Water and Solute Permeability of Plant Cuticles: Measurement and ...

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9.8 Measuring Solute Permeability 269 Sects. 6.1 and 9.5. During our studies of permeability of plant cuticles, a number of new methods have been developed, some which proved useful and are summarised here. Further details not mentioned in Chaps. 1–8 are also provided. Mass flow can be studied either in the steady (Sect. 6.2.1) or in the transient state (Sect. 6.3). Detached leaves or conifer needles can be studied using the submersion technique (Sect. 6.2.2). The well technique is more convenient with leaf disks from broad-leaved plants (Sect. 6.2.3). Merits and drawbacks associated with the above methods are discussed in Chap. 6, and need not be repeated here. Our analysis of barrier properties of cuticles draws heavily on data collected using isolated cuticular membranes (CM). This makes it possible to measure penetration in the transient state (Sects. 2.5, 6.3 and 6.4). Solute mobility in the limiting skin and in the sorption compartment of the CM can also be studied quantitatively. These methods are very powerful for analysing the reasons for differences in permeability among species and solutes (Sect. 6.3.2). The role of accelerators (plasticisers) in cuticular penetration also relies on these methods (Chap. 7). This warrants a closer look at these new methods. All of them rely on radio-labelled solutes. The CM are equilibrated with an aqueous solution containing the radio-labelled solute. Solutions must be buffered if the solute is a weak acid or base. After equilibration most solutes are contained in the sorption compartment, which has also the largest mass (Sect. 1.4). The limiting skin is very thin, and only a small percentage of the total amount sorbed is located there (Fig. 9.5). Solutes sorbed in the CM can be desorbed using an apparatus shown in Fig. 9.4. For simultaneous bilateral desorption (BIDE) the CM is inserted into the apparatus, and the two compartments are filled with the desorption medium (water, buffer or phospholipid suspension, depending on properties of solute). The receiver solutions are withdrawn periodically and exchanged for fresh ones. Radioactivity of receiver solutions is determined by scintillation counting. Typical results are shown in Fig. 6.15. From the desorption kinetic, the average rate constants (6.13) and diffusion coefficients in the limiting skin and the sorption compartment can be estimated [(2.33) and (2.35)]. Desorption from the inner surface is very rapid, and samples must be taken in very short intervals. If desorption media are added only to the half-cell facing the morphological inner surface of the CM, the process is called unilateral desorption from the inner surface (UDIS). Diffusion of solutes into the sorption compartment (soco) of the CM is very rapid,and sampling intervals of 1–3 min are necessary to estimate diffusion coefficients from the initial rates of desorption (Fig. 6.20). These methods are depicted schematically in Fig. 9.5. Solute mobility in the limiting skin is measured using unilateral desorption from the outer surface (UDOS). A simpler method of loading the CM with solutes is used. The CM are inserted in a simple apparatus (shown in Fig. 6.17). A droplet (200µl) of aqueous donor solution is added to the inner surface of the CM exposed in the orifice of the cover and allowed to dry. During evaporation of water at ambient temperature and humidity, the solute is driven into the sorption compartment of the CM, as solute concentration in the droplet increases during evaporation of water. An experiment with 14 C-labelled solute and THO showed that the ratio 14 C/ 3 H
270 9 General Methods, Sources of Errors, and Limitations in Data Analysis Fig. 9.4 Apparatus made of stainless steel used for unilateral or bilateral desorption (UDIS or UDOS). The CM (yellow) loaded with radio-labelled solute is inserted between the two halves of the apparatus, desorption media are added through the sampling ports and solutions are stirred for mixing. Desorption media are withdrawn periodically and fresh ones are added. The apparatus in maintained at constant temperature
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Water and Solute Permeability of Pl
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Professor Dr. Lukas Schreiber Ecoph
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vi Preface This is not a review abo
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Contents 1 Chemistry and Structure
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Contents xi 4.6.3 Diffusion Coeffic
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Contents xiii 7.4.2 Effects of Plas
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2 1 Chemistry and Structure of Cuti
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10 1 Chemistry and Structure of Cut
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Chapter 2 Quantitative Description
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2.1 Models for Analysing Mass Trans
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2.3 Steady State Diffusion Across a
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2.4 Steady State Diffusion of a Sol
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2.4 Steady State Diffusion of a Sol
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2.5 Diffusion Across a Membrane wit
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2.5 Diffusion Across a Membrane wit
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2.6 Determination of the Diffusion
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Solutions 51 2.7 Summary In this ch
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Chapter 3 Permeance, Diffusion and
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3.1 Units of Permeability 55 3.1.1
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3.1 Units of Permeability 57 identi
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3.3 Partition Coefficients 59 The d
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Chapter 4 Water Permeability All te
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4.1 Water Permeability of Synthetic
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4.2 Isoelectric Points of Polymer M
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4.2 Isoelectric Points of Polymer M
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4.3 Ion Exchange Capacity 69 The hi
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4.3 Ion Exchange Capacity 71 has an
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4.3 Ion Exchange Capacity 73 Counte
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4.4 Water Vapour Sorption and Perme
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4.4 Water Vapour Sorption and Perme
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4.5 Diffusion and Viscous Transport
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4.6 Water Permeability of Isolated
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Problems 121 Our present knowledge
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Solutions 123 5. Ca 2+ , because se
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126 5 Penetration of Ionic Solutes
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146 6 Diffusion of Non-Electrolytes
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206 7 Accelerators Increase Solute
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Page 244 and 245: 8.1 Sorption from Aqueous Solutions
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Page 248 and 249: 8.2 Solute Mobility in Cuticles 239
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Page 258 and 259: 8.3 Water Permeability in CM and MX
Page 260 and 261: 8.4 Thermal Expansion of CM, MX, Cu
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Page 266 and 267: Problems 257 E D (kJ/mol) DH S (kJ/
Page 268 and 269: Chapter 9 General Methods, Sources
Page 270 and 271: 9.2 Testing Integrity of Isolated C
Page 272 and 273: 9.4 Distribution of Water and Solut
Page 274 and 275: 9.6 Cutin and Wax Analysis and Prep
Page 276 and 277: 9.7 Measuring Water Permeability 26
Page 280 and 281: 9.8 Measuring Solute Permeability 2
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Page 284 and 285: 276 Appendix A Abbreviations (conti
Page 286 and 287: 278 Appendix A Symbols (continued)
Page 288 and 289: 280 Appendix B Physico-chemical pro
Page 290 and 291: Appendix C Index of Plants Botanica
Page 292 and 293: References Abraham MH, McGowan JC (
Page 294 and 295: References 287 Doty PM, Aiken WH, M
Page 296 and 297: References 289 Kolattukudy P (2004)
Page 298 and 299: References 291 Sabljic A, Güsten H
Page 300 and 301: References 293 Schreiber L, Schönh
Page 302 and 303: Index 2,4-D, 46 2,4-Dichlorophenoxy
Page 304 and 305: Index 297 leaf disks, 130 leaf surf
Page 306: Index 299 water molar volume, 110 p
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