C H A P T E R V
A NEW APPROACH TO THE WATER RELATIONS
OF DESERT PLANTS
H. Walter and E. Stadelmann
I. Introduction
214
II. Rainfall and Water Supply of Desert Plants
214
III. "Diffuse" and "Contracted" Vegetation
218
IV. The Significance of Soil Texture for the Water Supply öf Desert
Plants
219
V. Distinctive Features of Deserts
223
VI. Hydration of Protoplasm and Osmotic Potential
225
VII. Plant Hydrature and Environmental Water Conditions
229
VIII. Diurnal Fluctuation of the Osmotic Potential (ψ 8 )
234
IX. Annual Variations of the Osmotic Potential (ψ 8 )
237
X. The Ecological Types of Desert Plants
238
XI. Osmotic Quantities and Importance of Hydrature for Growth and
Xeromorphism
242
XII. Osmotic Potential {ψ 8 ), Growth, and Production of Organic Matter. . . 249
XIII. The Relation between the Osmotic Potential {ψ 8 ) and the Anatomical
and Morphological Characteristics of Plants
255
A. Encelia farinosa
255
B. Other Heterophyllic Plants
257
C. Cactaceae
257
XIV. The Ecological Plant Types in Arid Regions
262
XV. Hydrature in True Xerophytes
263
A. Poikilohydric Xerophytes
264
B. Malacophyllous Xerophytes
266
C. Sclerophyllous and Aphyllous Xerophytes
266
D. Stenohydric Xerophytes
268
XVI. The Hydrature of Succulents
270
XVII. Saline Soils in Arid Regions
274
XVIII. Halophytes and Salt Uptake
279
XIX. The Effects of Ions on Protoplasm
281
XX. Chloride Accumulation in Halophytes
285
XXI. Types of Halophytes
292
References
302
213