Maximum Water Loss Research Articles

Optimisation of osmotic dehydration of carrot cubes in sucrose-salt solutions using response surface methodology

Osmotic dehydration of carrot cubes in ternary solution of water, sucrose and sodium chloride at different solution concentrations, temperatures and process durations were analysed for water loss and solute gain during osmotic dehydration. The osmotically pre-treated carrot cubes were further dehydrated in a cabinet dryer at 65 °C and were then rehydrated in water at ambient temperature of water for 10–12 h and were analysed for rehydration ratio, shrinkage and overall acceptability after rehydration. The process was optimised for maximum water loss, rehydration ratio and overall acceptability of the rehydrated product, and for minimum solute gain and shrinkage of rehydrated product by response surface methodology. The optimum conditions of various process parameters are 50°B+10% w/v aqueous sodium chloride concentration, 46.5 °C solution temperature and 180 min process duration.

Optimization of osmotic dehydration of potato using response surface methodology

Response surface methodology was used to determine the optimum processing conditions that yield maximum water loss and weight reduction and minimum solid gain and water activity during osmotic dehydration of potatoes. Temperature (20–60 °C), processing time (0.5–8 h), sucrose (40–60% w/w) and salt (0–15% w/w) concentrations were the factors investigated with respect to water loss (WL), solid gain (SG), weight reduction (WR) and water activity ( a w). Experiments were designed according to Central Composite Rotatable Design with these four factors each at five different levels, including central and axial points. Experiments were conducted in a shaker (Thermoshake-Gerthardt) with constant agitation of 200 rpm and solution to sample ratio of 5/1 (w/w). With respect to water loss, solid gain, weight reduction and water activity, both linear and quadratic effects of four variables were found to be significant. For each response, second order polynomial models were developed using multiple linear regression analysis. Analysis of variance (ANOVA) was performed to check the adequacy and accuracy of the fitted models. The response surfaces and contour maps showing the interaction of process variables were constructed. Applying desirability function method, optimum operating conditions were found to be temperature of 22 °C, sucrose concentration of 54.5%, salt concentration of 14% and treatment time of 329 min. At this optimum point, water loss, solid gain, weight reduction and water activity were found to be 59.1 (g/100 g initial sample), 6.0 (g/100 g initial sample), 52.9 (g/100 g initial sample) and 0.785, respectively.

Critical thermal maximum and body water loss in first instar larvae of three Cetoniidae species (Coleoptera)

Critical thermal maximum (CT max) and body water losses were measured in first instar larvae of Gnorimus nobilis, Osmoderma eremita (Trichiinae) and Cetonischema aeruginosa (Cetoniinae) when air temperature was increased gradually (0.5 °C/min) from 20 °C to the critical thermal maximum (CT max), in dry air (near 0% R.H.). The CT max was significantly lower in O. eremita (45.6±0.7 °C) than in G. nobilis (48.5±0.6) and C. aeruginosa (51.4±0.9 °C). An increase of 10 °C (30–40 °C) induced a 2-fold increase of the water loss in C. aeruginosa and O. eremita ( Q 10=2.10±0.12 and 2.13±0.20, respectively). In the range from 40 to 45 °C to CT max a strong increase of the water loss was observed in O. eremita and C. aeruginosa, respectively. Body water losses were significantly lower in C. aeruginosa than in O. eremita and G. nobilis over the range 20 °C—CT max; no significant difference occurred between G. nobilis and O. eremita.

The effect of vapor pressure deficit on leaf area and water transport in flower stems of soil-less culture rose

The effect of indoor air relative humidity on leaf area and water transport of flower stems in a greenhouse rose crop (Rosa X hybrida cv Mercedes) grown on a soil-less substrate was studied on 2-year-old plants, in a freely draining irrigated system ensuring a high leaching fraction. In one compartment of the greenhouse, the roof opened when the air temperature reached 28 °C. In the other, an evaporative wet pad and fans were operated at 28 °C. The wet pad treatment decreased vapor pressure deficit (VPD). A maximum VPD difference of 1.45 kPa between the two compartments occurred during the noon-hours on a warm day with high atmospheric evaporative demand. On days with moderate evaporative demand, the wet pad was either not operated or when operated, produced VPD differences smaller than 1.45 kPa. Wet pad treatment decreased the transpiration rate per unit leaf area of the flower stem. On a typical summer day, with high evaporative demand, mean maximum water loss per unit leaf area was 2.63 ± 0.13 and 1.79 ± 0.09 kg m −2 day −1 for the high and low VPD compartments, respectively. However, low VPD decreased only slightly mean daily water flow per stem: 104.3 ± 6.9 g at low VPD versus 112.4 ± 8.7 g at high VPD (not significant at p > 0.05), despite the significant differences ( p > 0.05) in VPD between the greenhouse compartments. The wet pad treatment mitigated leaf water potential drop at noon-time. The results suggest that rose flower stems adapt to high VPD by decreasing leaf area for maintaining high sap flow rate per unit area.

Estimating Percolation and Lateral Water Flow on Sloping Land in Rainfed Lowland Rice Ecosystem

Quantifying water losses in paddy fields assists estimation of water availability in rainfed lowland rice ecosystem. Little information is available on water balance in different toposequence positions of sloped rainfed lowland. Therefore, the aim of this work was to quantify percolation and the lateral water flow with special reference to the toposequential variation. Data used for the analysis was collected in Laos and northeast Thailand. Percolation and water tables were measured on a daily basis using a steel cylindrical tube with a lid and perforated PVC tubes, respectively. Percolation rate was determined using linear regression analysis of cumulative percolation. Assuming that the total amount of evaporation and transpiration was equivalent to potential evapotranspiration, the lateral water flow was estimated using the water balance equation. Separate perched water and groundwater tables were observed in paddy fields on coarse-textured soils. The percolation rate varied between 0 and 3 mm/day across locations, and the maximum water loss by lateral movement was more than 20 mm/day. Our results are in agreement with the previously reported findings, and the methodology of estimating water balance components appears reasonably acceptable. With regard to the toposequential variation, the higher the position in the topoesquence, the greater potential for water loss because of higher percolation and lateral flow rates.

New approaches to the visualization, quantification and explanation of acid-induced water loss from Ca-alginate hydrogel beads

The water loss of Ca-alginate hydrogels at pHs below 4.0 was visualized with 1HNMR-imaging by covering a single alginate bead with cyclohexane-d12 in a specially equipped NMR-tube and adding propionic acid at defined concentrations. The exact amount of water expelled from the beads was calculated from their weight loss and correlated with the acid concentrations and pHs within the hydrogel matrix. The maximum water loss of 52% (w/w) occurred at pH 1.0, while only 5% (w/w) of the initial water content were lost at pH 3.6. The analysis of the water collected from several alginate beads for Ca2+-ions and free polysaccharides led to the assumption that, due to the acid-induced protonation of the carboxyl functions, the ionotropic network is gradually converted to an alginic acid gel structured by H-bonds. This contradicts existing theories explaining the pH-induced water loss by a lower solubility of the alginate chains and decreased repulsion between protonated carboxyl functions, but explains previously reported pH-dependent alterations of mass transport and drug retention of Ca-alginate gels. Thus, the presented experiments enable a more precise and complete view of the acid-induced process within Ca-alginate hydrogels. The transfer to the characterization of other hydrogels is possible and should be advantageous, especially if a calibration of the NMR-measurement could be achieved.

Properties of Plastic, Peat, and Processed Poultry Feather Fiber Growing Containers

When the substrate surface and drainage holes of feather fiber, peat, and plastic containers were sealed with wax, hyperbolic growth curves were good fits to cumulative water loss on a per container and per cm2 basis, with R2 values ranging from 0.88 to 0.96. The effect of container type was significant as the differences in asymptotic maximum water loss (max) values for all container pairs were significant at P < 0.05 for both water loss per container and water loss per cm2. The predicted total water loss for peat containers was ≈2.5 times greater than feather containers, and the predicted water loss per cm2 for the peat container was ≈3 times greater than feather containers. Vinca [Catharanthus roseus (L.) G. Don.] `Cooler Blush' and impatiens (Impatiens walleriana Hook f.) `Dazzler Rose Star' plants grown in feather and peat containers required more water and more frequent irrigations than those grown in plastic containers. However, plants grown in feather containers required less water and fewer irrigations than plants grown in peat containers. The surface area of containers covered by algal or fungal growth was significantly higher on peat containers than on feather containers. No fungal or algal growth was observed on plastic containers. Additionally, primarily algae were observed on peat containers whereas most discoloration observed on feather containers was due to fungal growth. Dry feather containers had a higher longitudinal strength than dry plastic containers but a lower longitudinal strength than dry peat containers. Wet feather containers had higher longitudinal strength than wet peat containers but a similar longitudinal strength as wet plastic containers. Dry feather and plastic containers had similar lateral strengths and both had significantly higher lateral strength than dry peat containers. Wet feather containers had significantly lower lateral strength than wet plastic containers but had higher lateral strength than wet peat containers. Dry and wet plastic containers had higher punch strength than wet or dry peat and feather containers. Dry peat containers had significantly higher punch strength than dry feather containers. However, wet feather containers had significantly higher punch strength than wet peat containers. Decomposition of peat and feather containers was significantly affected by container type and the species grown in the container. When planted with tomato (Lycopersicum esculentum L.) `Better Boy', decomposition was not significantly different between the peat and feather containers. However, when vinca and marigold (Tagetes patula L.) `Janie Bright Yellow' were grown in the containers, decomposition was significantly higher for feather containers than for peat containers. Therefore, containers made from processed feather fiber provided a new type of biodegradable container with significantly improved characteristics as compared to peat containers.

Modelling for moisture variation during osmo-concentration in apple and pineapple

A mathematical model for prediction of moisture content in apple and pineapple during osmo-concentration was developed using both water loss and sugar gain as input variables. The model predicts theoretical maximum water loss from osmotic pressure equilibrium considerations. Using water diffusivity and `sugar–water diffusion quotient' as the primary variables, sugar diffusivity, sugar gain, water loss and moisture contents could be predicted at different temperatures (30, 40 and 50 °C) and concentrations (50, 60 and 70°Bx) of sucrose solution. Theoretical maximum water loss was found to vary between 0.69–0.81 kg water kg slice −1 for apple and 0.64–0.77 kg water kg slice −1 for pineapple. Predicted values of water diffusivity varied between 0.78–3.46 × 10 −10 m 2 s −1 for apple and 1.90–4.35 × 10 −10 m 2 s −1 for pineapple. The average value of `sugar–water diffusion quotient' was found to be 3.53 ± 0.652 and 4.07 ± 0.776 for apple and pineapple, respectively. The actual and predicted values of moisture contents in the two fruits were found to have good agreement with a relative deviation percent below 10%.

Modelling for moisture variation during osmo-concentration in apple and pineapple

A mathematical model for prediction of moisture content in apple and pineapple during osmo-concentration was developed using both water loss and sugar gain as input variables. The model predicts theoretical maximum water loss from osmotic pressure equilibrium considerations. Using water diffusivity and `sugar–water diffusion quotient' as the primary variables, sugar diffusivity, sugar gain, water loss and moisture contents could be predicted at different temperatures (30, 40 and 50 °C) and concentrations (50, 60 and 70°Bx) of sucrose solution. Theoretical maximum water loss was found to vary between 0.69–0.81 kg water kg slice−1 for apple and 0.64–0.77 kg water kg slice−1 for pineapple. Predicted values of water diffusivity varied between 0.78–3.46 × 10−10 m2 s−1 for apple and 1.90–4.35 × 10−10 m2 s−1 for pineapple. The average value of `sugar–water diffusion quotient' was found to be 3.53 ± 0.652 and 4.07 ± 0.776 for apple and pineapple, respectively. The actual and predicted values of moisture contents in the two fruits were found to have good agreement with a relative deviation percent below 10%.

Optimisation of Osmotic Dehydration of Cashew Apple (Anacardium Occidentale L.) in Sugar Solutions

Osmotic dehydration of cashew apple in sucrose and corn syrup solids solutions as influenced by temperature (30-50 C), sugar syrup concentration (40-60% w/w) and immersion time (90-240 min) was studied through response surface methodology. Responses of water loss (%) and solid gain (%) were fitted to polynomials, with multiple correlation coefficients ranging from 0.92 to 0.99. The fitted functions were optimised for maximum water loss and minimised incorporation of solids in order to obtain a product resembling non-processed fruit. Three optimum sets were selected for each solute and the ascorbic acid content was determined. The ascorbic acid losses were similar to those reported for osmotic dehydration processes.

Validation of the doubly labeled water method under low and high humidity to estimate metabolic rate and water flux in a tropical snake (Boiga irregularis).

This study uses indirect calorimetry to assess the effects of humidity on the accuracy of the doubly labeled water (DLW) technique to predict metabolic rate and water flux in brown treesnakes (Boiga irregularis). The DLW technique accurately predicted total water efflux in brown treesnakes under low-humidity conditions and found that the total number of water molecules exchanged with the environment under humid conditions was not significantly different than maximum net total evaporative water loss under low humidity conditions plus fecal water loss. Because of changes of total body water of >12%, the DLW technique overestimated metabolic rate by a factor of 2.2 under low-humidity conditions. Under high-humidity conditions, the DLW technique overestimated metabolic rate in brown treesnakes by a factor of 4.6. Researchers using the DLW technique in humid or moist environments should be cautious because this study indicates that DLW estimates of metabolic rate may be inflated when large amounts of water vapor are exchanged through the skin or respiratory passages.

Thermoregulatory physiology of the Crested Pigeon Ocyphaps lophotes and the Brush Bronzewing Phaps elegans.

The metabolic physiology of the Crested Pigeon (Ocyphaps lophotes) and the Brush Bronzewing (Phaps elegans) is generally similar to that expected for birds of their size, but the Crested Pigeon has a number of characteristics which would aid survival in hot and dry regions. Body temperature increased similarly for the Crested Pigeon (from 38.8 degrees C to 41.5 degrees C) and the Brush Bronzewing (39.3 degrees C to 41.4 degrees C) over ambient temperatures (T(a)s) from 10 degrees C to 35 degrees C. Both species became hyperthermic (body temperature, T(b)>42 degrees C) at T(a)=45 degrees C. Basal metabolic rate of the Crested Pigeon (0.65 ml O(2) g(-1) h(-1) at 40 degrees C) was approximately 71% of that predicted for a columbid bird, while BMR of the Brush Bronzewing (0.87 ml O(2) g(-1) h(-1) at 20 degrees C to 40 degrees C) was approximately 102% of predicted. Total evaporative water loss increased exponentially with T(a) for both species, from <1 mg H(2)O g(-1) h(-1) at 10 degrees C to >12 mg H(2)O g(-1) h(-1) at 45 degrees C. It was similar and low for both species at T(a)<30 degrees C, but was higher for the Brush Bronzewing than the Crested Pigeon at T(a)>30 degrees C. Ventilatory minute volume matched oxygen consumption, such that oxygen extraction efficiency did not change with T(a) and was similar for both species (approximately 20%). Expired air temperature was considerably lower than T(b) for both species at T(a)<35 degrees C, potentially reducing respiratory water loss by approximately 65% at T(a)=10 degrees C to approximately 30% at T(a)=35 degrees C. Cutaneous evaporative cooling was significant for both species, with skin resistance decreasing as T(a) increased. The Crested Pigeon had a lower skin resistance than the Brush Bronzewing at T(a)=45 degrees C. The Brush Bronzewing had apparently reached its maximum cutaneous water loss at 30 degrees C and relied on panting to cool at higher T(a).

Altered Water Barrier Function in Epidermal-Type Fatty Acid Binding Protein-Deficient Mice

We have generated mutant mice for epidermal-type fatty acid binding protein by the gene targeting technique and examined the phenotype in detail. Despite a lack in the expression of epidermal-type fatty acid binding protein mRNA and its protein in the skin and other tissues of the mutant mice, the animals appeared normal in gross and histologic examination. Northern blot analysis of other fatty acid binding proteins revealed a distinct elevated gene expression of heart-type fatty acid binding protein in the skin of the homozygous mice. In analyses of the skin, no differences were observed in contents of major fatty acids, electron microscopic appearance as well as inflammatory responses in ear skin between the mutant and wild-type mice. Basal transepidermal water loss of homozygous mice was lower than that of the wild mice. When acetone was applied to the skin for disruption of the water permeability barrier, recovery in transepidermal water loss was delayed, although maximum transepidermal water loss upon acetone treatment was similar between homozygous and wild-type mice in terms of size and time course. The molecular mechanism by which epidermal-type fatty acid binding protein contributes to the water barrier function of the skin remains to be elucidated.

Changes in desiccation resistance during development in the millipedePolydesmus angustus

SummaryWater loss at increasing temperature in dry air (&lt; 5% r.h.) was measured for the eight stadia ofPolydesmus angustusLatzel (Diplopoda, Polydesmida: Polydesmidae). Instantaneous rates of water loss, expressed as percentages of original body water, were calculated at 20, 25 and 30°C. At each temperature, the rate of water loss varied greatly among stadia, decreasing between 15‐ and 18‐fold from stadium I to stadium VII, and then significantly increasing from stadium VII to stadium VIII (adult). In all stadia, the rate of water loss increased with rising temperature, but the temperature effect was much more pronounced in juveniles than in larger stadia. The threshold temperature of heat stupor, which was measured from stadium IV onwards, increased significantly during development, from 35.6°C in stadium IV to 39.5°C in adults. Survival at 20°C and 76% r.h. varied as could be expected from the water loss rates in dry air, survival time increasing from stadium I to stadium VII and then decreasing from stadium VII to the adult stage. The maximum tolerable water loss, estimated for stadia V, VII and adults, did not change significantly among stadia (mean: 47% of the original water content), suggesting that survival times under desiccating conditions depended primarily on the rates of water loss. The relevance of the results in terms of summer survival under natural conditions is discussed, and it is concluded that juvenile mortality could be substantial in the field. This is important for understanding the adaptive value of cohort‐splitting inP. angustus.

Shelf life of beef from local Spanish cattle breeds stored under modified atmosphere

Beef steaks from six Spanish cattle breeds (Asturiana de los Valles, Morucha, Parda Alpina, Pirenaica, Rubia Gallega and Retinta) were packaged under modified atmosphere (60% O 2, 30% CO 2 and 10% N 2). Water loss, pH, thiobarbituric acid values (TBA), aerobic plate counts, lactic acid bacteria and Enterobacteriaceae counts, CIE L* a* b* colour values and the sensory properties of odour and colour were recorded before packaging (day 0) and after 5, 10 and 15 days of storage. A significant interaction ( P<0.05) between breed and storage time was found for all variables, except water loss. Values of pH were between 5.3 and 5.6; maximum water loss (2.64%) was reached after 10 days of storage; aerobic plate counts, lactic acid bacteria and Enterobacteriacea counts were lower than 10 7 CFU/g, and L* increased with storage time while a* decreased ( P<0.05). The maximum shelf life of beef assessed by sensory evaluation (regarding colour and odour degradation) was between days 5 and 10 in meat from Retinta breed and between days 10 and 15 in meat from the other breeds, shelf life was probably limited by lipid oxidation.

Criteria for estimating acceptable exposure times in hot working environments: a review.

To revise the criteria used in the present "Required Sweat Rate" standard ISO 7933 (1989) for the prediction of the maximum duration of work in hot environments. Review of the literature and in particular, of the bases for the present criteria. A new method is proposed, to take into account the increase in core temperature associated with activity in neutral environments. The prediction of maximum wetness and maximum sweat rates are revised, as well as the limits for maximum water loss and core temperature. An improved set of maximum values and limits is described, to be used in the revised version of the ISO 7933 standard. Due to the major modifications to the "Required Sweat Rate" index and in order to avoid any confusion, it is suggested that the revised model be renamed the "Predicted Heat Strain" (PHS) model.

Optimisation of osmotic preconcentration and fluidised bed drying to produce dehydrated quick-cooking potato cubes

Osmotic preconcentration followed by fluidised bed drying of potato pieces to produce dehydrated quick-cooking potato was studied. Process parameters of both operations were optimised using response surface methodology. Since solid gain affects taste of the product, the process was optimised for maximum water loss and minimum solid gain. A solution of 50% sugar and 10% salt at 47°C for 4 h was found to be optimum for osmotic preconcentration of potato cubes. Moisture content was reduced from 84% to 60% moisture content (w.b.). Minimisation of final moisture content and bulk density with acceptable colour was the basis for optimising the fluidised bed drying conditions. Drying at 140°C for 10 min at 5.3 m/s followed by thin layer air drying at 50–60°C and 0.75 m/s for about 7 h was found to be optimal. Time to rehydrate/cook the processed-potato was only half that for fresh-potato. Organoleptic overall acceptability of the cooked processed-potato was almost same as that of cooked fresh-potato.

Partitioning variance in a physiological trait: desiccation resistance in keratin beetles (Coleoptera, Trogidae)

1. Although variation in physiological traits forms the substance of evolutionary physiology, the way that this variation is partitioned among different hierarchical levels (e.g. population, species, genus) is not well known. 2. In this study variance partitioning is examined in body size, water content, lipid content, rate of water loss, maximum tolerable water loss and survival time at four levels (individual, population, species, genus) in southern African keratin beetles. 3. It is found that most variance in body size, and the physiological traits that are strongly influenced by body size (water and lipid content, maximum tolerable water loss, rate of water loss), is partitioned at the generic level (50–70%), then at the species level (20–50%) and finally at the population (1–9%) and individual (2–18%) levels. 4. On the other hand, variance in survival time, and variance in rate of maximum water loss once the effects of body size have been taken into account, are partitioned mostly at the species level (40–70%), whereas maximum tolerable water loss and lipid and water content show greatest variance at the individual level (63–75%). This is largely a consequence of differences in the extent of scaling of these traits. 5. The results suggest that where possible the effects of phylogeny should be controlled for when examining desiccation resistance in insects using comparative methods, but that confidence in conclusions from previous studies, which have used mass‐specific data, is not unwarranted.

Optimal irrigation efficiency for maximum plant productivity and minimum water loss

Castilla-La Mancha in Central Spain is a semi-arid area of extremely high interannual and seasonal rainfall variability. Average annual rainfall for the catchment of the Upper Guadiana using data from 60 rain gauges for October 1956–September 1991 varied from a minimum of 326 mm in October 1982–October 1983 to a maximum of 642 mm in October 1968–September 1969. The mean annual rainfall for the period was 495 mm with a coefficient of variation for annual rainfall of 26.4%. In addition to this the spatial variability of rainfall is particularly high. For example total annual rainfall varied from 200 to 1200 mm for the hydrological year October 1968–September 1969 over a distance of only 50 km. The mean annual rainfall for all 60 stations for the period 1956–1991 was 460 mm with a coefficient for spatial variation of 15%. Dryland farming which relies on these uncertain precipitation inputs is a high risk activity [Tarjuelo, J.M., de Juan, J.A., Valiente, M., Garcia, P., 1996. Agric. Water Manage. 31, 145–163] and over recent decades intensive irrigation has increased dramatically in order that precipitation inputs can be supplemented as required thereby allowing more stable agricultural productivity. The paper uses a coupled hydrology and vegetation growth model – PATTERN [Mulligan, M., 1996. Modelling hydrology and vegetation change in a degraded semi-arid environment. PhD. Thesis, University of London] to explore the relationship between irrigation and productivity for different soils typical of the Upper Guadiana catchment. Analysis of the model results shows that irrigation efficiency is highly sensitive to both soil texture and irrigation volume. Optimally efficient irrigation in terms of water losses occurs at the lowest volumes of applications. Fine grained soils are better suited to irrigation than coarse grained soils as losses to recharge are minimised. Coarse grained soils have large recharge losses and irrigation is also more sensitive to small changes in texture for coarser soils. Irrigation losses through recharge are also very sensitive to the interannual and spatial variability of rainfall.

Structural studies of tabasheer, an opal of plant origin

Abstract Two samples of hydrated silica from the bamboo plant (‘tabasheer’ and ‘bambusa’) were examined by X-ray fluorescence and 1H, 27Al and 29Si solidstate NMR, X-ray diffraction and thermogravimetric analysis. Silicon is the major elemental component of both samples, with much smaller amounts of aluminium (about 1·2 wt%), iron (0·3—0·4 wt%), calcium and magnesium, and traces of phosphorus. The maximum theoretical water loss calculated from the OH/Si ratio derived from the 29Si NMR spectra (4·92 and 3·82 wt% for the two samples) agrees with the weight loss measured by thermogravimetric analysis. Adsorbed water is evolved at temperatures below about 250°C, which is followed by gradual dehydroxylation. The water content of tabasheer is greater than that of bambusa, so that the initial rate of weight loss in both in tabasheer is higher. However, above about 250°C the rate of weight loss in both samples is very similar and the thermogravimetric curves are virtually parallel. The weight loss on dehydroxylation agrees with that calcualted from the OH content obtained by 29Si magic-angle spinning NMR. The presence of exclusively 4-coordinate (tetrahedral) aluminium in tabasheer shows that Al is part of the silicate network. Combined with the almost complete absence of aluminium from intracellular silica, this leads us to suggest that the role of extracellular silicon in bamboo is to exclude aluminium from the plant cells. 1H NMR spectra allow us to identify two kinds of hydroxyl group and to estimate the change of the proton—proton distance during dehydroxylation as a function of temperature for each kind of hydroxyl.