PREFACE 



It is a striking illustration of the current world-wide interest in the 

 investigation of plant water relations that it should have been possible 

 for the British Ecological Society to organize a symposium, on this topic 

 in 1961, barely two years after a similar one had been held in Madrid, 

 under the auspices of Unesco*, and that a different set of contributors 

 of international reputation should have been available to sustain the 

 symposium. It is true that the Madrid symposium was mainly con- 

 cerned with the problems of arid lands, and this volume is to an extent 

 complementary in that it lays greater emphasis on temperate vegeta- 

 tion. The authors of the Reviews of Researchf which preceded the 

 Madrid symposium, performed a most valuable task in giving a syste- 

 matic account of the soil-plant-air system through wliich water moves 

 and the relation of the physiology and growth of plants to the water 

 factor. But already it has become possible to add, in this volume, new 

 information on subjects of fundamental importance to plant water 

 relations, such as evaporation, dew formation and water movement 

 through soil and plant. In addition investigations from very varied 

 standpoints of the relationship of water balance to growth and develop- 

 ment represent a valuable contribution to the understanding of the bio- 

 logical problems involved. 



As a result of some late withdrawals of papers, matched by some 

 fortunate late contributions, the plan of arrangement of topics in the 

 symposium was somewhat disturbed, and in preparing the proceedings 

 for pubhcation the opportunity has been taken to re-arrange the contri- 

 butions in a more logical order. 



The first section on Water in the Environment contains papers from 

 both geographical and physical points of view. It is followed by two 

 studies of water in the plant, one of which presents new evidence on the 

 path of water movement while the other critically re-examines a tech- 

 nique, the determination of leaf water deficit (or relative turgidity, its 



* UNESCO, Arid Zone Research Series, No. 16, 1961. 

 t Ibid, No. 15, i960. 



ix 



