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

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8.1 Sorption from Aqueous Solutions 235 ln Partition coefficient ln Partition coefficient 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 12 −5 −4 −3 −2 −1 0 1 log Internal concentration (mol/kg) 6.0 5.5 5.0 4.5 4.0 3.5 3.0 5 15 °C 30 50 °C 5 20 35 Internal concentration (g/kg) 0.014 0.139 1.39 13.9 139 Internal concentration (g/kg) Lycopersicon 0.014 0.139 1.39 13.9 139 2.5 12 −5 −4 −3 −2 −1 0 1 log Internal concentration (mol/kg) Ficus Fig. 8.1 Partition coefficients of 4-nitrophenol for CM (red) and MX (blue) from Lycopersicon esculentum fruits and Ficus decora leaves as functions of temperature and concentration of sorbed solute. (Redrawn from data of Riederer and Schönherr 1986a) 403 245 148 90 55 33 20 403 245 148 90 55 33 20 Partition coefficient Partition coefficient
236 8 Effects of Temperature on Sorption and Diffusion of Solutes and Penetration of Water while the CM also contains waxes as additional lipid component. As shown in Sect. 6.1, wax/water partition coefficients are much smaller than cutin/water partition coefficients. Thus, cutin is the sole sorbent in the MX and the major sorbent in CM. Partition coefficients decrease with increasing temperature and increasing internal solute concentration. Between 10 −4 and 10 −2 mol kg −1 or 1.39 and 0.014g kg −1 , internal concentrations of partition coefficient were nearly constant, but at higher internal concentrations K decreased. This decrease is more pronounced in rubber than in tomato CM and MX. With rubber CM and MX, all sorption plots converge at an internal concentration of about 1mol kg −1 . This indicates that all sorption sites are occupied and additional sorption is no longer possible. With tomato fruit cuticles, partition coefficients also decrease at higher 4-NP concentrations but plots do not converge. The difference in internal concentrations between CM and MX is highest at low sorbate concentrations, but it decreases as concentration increases. If waxes sorb little or no 4-NP, partition coefficients for MX would be expected to be higher by 8% and 25% with tomato and rubber cuticles respectively. However, differences are larger, indicating that in MX some sorption sites are occupied by waxes. At low external concentration of 4-NP, partition coefficients were nearly constant, even though internal 4-NP concentration increased 100-fold. This indicates that additional new sorption sites become available when others are being occupied by 4-NP molecules. The flexible polymer chains open up, and sorbate molecules squeeze in between. There is a limit to this, however, and when internal concentration exceeds 10 −2 mol kg −1 additional sorption sites are no longer formed and partition coefficients decrease. Partition coefficients decrease much more with rubber leaf cuticles, indicating that flexibility of polymer chains is smaller compared to tomato fruit cuticles. It appears that cutan in rubber leaf cuticle is more rigid and provides fewer sorption sites. The temperature effect on partition coefficients depends on the temperature effect on activities of the two phases. With substituted phenols, partition coefficients between inert organic phases which are incapable of hydrogen bonding increase with temperature, while octanol/water partition coefficients decrease with increasing temperature (Korenman et al. 1977). Cuticle/water partition coefficients also decreased with increasing temperature, and this is evidence that hydrogen bonding between cutin and 4-NP was involved in sorption. The temperature effect on sorption can be further analysed using a modified Freundlich isotherm. This makes it possible to distinguish between temperature effects on the number of sorption sites (solubility in cuticles) and on water solubility. Cinternal = k ′ ·(Caqueous/C saturated aqueous ) 1/n (8.2) The term in parenthesis is referred to as the reduced concentration. Plotting log Cinternal vs log of the reduced concentration resulted in straight lines with slopes k ′ . With Ficus CM and MX, k decreased with increasing temperature (8.1), while k ′ was independent of temperature (8.2). Hence, the temperature effect on Ficus
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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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Page 194 and 195: 184 6 Diffusion of Non-Electrolytes
Page 216 and 217: 206 7 Accelerators Increase Solute
Page 242 and 243: Chapter 8 Effects of Temperature on
Page 246 and 247: 8.1 Sorption from Aqueous Solutions
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Page 256 and 257: 8.3 Water Permeability in CM and MX
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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 278 and 279: 9.8 Measuring Solute Permeability 2
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
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References 287 Doty PM, Aiken WH, M
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References 289 Kolattukudy P (2004)
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References 291 Sabljic A, Güsten H
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References 293 Schreiber L, Schönh
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Index 2,4-D, 46 2,4-Dichlorophenoxy
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Index 297 leaf disks, 130 leaf surf
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Index 299 water molar volume, 110 p
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