Water adsorption properties of bamboo in the longitudinal direction

Differences in the water adsorption properties of moso bamboo (Phyllostachys pubescens) were examined by analyzing the isotherms. Hygroscopicity decreased from the bottom to the top of the culm, and this tendency was marked above about 80% relative humidity. Results of alkali extraction and the analysis of bundle sheath distribution revealed that the distribution of hygroscopic saccharides, for example, hemicelluloses and less-hygroscopic vascular bundles, affects the hygroscopicity, which varies depending on the position of the internode.     

Smith degradation,an efficient method for the preparation of cycloastragenol from astragaloside IV

Cycloastragenol (CA) is the genuine sapogenin of astragaloside IV (ASI). This study focuses on the preparation of CA from ASI. Five hydrolysis methods were compared including H₂SO₄ hydrolysis, HCl hydrolysis, two-phase acid hydrolysis, mild acid hydrolysis, and Smith degradation. Seven hydrolysis products were purified, and five of them were identified as new compounds. The results indicated that Smith degradation was the most effective approach to prepare CA. In contrast, mild acid hydrolysis produced CA at a low yield, accompanied with the artificial sapogenin astragenol. The other three acid hydrolysis methods mainly produced astragenol. Furthermore, the reaction conditions for Smith degradation were optimized as follows: ASI was dissolved in 60% MeOH–H₂O solution, oxidized with 5 equiv. NaIO₄ for 12 h, followed by reduction with 3 equiv. NaBH₄ for 4 h, and finally acidified with 1 M H₂SO₄ at pH 2 for 24 h. Under the optimal conditions, CA could be prepared from ASI at a yield of 84.4%.     

Pre-sowing treatments for improved germination and growth of two rare native species of Bangladesh

Pre-sowing treatments are expected to increase seed germination. This evaluates response to pre-sowing treatments and the growth performance of two native and rare tree species, Garuga pinnata Roxb. and Vitex glabrata R. Br. The hard seed coats were treated by rubbing with sand paper, nail clipping, and immersion in water and acid (H₂SO₄). Results indicate that G. pinnata showed a 90% germination rate and 30% germination energy when seed coats were nicked with a nail clipper. Rubbing with sand paper was the best pre-sowing treatment for V. glabrata, resulting a 80% germination rate and 30% germination energy. G. pinnata and V. glabrata seedlings from seeds soaked 24 h in water resulted in maximum heights and collar diameters. These were significantly higher (at p < 0.05) than those of other treatments. The results indicate that scarification or nicking of seeds may have some negative impacts on seedling growth. Therefore, it is difficult to recommend a pre-sowing treatment of seeds for achieving both maximum germination and good early seedling growth.     

Structural, histochemical and chemical characterization of normal, tension and opposite wood of Subabul (Leucaena leucocephala (lam.) De wit.)

Structure, histochemistry and chemical composition of tension (TW), opposite (OW) and normal wood (NW) of Leucaena leucocephala have been studied using histological, histochemical and biochemical methods. TW vessels are longer and have a larger diameter than NW vessels, and the rays are shorter and thinner. The G-layer replaced S3 and parts of S2 wall layers in TW fibres. TW further contained less lignin that also had a lower syringyl-to-guaiacyl ratio. The lignin was also more condensed. The content of α-cellulose was high in TW. TW contains hemicelluloses and pectins composed of more galactose, and less xylose, mannose, 4-O-methylglucuronic acid and galacturonic acid compared to that of OW. This study suggests that in the TW of Leucaena, the amount and composition of lignin, hemicelluloses and pectins differ considerably from that in OW and NW.     

Chemical characterization of Pinus halepensis sapwood and heartwood

ABSTRACT

This paper describes the chemical composition of sapwood (SW) and heartwood (HW) of Pinus halepensis Mill stem. Extractives were first isolated by accelerated solvent extraction and then analysed by gas chromatography-mass spectrometry (GC-MS). The cellulosic polysaccharide content present in the pre-extracted wood samples was determined with acid hydrolysis and GC. The hemicelluloses content was determined with acid methanolysis and GC. Free monomers were additionally analysed by GC. The amount of lignin was determined gravimetrically by the Klason lignin method and the acid-soluble lignin was determined by a UV method. Formic and acetic acids in wood were determined after alkaline hydrolysis and analysed by HP-SEC. It was found that lipophilic and hydrophilic extractives were more abundant in heartwood (1.6% and 2.5%) than in sapwood (1.1% and 1.8%). Celluloses content was higher in sapwood (42.5%) than in heartwood (39.7%), whereas lignin, hemicelluloses and sugar monomer contents were more abundant in heartwood (28.9%, 26.8% and 0.3%) than in sapwood (28.0%, 24.5% and 0.2%). The variation in acetic and formic acids and ash contents between sapwood (0.7%, 0.2% and 0.5%) and heartwood (0.6%, 0.1% and 0.4%) was small. The acetylation degrees were found to be slightly similar in sapwood (0.4) and heartwood (0.3).     

Seedling growth and water relations of three Cedrela species sourced from five provenances: response to simulated rainfall reductions

The effects of different simulated rainfall regimes on water relations, growth, and biomass production and allocation of five provenances of Cedrela fissilis, C. saltensis and C. balansae were assessed in a pot-grown seedling experiment in greenhouse under uncontrolled conditions. Four simulated rainfall regimes were applied: 600 mm year^?1 (severe water deficit), 800 mm year^?1 (mild water deficit), 1,000 mm year^?1 (mild wet), and 1,200 mm year^?1 (well-watered) used as control. Provenances were compared in terms of water relations (midday leaf water potential, Ψ _md and relative water content, RWC), growth (root, shoot and leaf length, neck diameter), growth rate (shoot- and neck growth rate, SGR and NGR), biomass production (root, shoot and leaf dry weight), and biomass allocation (root:shoot ratio, RSR). Multivariate analyses revealed that water relations differed significantly under all simulated rainfall treatments by means of several variables throughout time. Effects of species × treatment, and provenance nested within species × treatment interactions significantly were important. SGR and RSR also were important to explain differences in Ψ _md and RWC between treatments and provenances. Broadly C. balansae and C. saltensis provenances seem to display a better performance than C. fissilis provenances under severe water deficit only. However, despite differences between provenances, it was not possible to clearly separate them according to their origin, based on water relations and growth performance. Even though the results of this study performed on pot-grown seedlings are based on relatively few observations and require additional confirmation, they allow an opportunity for speculation on the factors that are related to intraspecific variations that are likely to occur during the growth of seedlings from different geographical sites in field condition.     

MALDI-TOF/MS analyses of decomposition behavior of beech xylan as treated by semi-flow hot-compressed water

Japanese beech (Fagus crenata) was treated with semi-flow hot-compressed water at various temperatures of 150–230 °C under 10 MPa. The obtained various products were then analyzed with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS). In a temperature range of 150 °C up to 210 °C, however, no hydrolyzed products were found, and at 210 °C/10 MPa, O-acetyl-4-O-methylglucuronoxylo-oligosaccharides (X _n Ac _m MG _i ) and O-acetyl-xylo-oligosaccharides (X _n Ac _m ) were obtained, indicating the first cleavage of native xylan β-1,4-glycosidic linkages followed by a cleavage of α-1,2-glycosidic linkage in 4-O-methylglucuronic acid (MG) residue at mainly 220–230 °C under 10 MPa. At subsequent stage of 230 °C/10 MPa, X _n Ac _m were predominantly recovered. As the treatment was prolonged at 230 °C, X _n Ac _m were reduced, but remained to some extent, indicating that the acetyl group which is hydrolyzed to be acetic acid is more resistant than MG residue. In such a stage of treatment, cellulose started to hydrolyze to cello-oligosaccharides. These lines of evidence can clearly indicate the hydrolysis pathway of native O-acetyl-4-O-methylglucuronoxylan as treated by hot-compressed water. Thus, xylo-oligosaccharides recovered in a very early stage of the semi-flow hot-compressed water treatment preserve native O-acetyl-4-O-methylglucuronoxylan.     

Changes in soil carbon during the establishment of a hardwood plantation in subtropical Australia

Soil carbon (C) pools are not only important to governing soil properties and nutrient cycling in forest ecosystems, but also play a critical role in global C cycling. Mulch and weed control treatments may alter soil C pools by changing organic matter inputs to the forest ecosystem. We studied the 12-month mulch and weed control responses on the chemical composition of soil organic C and the seasonal dynamics of water extractable organic C (WEOC), hot water extractable organic C (HWEOC), chloroform-released organic C (CHCl₃-released C), and acid hydrolysed organic C (acid hydrolysable C) in a hardwood plantation of subtropical Australia. The results showed that compared with the non-mulch treatment, the mulch treatment significantly increased soil WEOC, HWEOC, and CHCl₃-released C over the four sampling months. The weed control treatment significantly reduced the amount of HWEOC and CHCl₃-released C compared with the no weed control treatment. Neither the mulch nor weed control treatment significantly affected soil acid hydrolysed organic C. There were no significant seasonal variations in soil WEOC, HWEOC, CHCl₃-released C, and acid hydrolysed organic C in the hardwood plantation. Solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy was used to study the structural chemistry of soil C pools in hydrofluoric acid (HF) treated soils collected 12 months after the mulch and weed control treatments were applied. Overall, O-alkyl C was the dominant C fraction, accounting for 33–43% of the total NMR signal intensity. The mulch treatment led to higher signal intensity in the alkyl C spectral region and A/O-A ratio (the ratio of alkyl C region intensity to O-alkyl C region intensity), but lower signal intensity in the aryl C and aromaticity. Compared with the no weed control treatment, the weed control treatment reduced signal intensity in the aryl C and aromaticity. Together, shifts in the amount and nature of soil C following the mulch and weed control treatments may be due to the changes in organic matter input and soil physical environment.     

Photosynthesis,water and nitrogen use efficiencies of four paper birch (Betula papyrifera) populations grown under different soil moisture and nutrient regimes

A greenhouse experiment was conducted to determine how four populations of paper birch (Betula papyrifera Marsh.), adapted to particular temperature, water and photoperiod regimes responded physiologically to different soil water and nutrient regimes. Seedlings of each of the four populations (Eaglet, LeeCreek, Porcupine and Skeena) from British Columbia were planted in pots and subjected to high and low water and nitrogen regimes for 4 months. Net photosynthesis (A), stomatal conductance (g_s), water use efficiency (WUE) and nitrogen use efficiency (NUE) were measured and compared among treatments. Trade-offs between WUE and NUE were examined. Soil moisture was the major factor affecting A for all the populations. All populations showed relatively high A in the high-water and high-nitrogen (HWHN) treatment, ranging from 8.5 to 9.9 μmol CO₂ m⁻² s⁻¹. Photosynthesis of trees in the low-water and high-nitrogen (LWHN) treatment was about 45% of that in the HWHN treatment. There was a linear increase in A as g_s increased in all populations. A decreased with increasing vapor pressure deficit (VPD). The populations demonstrated significantly different relationships between A and g_s, and VPD, with the LeeCreek population being the most conservative. This may provide a physiological basis for provenance selection and seed transfer. Eaglet and LeeCreek populations had lower WUE at the same level of NUE compared with Porcupine and Skeena populations. Porcupine and Skeena populations may be more suitable for moist sites due to their greater capacity to sequester water quickly, while the LeeCreek and Eaglet populations may be more suitable for drier interior sites where long drought periods can occur.     

Effect of seed treatment for laboratory germination of Albizia chinensis

Seeds of Albizia chinensis(Osb.) Merr. in addition to water were also treated with different treatments by incubating in ethyl alcohol, acetone, and petroleum ether at room temperature for different du...     

Investigation of changes in compressed moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>) after hot-press molding

In this study, molding moso bamboo strips to a curved shape using hot-press molding operation was explored. Bamboo strips with different thickness and moisture content (MC) were subjected to press molding under 120–210 °C for different time. Changes in the chemical components of bamboo were analyzed by Fourier-transform infrared spectroscopy (FTIR). Effect of MC on thermal mechanical behavior of bamboo was investigated using dynamic mechanical analysis (DMA). Results showed that the influencing degree of four variables on compression and recovery ratios decreased as: temperature?>?time?>?thickness?>?MC. Compression ratio increased and recovery ratio decreased dramatically when pressing temperature exceeded 180 °C. FTIR analysis indicated that polysaccharide (especially hemicelluloses) underwent a progressive thermal degradation during compression at 180 and 210 °C for 40 min, whereas relative content of lignin increased. DMA results showed that bamboo samples with a higher MC had a lower storage modulus value, confirmed water had a plasticizing effect. The loss factor of bamboo with higher MC (12 and 16%) exhibited two major transitions centred around 100 °C (α₁) and 50 °C (α₂), respectively. The temperature of these α transitions kept almost unchanged as moisture level increased from 12 to 16%. These findings provide fundamental information for the future preparation of curved bamboo as profiled components in engineered products.     

Effect of nanofillers on flame retardancy, chemical resistance, antibacterial properties and biodegradation of wood/styrene acrylonitrile co-polymer composites

Wood polymer nanocomposites (WPNCs) based on simul wood (Bombex ceiba, L.) were prepared by impregnation of styrene acrylonitrile copolymer, γ-methacryloyloxy trimethyl silane-modified TiO₂, SiO₂ nanoparticles and nanoclay intercalating mixture through vacuum impregnation. The impact of nanofillers on the physical properties, flame retardancy, water resistance, anti-swelling efficiency and biodegradability of the resultant WPNCs was investigated. Remarkable enhancement in wood properties such as flame retardancy, water resistance and anti-swelling efficiency was achieved with the treatment. The results showed that all the properties were maximum for wood samples treated with SAN/TiO₂ (0.5 %)/SiO₂ (0.5 %)/nanoclay (0.5 %). The presence of TiO₂ nanoparticles in WPNC exhibited antibacterial activity. The resistance to biodegradation was observed by incorporation of nanofillers into wood.     

A comparative study of extraction methods reveals preferred solvents for cystine knot peptide isolation from Momordica cochinchinensis seeds

MCoTI-I and MCoTI-II (short for Momordica cochinchinensis Trypsin Inhibitor-I and -II, respectively) are attractive candidates for developing novel intracellular-targeting drugs because both are exceptionally stable and can internalize into cells. These seed-derived cystine knot peptides are examples of how natural product discovery efforts can lead to biomedical applications. However, discovery efforts are sometimes hampered by the limited availability of seed materials, highlighting the need for efficient extraction methods. In this study, we assessed five extraction methods using M. cochinchinensis seeds, a source of well-characterized cystine knot peptides. The most efficient extraction of nine known cystine knot peptides was achieved by a method based on acetonitrile/water/formic acid (25:24:1), followed by methods based on sodium acetate (20 mM, pH 5.0), ammonium bicarbonate (5 mM, pH 8.0), and boiling water. On average, the yields obtained by these four methods were more than 250-fold higher than that obtained using dichloromethane/methanol (1:1) extraction, a previously applied standard method. Extraction using acetonitrile/water/formic acid (25:24:1) yielded the highest number of reconstructed masses within the majority of plant-derived cystine knot peptide mass range but only accounted for around 50% of the total number of masses, indicating that any single method may result in under-sampling. Applying acetonitrile/water/formic acid (25:24:1), boiling water, and ammonium bicarbonate (5 mM, pH 8.0) extractions either successively or discretely significantly increased the sampling number. Overall, acetonitrile/water/formic acid (25:24:1) can facilitate efficient extraction of cystine-knot peptides from M. cochinchinensis seeds but for discovery purposes the use of a combination of extraction methods is recommended where practical.     

Pressurized hot water extraction of Norway spruce hemicelluloses using a flow-through system

Norway spruce saw meal was extracted with pressurized hot water at 120–240°C using a flow-through system. Only small amounts of hemicelluloses were extracted at 120–160°C, but dissolution was significantly enhanced when higher extraction temperatures were applied. All hemicelluloses but only 15% of lignin were removed from wood at 220°C, and even less lignin was extracted at lower temperatures. Partial degradation of cellulose seemed to take place only at 240°C. Of the total amount of extracted hemicelluloses, 4–22% was hydrolyzed to monosaccharides. Although the average molar masses of extracted hemicelluloses decreased with increasing extraction temperature, even at 240°C the extracted carbohydrates occurred, on average, as polysaccharides. Polysaccharides with an average molar mass of 31 kDa were obtained at 170°C. The molecular-mass characteristics and yield of carbohydrates depend on the extraction temperature, which should be chosen based on the end use of the isolated hemicelluloses.     

Chemical characterization of wood and extractives of fast-growing Schizolobium parahyba and Pinus taeda

This study aims to evaluate the chemical composition of wood and extractives of Pinus taeda and Schizolobium parahyba (guapuruvu) as potential feedstock for new applications in the biorefinery industry. For this purpose, their content of α-cellulose, hemicellulose, insoluble lignin, hot water solubility, NaOH_1% solubility, inorganic materials (ash), and monomeric sugars by high-performance liquid chromatography was quantified. Attenuated total reflectance infrared spectroscopy and thermogravimetric analysis were also used to complete the physicochemical characterization of the studied woods. The extractives were obtained by soxhlet extraction with ethanol:toluene and dichloromethane and identified with pyrolysis-gas chromatography/mass spectroscopy technique. The results showed that guapuruvu wood has the higher amount of hemicellulose (16%) when compared to pine wood (10%), which resulted in higher solubility in alkali solution. Furthermore, in relation to other biomasses, the two woods presented more percentage of lignin and minor content of hemicelluloses. The P. taeda wood presented the highest percentage of extractives mainly composed of fatty acids and aromatic hydrocarbons, while guapuruvu wood had a higher percentage of phenolic compounds and also fatty acids. Both the materials have low content of extractives with dichloromethane and were mainly composed of lipophilic compounds.     

Influence of surface charge on viscosity behavior of cellulose microcrystal suspension

Microcrystalline cellulose with minimal surface charge was prepared from softwood kraft pulp via hydrolysis by 4N hydrochloric acid instead of sulfuric acid. To this material, sulfate ester groups as surface charge were introduced by treating with 55% (w/w) sulfuric acid. A treatment at 60°C for 2h gave nearly the same level of surface charge as that of the H₂SO₄ -hydrolyzed microcrystal. The number of sulfate groups were controlled by changing the H₂SO₄ treatment conditions. Although the microscopic size and shape of the microcrystalline particles were the same irrespective of the preparation method, the introduction of surface charge drastically reduced the viscosity and removed its time dependence. These changes in viscosity behavior are considered to result from charge-induced dispersion of loose aggregates existing in the initial charge-free microcrystals prepared by HCl hydrolysis.Part of this report was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

Effects of stem girdling on cone yield and endogenous phytohormones and metabolites in developing long shoots of Douglas-fir (Pseudotsuga menziesii)

Stem-girdling treatments were applied in early spring to stimulate cone formation in two genotypes of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco). After girdling treatments, male cone yield increased significantly in the next growing season. The increase was 14-fold in genotype 9137. In genotype 9550, more than 8,700 male cones were induced from each tree whereas no male cones were found in controls. Female cone yield was zero in controls and low for girdled trees in both genotypes. Multiple phytohormone-related compounds, including gibberellins (GAs), cytokinins, indole-3-acetic acid (IAA), abscisic acid (ABA) and their selected metabolites, were analyzed in developing long shoots after girdling treatments by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC?CESI?CMS/MS) in multiple reaction monitoring mode. Concentrations of GA₄ were slightly higher at week 2 following girdling treatment, whereas at week 8 lower GA₄ concentrations were found in girdled samples. Stem girdling did not affect concentrations of IAA and major cytokinins, such as zeatin riboside and isopentenyl adenosine. Concentrations of ABA differed two-fold between the genotypes. Although girdling treatment did not cause differences in ABA concentrations, it generally resulted in higher concentrations of ABA glucose ester. Concentration increase of 7??-hydroxy ABA by girdling was only found in genotype 9550 at week 8. Girdling caused little change in concentrations of phaseic acid in both genotypes.     

Effects of water stress on emission of volatile organic compounds by <Emphasis Type="Italic">Vicia faba</Emphasis>, and consequences for attraction of the egg parasitoid <Emphasis Type="Italic">Trissolcus basalis</Emphasis>

When plants are damaged by herbivorous insects, blends of volatile organic compounds (VOCs) are induced and released and can also be used by parasitoids to locate hosts. The aim was to determine whether VOCs induced by water stress affect the plant–herbivore–parasitoid system represented by broad bean (Vicia faba; Fabales: Fabaceae) stink bug (Nezara viridula; Heteroptera: Pentatomidae) egg parasitoid (Trissolcus basalis; Hymenoptera: Platygastridae). The effects of water stress (expressed as the percentage fraction of transpirable soil water [FTSW] supplied) alone and in combination with N. viridula damage (feeding plus oviposition) were determined according to: (1) the behavioural response of the egg parasitoid in a Y-tube olfactometer and (2) the plant VOCs collected and analysed by thermal desorption–gas chromatography–mass spectrometry. With pot water capacity as FTSW₁₀₀, water stress was applied as mild (FTSW₈₀), moderate (FTSW₅₀) and severe (FTSW₁₀). Bioassays with plants under abiotic stress alone showed that egg parasitoids are more attracted by FTSW₁₀ plants than by well-watered plants. When plants were under abiotic and biotic stress interactions, the egg parasitoids are more attracted by FTSW₁₀ and FTSW₅₀ plants than by well-watered plants infested with N. viridula. Considering VOCs emissions, projection to latent structures discriminant analysis (PLS-DA) separated treatments according to egg parasitoid responses. Water stress alone and in combination with biotic stress induced changes in VOC emissions of V. faba plants that attract egg parasitoids. These findings contribute to our understanding of how water stress affects the interactions between plants, insect pests and egg parasitoids.     

干旱胁迫下5种幼苗光合特性的研究

以该区年龄相同的5种主要植被恢复树种车桑子、滇柏、侧柏、花椒和香樟幼苗为研究对象,通过盆栽控水试验,测算其在不同水分梯度下的叶绿素相对含量、净光合速率、蒸腾速率、气孔导度、胞间CO₂浓度以及水分利用效率等生理生态指标,系统比较各参数的适应性变化及其差异性分析,结果表明：（1）随着干旱胁迫的加剧,5种幼苗叶片叶绿素相对含量呈现不同的变化趋势,车桑子逐渐降低,侧柏和滇柏先降后升,花椒和香樟先升后降;（2）各光合生理生态参数也呈现不同的变化规律：随干旱胁迫的加剧,净光合速率、蒸腾速率、气孔导度均逐渐降低,且在中度和重度干旱胁迫时极显著降低,其中在重度干旱胁迫时,侧柏的净光合速率最低比对照下降了100.5%,下降幅度最大;胞间CO₂浓度在轻度干旱胁迫时下降,中度和重度干旱胁迫时上升;水分利用效率在轻度和中度干旱胁迫时增加,重度干旱胁迫时下降,其中香樟的水分利用效率在重度干旱胁迫时仍是对照的1.05倍;（3）综合分析各项生理生态参数,5种幼苗均能耐受一定程度的干旱胁迫,但香樟的控水耐旱能力明显高于其它4种树种,更能适应石漠化地区的生态环境。     

Effects of Water and Nutrient Availability in Pinus pinaster Ait. Open Pollinated Families at an Early Age: Growth, Gas Exchange and Water Relations

Growth and physiological responses of Pinus pinaster Ait. to water and nutrient availability were compared in four open pollinated families of Arenas de San Pedro provenance (Central Iberian Peninsula), looking for more useful parameters and growing conditions to be included in early selection programmes of forest trees. Young seedlings were grown in a greenhouse, subjected to high and low water and nutrient regimes, during 14 weeks. Interfamily differences were significant with regard to growth, nutrient content and water-use efficiency (WUE): differences in growth were higher under more favourable growing conditions; gas exchange differences were higher in the short term (9 weeks), indicating a faster reaction to water stress of the better adapted families to these conditions; the highest growth rates were found in the families with the largest plasticity, highest WUE and highest nutrient content. Water regime and nutrients had significant effects on growth, δ¹³C, gas exchange and water relation parameters. For these parameters the ranking of the families was kept regardless the water × nutrient supply combination and there was not a significant family × treatment interaction. In the long term (14 weeks) higher water supply and nutrient content significantly increased instantaneous WUE. The positive relationships between growth, intrinsic WUE (A/g _wv) and δ¹³C demonstrate that it should be possible to use physiological parameters (e.g. g _wv, δ¹³C) as a surrogate for the efficiency in the use of water, at least if short periods of water stress (up to 2 months long) were frequent, as it occurs in the Mediterranean basin. There was also some indication that the decrease in nitrogen or potassium supply led to increasing stomatal conductance and hence lower WUE.