Dehydration Duration Research Articles

Mass transfer analysis and kinetic modeling of ultrasound-assisted osmotic dehydration of kiwifruit slices

Ultrasound treatments (sonication) in combination with osmotic dehydration process accelerate the rate of moisture removal from the fruits or vegetables pieces and decrease the dehydration duration. The purpose of this study was to examine the influence of ultrasound-assisted osmotic dehydration (UAOD) on mass transfer kinetic (soluble solids gain and moisture loss) of kiwifruit slices. The UAOD process was performed using 20, 30, and 40% sucrose solutions in ultrasonic bath (40 kHz, 75 and 150 W) for 10, 20, 30, 40, 50, 60, 70, and 80 min. After treatments, processed kiwifruit slices were dried at 70 °C using hot air oven. UAOD process reveals that mass reduction, soluble solid gain, moisture loss and rehydration capacity affected by treatments time, sucrose solution concentration and sonication power. The results showed that the UAOD treatment increased moisture loss and soluble solids gain. Furthermore, kiwifruit slices treated with higher ultrasound intensity (150 W) showed reduced dehydration duration (higher water loss), improved dehydration rate, and increased effective moisture diffusivity (Deff). The Deff determined by Fick's second law was varied from 9.05 × 10–11 to 29.28 × 10–11 m2s-1. The experimental data of dehydration curve of kiwifruit slices were fitted to different thin-layer equations and the Page equation with empirical constants was the best describing the of kiwifruit slices dehydration.

Development of efficient and sustainable droplet-vitrification cryoconservation protocol for shoot tips for long-term conservation of Dahlia germplasm

Dahlias are the one amongst the tuberous herbaceous plants, valued for their attractive colorful flowers with varied size cultivated due to its ornamental value as a potted plant or cut flower in many countries. Dahlia germplasm was being conserved in the in vitro Genebank of ICAR- NBPGR, New Delhi since 2005–06 under normal growth and slow growth with a regular subculturing in every 6 months and 1 year respectively, which is laborious and time-consuming. Hence, in the current study we attempted to develop an efficient droplet-vitrification cryopreservation protocol for safe and long-term conservation of dahlia germplasm. Significant effect of type and position of explants, plant vitrification solution-2 (PVS2) dehydration duration, pregrowth period and loading solution treatment duration on post-thaw regrowth after cryoconservation was observed. Shoot tips, each being 1.0 mm in length and 0.5 mm in width positioned at the tip of in vitro shoots with a similar developmental stage (similar shoot length) were excised from in vitro cultures pregrown for 6 wks on B5 basal medium supplemented with 0.5 mg/l BAP, 30 mg/l silver nitrate and 3% sucrose. The excised shoot tips were precultured on MS + 0.3 M sucrose for overnight followed by loading solution (2.0 M glycerol and 0.4 M sucrose in liquid MS medium) treatment for 80 min, PVS2 dehydration for 30 min and then transferred onto PVS2 droplets on aluminum foil strips and cryostored in liquid nitrogen (LN). An average of 44.44% post-thaw regrowth was obtained in six accessions tested and no significant difference among the accessions was observed. There was no significant loss in regrowth of cryostored shoot tips after 1 year and 6 years of cryobanking. This justifies the genotype-wide and sustainability of the protocol for cryoconservation of Dahlia germplasm using droplet-vitrification cryopreservation procedure in the cryobanks. To the best of our knowledge, this is the first report on cryoconservation of Dahlia germplasm.

Survival and State of Garlic Explants of Two Lithuanian Cultivars after Cryopreservation

Cryopreservation features of Lithuanian garlic (Allium sativum L.) cultivars ‘Žiemiai’ and ‘Dangiai’ were investigated. The survival rate and state of explants, depending on the type of explant, and dehydration conditions were evaluated in the experiment. Explants isolated from cloves and bulbils were dehydrated with a plant vitrification solution 3 (PVS 3) containing 50% w/v glycerol and 50% w/v sucrose in liquid MS medium. Three different exposure durations of 1.5, 2, and 3 h in PVS3 solution were applied at 0 °C. Unloaded stem domes were planted in Petri dishes with MS medium supplemented with 1 mg L−1 naphthaleneacetic acid (NAA) and 6–dimethylallylamino purine (2-iP) on 0.8% plant agar. The obtained results showed that the cryopreservation in liquid nitrogen reduced the survival rate of explants by 20–40%. The average number of surviving explants after freezing reached 64.3% for both cultivars. Cultivar ‘Žiemiai’ showed a 24% higher capability for survival than ‘Dangiai’. The total number of surviving explants of ‘Žiemiai’ reached 76.1%. Explants from bulbils were 23% more effective for cryopreservation compared to cloves. Evaluation of the effect of dehydration duration showed that the survival rate of the explants from bulbils of both cultivars was highest after treatment with PVS3 for 3 h and reached 91%. Treatment in PVS3 solution for 2 h was sufficient for survival of explants from cloves. Obtained results confirm that the efficiency of garlic cryopreservation depends on complex factors.

Morphology and Anatomy of Leaf, Stem and Petiole of Luvunga crassifolia Tanaka (Rutaceae)

Luvunga crassifolia is an underutilized plant in the Citrus family. Other than brief morphological descriptions, there are no published reports on other identification features of this plant. Thus, the current study was aimed to investigate macroscopic and microscopic diagnostic features of L. crassifolia leaves, stems, and petioles. Macroscopic characterization, optimization of histological procedure, and histochemical analyses of differential stains were carried out on the leaves, stems, and petioles of L. crassifolia. The histological method was optimized by modifying the following parameters: number of fixation days, dehydration duration with degraded series of ethanol or butanol, clearing duration, and infiltration duration. After infiltration, embedding and sectioning of the tissues were performed. Histochemical analyses were carried out using differential stains to identify the cellular components in leaf, stem and, petiole tissue sections. This study showed that L. crassifolia leaves are amphistomatic. Pellucid dots were observed on both adaxial and abaxial leaf surfaces. Secretory cavities, xylem, phloem, and pericyclic fibers were found in the cross-sections of leaf, stem, and petiole. Calcium oxalates were present in the leaf and stem sections, while trichomes were detected in stem and petiole sections. The information obtained from this study will be helpful for the identification and future taxonomic-related studies of this plant species.

A reasonable strategy for Caulerpa lentillifera J. Agardh (Bryopsidales, Chlorophyta) transportation based on the biochemical and photophysiological responses to dehydration stress

Caulerpa lentillifera is an economically important macroalgae. Many parental algae are needed in the commercial cultivation of C. lentillifera, and these algae are normally transported under dehydration. This study aimed to clarify the biochemical and photophysiological responses to dehydration stress to provide a theoretical basis for C. lentillifera transportation. The various biochemical and photophysiological changes to C. lentillifera were characterized during various lengths of dehydration stress. The relative water loss varied between 1.4% and 4.9% during dehydration periods of 2–120 h. Compared to the control, the contents of malondialdehyde, superoxide anion, and hydrogen peroxide during dehydration for 6–120 h increased significantly. Moreover, the chlorophyll fluorescence parameters (maximal photochemical efficiency of photosystem II, saturated photosynthetically active radiation, relative electron transport rate, and initial slope of rapid light curve) and the contents of chlorophyll a and soluble protein all decreased with increasing dehydration duration. These results suggest that dehydration could lead to oxidative stress in C. lentillifera. Compared to the control, the content of soluble polysaccharide and the activities of antioxidant enzymes (peroxidase, superoxide dismutase, and catalase) were both substantially enhanced at a certain stage of dehydration, and the proline content was relatively higher during all dehydration periods, indicating that these compounds probably play a crucial role in defensive reactions against dehydration-induced oxidative stress in C. lentillifera. After recovery for 72 h, the vegetative reproductive capability of C. lentillifera with a dehydration duration of 2–24 h was not significantly different from that of the control. Based on the above results, a reasonable strategy of maintaining dehydration within 24 h was proposed for C. lentillifera transportation. Moreover, photoinhibition easily occurs in C. lentillifera following rehydration after prolonged transportation, indicating that strong light stimulation should be avoided during the early recovery stage.

Anatomical changes and cytogenetic stability in bird of paradise plants after zygotic embryo cryopreservation by desiccation method

Bird of paradise (Strelitzia reginae Aiton.) is an ornamental plant of great economic value; however, the floricultural market is shaped by trends that vary throughout seasons and years. Thus, conservation techniques, such as cryopreservation, may be used for species and cultivar maintenance. It is important to understand the effect of low temperature used for cooling on the genetic stability and anatomical aspects of conserved species. The objective of this study was to evaluate the occurrence of anatomical changes and the maintenance of the cytogenetic stability of plants recovered from cryopreserved bird of paradise zygotic embryos. Zygotic embryos were cryopreserved in liquid nitrogen (+LN) after being dehydrated for 0, 30, and 60 min using silica gel (moisture content 16.79, 11.38, and 11.49%, respectively). Considering the dehydration duration, seedling development was higher (66.13%) in embryos that were cryopreserved after 30-min dehydration period, with no differences in the survival percentage during acclimatization, no anatomical changes in photosynthetic tissues, and no changes in the cytogenetic stability of the plants verified by flow cytometry. Thus, it is concluded that it is possible to cryopreserve bird of paradise zygotic embryos without changing the anatomy or genetic stability of the plants.

Comparison of Three Cryotechniques for Conservation of Banana (Musa AAA, Cavendish Subgroup) Genotypes

The aim of this study was to compare three cryotechniques, namely, droplet vitrification (DV), vitrification-cryo-plate (VCP) and dehydration-cryo-plate (DCP) on proliferating meristems of two Musa (AAA, Cavendish Subgroup) genotypes. The experiment was set up as factorial completely randomized design for the two Musa accessions (IC 250462 cv ‘Borjahaji’ and EC 493718 cv ‘Williams’) in five different dehydration duration (30 -150 min). Regrowth after cryopreservation in all treatments was predominantly of two types - shoot regeneration and callusing. In both the cultivars, shoot regrowth of non-frozen and LN treated meristems were not impacted significantly by duration of dehydration exposure, however, callus growth was significantly different with increasing time of exposure. The mean shoot regrowth for all dehydration treatments in Borjahaji was not significantly different. However, the VCP method in Williams, with mean shoot regrowth of 75.5 ± 2.8% was found to be significantly (P<0.05) better than that obtained from DV (63.1 ± 2.5%) and DCP (64.8 ± 1.9%). Quantitatively, highest shoot regrowth was obtained after 120 min PVS2 exposure in both cultivars, but using VCP method in Williams (86.7 ± 7.7%) and DV method in Borjahaji (73.1 ± 2.7%). Taking into consideration practical aspects for each technique, any of the three cryopreservation approaches can be used for cryobanking of proliferation meristems of Musa, as DV offers cost-effectiveness, while VCP and DCP have ease of explant handling, and DCP avoids chemical toxicity of PVS2.

Effects of radiation temperature on dehydration and moisture migration in banana slices during far‐infrared radiation drying

The changes in the various water states of bananas dried at different far-infrared radiation (FIR) temperatures were investigated via low-field nuclear magnetic resonance (LF-NMR). Results revealed that increasing FIR temperatures could significantly enhance drying rates. Scanning electron microscopy results demonstrated that FIR heating could produce additional porous structures in dried bananas and that porosity increased with the elevation of FIR temperatures. LF-NMR results revealed that high FIR temperatures were associated with significant changes in the peak areas of different water states, indicating that increasing FIR temperature was beneficial to hastening water migration. Free water was removed first during drying. At the end of drying, residual moisture in banana samples was dominated by bound water. The images of moisture distribution in banana slices at various FIR temperatures revealed the regulatory mechanism of moisture transfer. Water was gradually lost from the outside to the inside of samples, and high FIR temperatures accelerated dehydration rates. Practical applications Far-infrared radiation (FIR) drying is a high-efficiency modern drying technology with the advantages of high dehydration speed and uniform heating. This study confirmed that FIR drying could significantly reduce dehydration duration compared with traditional hot-air drying. The increase in FIR temperature could expand mass transfer microtunnels, accelerate water migration, and shorten drying time. Therefore, FIR drying is an effective and prospective method for the rapid dehydration of banana slices and other agricultural products.

Research on the pretreatment and mechanical performance of undisturbed phosphogypsum

In this study, dehydration process of original phosphogypsum (PG) was firstly studied by differential thermal analysis method, and the optimal heat treatment temperature was obtained. Subsequently, the effects of dehydration time and ageing time on compressive and flexural strengths of PG pastes were studied. Additionally, the influence of blast furnace slag, silica fume and Portland cement on compressive strength of PG were determined. Results showed that CaSO4·2H2O in PG were dehydrated at three steps and the related dehydration temperatures were 80 ℃, 140 ℃ and 160 ℃. When the dehydration duration at 140 ℃ was 9 h and the ageing time was 5 d the PG paste obtained the best flexural and compressive strength. The addition of blast furnace slag and cement behaved a positive effect on the mechanical strength of PG. The 28 d compressive strength of PG mixture was increased by 97.8 % when the dosage of cement was 40 % by the mass ratio of total binder. Unfortunately, fly ash led to the decreasing mechanical strengths of PG mixture.

Variable extent of dehydration of clinopyroxene megacrysts from Gezi volcano of Inner Mongolia

Mineral phenocrysts/megacrysts convey important information about deep magmatic evolution and volcanic eruption especially with respect to magmatic water content. Clinopyroxene (cpx) is generally considered to be less susceptible to diffusive hydrogen loss than olivine and orthopyroxene. We analyzed hydrogen concentration profiles alongside major and trace element compositions of a suite of cpx megacrysts (1–4 cm in size) hosted in basanitic scoria from the Gezi volcano, central Inner Mongolia of north China. The anhydrous composition within each megacryst is homogeneous, but comparison between different grains shows clear elemental covariation, suggesting that these cpx megacrysts progressively crystallized from a common parental magma. The cpx megacrysts contain hydrogen contents in the range of 0–410 wt ppm H2O at their cores, and some of them show a smooth decrease of hydrogen from the core to the rim. Those with the highest hydrogen contents (290–410 wt ppm H2O) have long plateau at the core, in contrast with long dehydration profiles and no plateau in some low-hydrogen megacrysts. These observations suggest that the cpx megacrysts experienced variable extent of dehydration during volcanic eruption, arising from variable H diffusivity probably associated with differences in the composition and microstructure of cpx megacrysts. Cpx megacrysts with the lowest degree of dehydration and good diffusion profiles are the most informative. Their plateau hydrogen contents at the core are used to infer ~2 wt% H2O in the parental magma. Quantitative modeling of the diffusion profiles at the rim yields a dehydration duration of 3–28 h, suggesting an ascent rate of 1–6 m/s for the host basanitic magma.

A novel rat model of contrast-induced nephropathy based on dehydration

BackgroundContrast-induced nephropathy (CIN) is a frequent cause of hospital-acquired acute kidney injury. Previous animal models developed to explore the pathogenesis of CIN were based primarily on surgery or indomethacin treatment. Thus, we sought to explore a novel CIN rat model comparable to the human CIN. Methods and resultsBoth serum creatinine and tubular injury score were used to assess the successful establishment of the present model. In our study, dehydration duration and the iohexol dosage were found to be the two most important factors to develop a rat CIN model. And, dehydration for 3 days plus furosemide (10 mL/kg) injection before iohexol (15 mL/kg) administration was demonstrated the optimal strategy. Renal injury induced by 15 mL/kg iohexol was almost twice more severe than 10 mL/kg. Moreover, significant renal function decrease, morphological damage and mitochondrial dysfunction occurred as early as 6 h after iohexol injection, not 24 h as previous studies reported. Unexpectedly, we firstly discovered that dehydration after iohexol administration did not increase the extent of renal damage, indicating that hydration after contrast media exposure may be ineffective. ConclusionsA novel CIN rat model based on dehydration and iohexol exposure was established and validated to assist in understanding and preventing CIN.

A proposed mechanism for high pathogen-caused mortality in the seed bank of an invasive annual grass

Abstract Pyrenophora semeniperda can infect nondormant Bromus tectorum seeds under optimal germination conditions, but most escape mortality. This reduces pathogen fitness relative to infection of dormant seeds, which are almost always killed. However, field experiments showed that a large proportion of seeds killed following inoculum addition were not accounted for as dormant seeds, but instead were likely nondormant seeds that would have germinated without inoculum addition. We hypothesized that widely fluctuating water availability to seeds would favor pathogenesis by delaying germination and allowing disease progression at water potentials below those that permit radicle emergence. To test this, nondormant host seeds were inoculated, imbibed for 8 or 24 h, subjected to controlled dehydration for 1–21 d, rehydrated, and scored for mortality. With dehydration at −4 MPa, mortality increased with dehydration duration after short or long imbibition. At −40 MPa, mortality increased with dehydration duration only after long imbibition. At −150 MPa, there was no effect of dehydration duration on generally low mortality. These results illustrate that fluctuating moisture can cause high nondormant seed mortality, explaining how this pathogen kills nondormant seeds.

The Use of Encapsulation-Dehydration Technique for Short-Term Preservation of Endangered Sweet Potato Landraces ( Ipomoea batatas Lam) from Benin

Ex situ conservation of genetic resources remains a challenge for preservation of vegetatively propagated species such as sweet potato. The objective of this study was to establish the protocol based on the encapsulation-dehydration technique for short term preservation of endangered sweet potato landraces produced in Benin. Thus, the evaporative dehydration duration on silicagel was previously determinated on the empty beads which were made using alginate sodium (3%) and calcium chloride (1.32M). Then, the young shoots of two sweet potato landraces (Koidokpon and Dokoui carotte) growing in the screen house were cutted aseptically and desinfected with 10% sodium hypochlorite. The apices were excised on stereoscope and were encapsulated prior their dehydration on silicagel during 5 and 6h. The encapsulated apices were finally conserved in eppendorf tubes at 2°C in batches for 15 days and 90 days. The encapsulated apices were cultured in MS medium supplemented with 0.15 mg/l BAP, 0.2 mg/l NAA, 0.08 mg/l GA3 and 80 mg/l adenine sulfate. The survival and the regeneration rates were then evaluated. At our experimentation condition, the dehydration duration which allowed around 20% water content of the beads was 6h. For the encapsulated apices, the highest survival rates (59.26% and 37.04%) and the highest regeneration rate (37.04% and 11.11%) were recorded respectivelly with the landraces ''Koidokpon'' and ''Dokoui carotte'' when the apices were dehydrated by 6h and stored for 15 days. The regeneration rates decreased according to the stored duration. Significant difference was noted on the regeneration of apices for the landraces tested. This method can be used to preserve the endangered sweet potato landraces and other species during at least three months without subcultures. It also reduce the cost of conservation in terms of consumables and permit better genotype stability during the storage.

EFFECT OF VARIOUS PRECULTURE AND OSMOTIC DEHYDRATION CONDITIONS ON CRYOPRESERVATION EFFICIENCY AND MORPHOGENETIC RESPONSE OF CHRYSANTHEMUM SHOOT TIPS

The aim of this study was to evaluate the influence of sucrose concentration in the preculture medium, as well as the duration of osmotic dehydration on the efficiency of chrysanthemum ‘Richmond’, ‘Lady Orange’ and ‘Lady Salmon’ cryopreservation by encapsulation-dehydration technique. For all cultivars tested, the best regrowth of cryopreserved shot tips was recorded with 0.25 M sucrose concentration and 10&nbsp;µM ABA during a two-week preculture, followed by a 4- or 7-day osmotic dehydration. The survival rate ranged from 56.8–58.0% (the Lady group) to 63.6% (‘Richmond’). However, the ability to grow was smaller and reached 18.2–50.7%. It was found that higher sucrose concentration during the preculture slowed the growth of chrysanthemum shoot tips and led to an increased formation of multiple shoots (by activating axillary buds) or deformed adventitious shoots (incapable of further growth). The frequency of tissue hyperhydricity also increased, while the rhizogenesis efficiency decreased when higher sucrose concentration in the preculture medium was applied. The influence of osmotic dehydration duration on the explants morphogenetic response was cultivar-dependent

Approximate Mathematical Modeling of Osmotic Dehydration of Cone-Shaped Fruits and Vegetables in Hypertonic Solutions

Water loss kinetics in osmotic dehydration of cone-shaped fruits and vegetables was modeled on the basis of diffusion mechanism, using the Fick‘s second law. The model was developed by taking into account the influences of the fruit geometrical characteristics, initial water content of fruit, water diffusion coefficient in fruit, and the water concentration in hypertonic solution. Based on the obtained model, it was shown that the water diffusion coefficient and the initial water concentration of fruit have direct effects on the dehydration rate and also inverse influence on the dehydration duration. The geometrical parameters of fruit and water concentration in hypertonic solution showed direct effect on the dehydration duration as well as inverse effect on the dehydration rate. The presented model seems to be useful tool to predict the dehydration kinetics of cone-shaped fruit during osmotic dehydration process and to optimize the process prior to perform the experiments.

Thin layer drying of wormwood (Artemisia absinthium L.) leaves: dehydration characteristics, rehydration capacity and energy consumption

This study aimed at determining the influence of temperature on drying, rehydration and consumed energy characteristics of common wormwood leaves during thin layer drying. The experiments were carried out at temperatures of 50, 60 and 70 °C and a constant air velocity of 0.7 m s−1. The dehydration duration decreased significantly with increasing drying air temperature. The usefulness of five different mathematical models to simulate the experimental drying kinetics was evaluated and the Midilli model was found to be the best model for explaining the curves. Effective moisture diffusivity values were obtained to be in the range of 7.099 × 10−8–3.191 × 10−7 m2 s−1. Rehydration capacity of the dried leaves increased with increasing rehydration water temperature and decreasing drying air temperature. The specific energy consumption decreased with any increment in drying air temperature and varied from 17.64 to 32.09 kWh kg−1.

Effect of dehydration duration of apices on characteristics of in vitro plants of Fragaria vesca after cryopreservation

Effect of different duration of dehydration of the apices isolated from in vitro plants on genetic stability was investigated in regenerated plants of wild strawberry (Fragaria vesca L., var. alpine) recovered after cryopreservation according to a precultivation-dehydration protocol. Plant material belongs to a clone (cv. Reine des Vallees) that has been maintained in vitro for more than 25 years in Timiryazev Institute of Plant Physiology. It was shown that duration of desiccation the apices before freezing appreciably affected the rate of postcryogenic recovery of plant growth and coefficient of their subsequent propagation. After 5-h-long desiccation, apices were notable for the highest growth rate. The plants restored from such apices also had the highest coefficient of propagation. For DNA analysis, the samples of leaves were taken separately from each plant after hardening and after cryopreservation. According to the results of RAPD, ISSR, and REMAP analyses, the plants from the chosen clone of strawberry showed some genetic variation prior to cryopreservation (percentage of polymorphic fragments was 9.0%). Plant adaptation to cold did not change the level of genetic variation. Among postcryogenic regenerants, morphologically modified plant forms were not observed, with the level of DNA marker variation decreasing almost two times irrespective of the duration of dehydration. However, in one plant restored after 5-h-long dehydration and cryogenic freezing, a 1200 bp fragment of DNA was lacking, which was detected in all other examined samples (frequency of deviation was 0.9%). Earlier, we did not reveal plant polymorphism of investigated strawberry clone associated with this fragment. Probably, this modification of DNA resulted from the exposure of plant material to dehydration and freezing in liquid nitrogen.

Effect of pre-treatment conditions on content and activity of water and colour of freeze-dried pumpkin

This work shows the effect of blanching, osmotic dehydration duration, freezing method and duration of frozen storage on the colour, water activity and water content of osmotically dehydrated and freeze-dried pumpkin. Pumpkin was or was not subjected to blanching process in distilled water at a temperature of 100 °C for 1 min and osmotically dehydrated in starch syrup solution (0, 3 and 20 h) and frozen at −18° (24 h) or −70 °C (2 h). Then, after short (72 h) or long duration (60 days) the pumpkin in frozen storage was freeze-dried on heating shelves at a temperature of 10 °C. Different pre-treatment methods were not found to have clear effect on values of colour coefficient of freeze-dried pumpkin. Osmotic dehydration caused changes in water content and activity of samples. Elongation of osmotic dehydration duration influenced the decrease of water content and activity of freeze-dried pumpkin and had also slight effect on colour changes. Blanching decreased water content and activity, but no significantly. Similar results were obtained also for changes at a temperature of freezing and duration of frozen storage.

Effect of leaf dehydration duration and dehydration degree on PSII photochemical activity of papaya leaves

Although the effect of dehydration on photosynthetic apparatus has been widely studied, the respective effect of dehydration duration and dehydration degree was neglected. This study showed that, when leaves dehydrated in air, the PSII activities of leaves decreased with the decline of leaf relative water content (RWC). Unexpectedly, when leaves dehydrated to same RWC, the decreases in Fv/Fm, Ψo and RC/CSm were lower in leaves dehydrating at 43 °C than those at 25 °C. However, to reach the same RWC, leaves dehydrating at 43 °C experienced 1/6 of the dehydration duration for leaves dehydrating at 25 °C. To distinguish the respective effect of dehydration degree and dehydration duration on photosynthetic apparatus, we studied the PSII activities of leaves treated with different concentration of PEG solutions. Increasing dehydration degree aggravated the decline of Fv/Fm, Ψo and RC/CSm in leaves with the same dehydration duration, while prolonging the dehydration duration also exacerbated the decline of Fv/Fm, Ψo and RC/CSm in leaves with identical dehydration degree. With the same dehydration degree and duration, high temperature enhanced the decrease of Fv/Fm, Ψo and RC/CSm in the leaves. When leaves dehydrated in air, the effect of high temperature was underestimated due to reduction of dehydration duration. The results demonstrated that, dehydration degree and duration both play important roles in damage to photosynthetic apparatus. We suggest that, under combined stresses, the effects of dehydration degree and duration on plants should be considered comprehensively, otherwise, partial or incorrect results may be obtained.

Influence of motion parameters of the drying agent on kinetics of mixed heat transfer drying

The paper deals with studying the influence of motion parameters of the drying agent on the kinetics of mixed heat transfer drying for obtaining the requirements to functional features of turbulators, used in drying by this method.It was noted that one of the promising drying methods in terms of increasing the dehydration intensity, reducing specific energy consumption per unit of dried products and preserving the feedstock quality is mixed heat transfer drying.Installation for studying the influence of motion parameters of the drying agent on the temperature kinetics and the moisture content kinetics of feedstock during MHT-drying was designed and built. Based on studies of temperature kinetics and moisture content kinetics of feedstock at different angles of blowing of mass transfer gaps by drying agent from the range 0°–90° it was found that the temperature kinetics of feedstock at the investigated blowing angles are of nature, typical for the MHT-process. It was determined that the dehydration duration is the longest for blowing angles 25°–35°, time the thermogram achieves local minimum and, respectively, maximum of drying speed for this range is the latest. It was found that at increasing and decreasing the blowing angle with respect to this range, drying duration reduces and maximum dehydration speed is reached earlier. It is noted that inserts-turbulators, which are structural features of MHTdryers, must provide blowing of FC mass transfer gaps by drying agent at angles, close to rational, which are the angles 0° and 60°.