurately predict time to sprouting under field conditions. Further, there may be a fixed moisture threshold of about 6% volumetric water content above which sprouting rate was constant. This threshold corresponded very closely to the −1.5 MPa for ψ_b that was estimated under laboratory conditions for the soil typically infested by A. donax. This information is crucial for assessing risk of invasive spread for A. donax.     

Arundo donax L.: A non-food crop for bioenergy and bio-compound production

Arundo donax L., common name giant cane or giant reed, is a plant that grows spontaneously in different kinds of environments and that it is widespread in temperate and hot areas all over the world. Plant adaptability to different kinds of environment, soils and growing conditions, in combination with the high biomass production and the low input required for its cultivation, give to A. donax many advantages when compared to other energy crops. A. donax can be used in the production of biofuels/bioenergy not only by biological fermentation, i.e. biogas and bio-ethanol, but also, by direct biomass combustion. Both its industrial uses and the extraction of chemical compounds are largely proved, so that A. donax can be proposed as the feedstock to develop a bio-refinery.     

Molecular evidence for a single genetic clone of invasive Arundo donax in the United States

Arundo donax (giant reed) is an aggressive invasive weed of riparian habitats throughout the southern half of the United States from California to Maryland. Native to Asia, the species is believed to have been initially introduced into North America from the Mediterranean region although subsequent introductions were from multiple regions. To provide insight into the potential for biological control of A. donax, genetic variation in plants sampled from a wide geographical area in the United States was analyzed using Sequence Related Amplification Polymorphism (SRAP) and transposable element (TE)-based molecular markers. Invasive individuals from 15 states as well as four populations in southern France were genetically fingerprinted using 10 SRAP and 12 TE-based primer combinations. With the exception of simple mutations detected in four plants, A. donax exhibited a single multilocus DNA fingerprint indicating a single genetic clone. The genetic uniformity of invasive A. donax suggests that classical biological control of the species could be successful. A lack of genetic diversity in the invaded range simplifies identification of native source populations to search for natural enemies that could be used as biocontrol agents.     

Xylose production from giant reed (Arundo donax L.): Modeling and optimization of dilute acid hydrolysis

Statistical modeling and optimization of dilute sulfuric acid hydrolysis of potential energy crop giant reed (Arundo donax L.) has been performed using response surface methodology. Central composite rotatable design was applied to assess the effect of acid concentration, reaction time and temperature on efficiency and selectivity of xylan polysaccharide conversion to xylose. Second-order polynomial model was fitted to experimental data to find the optimum reaction conditions by multiple regression analysis. The monomeric xylose recovery ca. 94% (vs. 93% predicted) was achieved under optimized hydrolysis conditions (1.27% acid concentration, 141.6 °C and 36.4 min), confirming the high validity of the developed model. The low content of glucose (2.7%) and monosaccharide degradation products (0.9% furfural and 0.7% 5-hydroxymethylfurfural) provided a high quality xylose-rich subtract, ready for subsequent biochemical conversion to value-added products. The solid xylan-free residue was easily converted to fermentable sugars resulting in cellulose digestibility of 70% vs. 9% for untreated biomass.     

Hormones of young tassels of Zea mays

The ethyl acetate-soluble acids from an aqueous methanolic extract of young tassels from Zea mays plants were fractionated by treatment with PVP, then by chromatography on a column of celite-charcoal. Methylated and trimethylsilylated fractions were analysed by GC/MS and the following compounds were identified by comparison with reference spectra: GA₁₇, GA₁₉, GA₂₀, GA₄₄, GA₅₃, ABA, phaseic acid and dihydrophaseic acid. Evidence is also presented for the presence of metabolise C of ABA and of a 16,17-dihydro-17-hydroxy-derivative of GA₅₃. In addition, the presence of small amounts of GA₁, GA₈ and GA₂₉, was indicated from a derivatized fraction analysed by capillary GC/SICM.     

The flavonoids of phragmites australis flowers

The major flavonoid constituents of Phragmites australis flowers are the C-glycosylflavones swertiajaponin, isoswertiajaponin and two new O-glycosides, the 3′-O-gentiobioside and the 3′-O-glucoside of swertiajaponin. Two unusual flavonol glycosides, rhamnetin 3-O-rutinoside and rhamnetin 3-O-glucoside, were also characterized from the same tissue.     

tRNA species in the developing grain of triticum aestivum

The level of lysyl- and prolyl-tRNA in various stages of the maturing wheat grain was measured by the aminoacylation procedure. The levels of these tRNAs changed only slightly during the maturation period. Several species of lysyl- and prolyl-tRNA were obtained from different parts of the developing grain by fractionation on benzoylated-DEAE cellulose (BD-cellulose). The embryo contained three discrete species of prolyl and at least three species of lysyl isoacceptor tRNA throughout development, whilst the tRNA obtained from the endosperm gave more complicated elution profiles on chromatography on BD-cellulose. Small changes were noted in the levels of aminoacylation of individual isoacceptor tRNA species for lysine or proline during seed maturation. However, these were insufficient to account for the changing pattern of lysine and proline in the storage protein during the development of the endosperm.     

Degradation of [β-14C]hordenine in Hordeum vulgare plants

[β-¹⁴C]Hordenine is ultimately degraded by intact plants of Hordeum vulgare to C₆-C₁ intermediates that are incorporated into polymeric material.     

Benzoxazinones from Coix lachryma-jobi var. ma-yuen

The absolute configurations of 2-O-β-D-glucopyranosyl-7-methoxy-1,4(2H)-benzoxazin-3-one and three congeners isolated from Coix lachryma-jobi var. ma-yuen were determined by X-ray analysis and chemical correlation as the 2R type. ¹³C NMR spectra of all congeners and coixol were fully assigned.     

Amino acids in Hordeum distichon and Panicum miliaceum grown in sand culture

In comparison with barley, Proso millet was characterized by high levels of alanine and glutamic acid in the leaf free amino acid fraction. In both species, analyses of root amino acids and xylem exudates suggest the existence of specific mechanisms for the transfer of certain amino acids into the xylem vessels.     

Peroxidase isoenzymes of the Avena coleoptile

The bulk of the peroxidases of Avena coleoptile sections exist in soluble and salt-extractable, wall-associated fractions with lesser amounts in membranous and wall-bound fractions. In the presence of auxin the peroxidase levels remain nearly constant while in the absence of auxin the peroxidase of each fraction increases 2-to 6-fold in 22 hr. There are qualitative and quantitative changes in the isoenzyme patterns with time, but these changes are independent of auxin. It is concluded that the peroxidase changes are induced by isolation of the tissues from the coleoptile and are unrelated to the growth rate.     

Biosynthetic relationship of citral-trans and citral-cis in cymbopogon flexuosus (lemongrass)

Use of [¹⁴C,³H]-labelled precursors revealed that leaf blades of Cymbopogon flexuosus converted geraniol (3,7-dimethylocta-trans-2,6-diene-1-ol) into citral-trans with loss of pro-(1S) hydrogen whereas nerol lost the pro-(1R) hydrogen while being converted into citral-cis. Secondly, the citral-trans is converted into citral-cis and vice versa and there is no separate route for the biosynthesis of either of the two aldehyde isomers.     

Flavonol glucosyltransferase activity in Bronze embryos of Zea mays

The major UDPG: flavonol glucosyltransferase (UFGT) in maize is an enzyme of strict positional specificity known to be coded by the Bz locus. In bz mature endosperms, no UFGT can be detected. However, bz embryos possess a residual flavonol glucosyltransferase activity which is independent of Bz locus control. The products of this activity have been identified as the 3′-, 7- and 3-glucosides.     

Indole-3-acetyl-myo-inositol in kernels of Oryza sativa

IAA-myo-inositol was isolated from kernels of Oryza sativa and characterized by its chromatographic properties and its mass spectral fragmentation pattern. This is the first demonstration of the occurrence of a myo-inositol ester of IAA in a plant other than Zea mays.     

Terpenes of Podocarpus lambertius

Sitosterol and the following terpenic compounds have been isolated from the bark of Podocarpus lambertius: 3β-hydroxytotarol, 4β-carboxynortotarol, and macrophyllic and lambertic acids. The leaves yielded sitosterol, stigmastan-3β,5α-diol-6-one, isopimaric acid, phyllocladene, isophyllocladene, 8,9-abieten-15-ol and 17-isophyllocladenol.