4 THE FIELD OF PLANT PHYSIOLOGY 



Plant Physiology as a Science. — The origin of man's first conscious 

 interest in plants long antedates recorded history. Agriculture had already 

 become a highly developed art thousands of years before any experimental 

 study of plant processes began. Consequently, there had grown up a vast body 

 of traditional plant lore v^^hich passed orally from father to son, generation 

 after generation. This practical know^ledge of plants developed over many 

 centuries as a result of countless, mostly involuntary trial and error experiences 

 and innumerable observations of plant behavior under all kinds of circum- 

 stances. IVIuch of this mass of mingled facts and beliefs regarding plants is 

 alive in the consciousness of the common man today. The closer he lives to 

 the soil and the more familiar he is with traditional plant lore, the more it 

 influences his thoughts and actions. 



Many of these customarily accepted beliefs are essentially sound and most 

 of them contain elements of truth. Others, however, are entirely erroneous, 

 and not a few are tempered with superstitions, some of which have an unbroken 

 lineage back to the days of witch-doctors and savagery. No reputable botanist 

 has held for generations, for example, that plants obtain their food from the 

 soil, yet this and many other fallacious beliefs are still widely entertained 

 among the general population. 



The value of practical information about plants should not be underrated, 

 since its perpetuation in the mind of man permitted the development of 

 agriculture to a high plane as a practical art before any widespread investiga- 

 tion of plants from a scientific point of view was undertaken. Nevertheless, 

 traditional plant lore is not only often inadequate, but is riddled with mis- 

 conceptions, and often suffers from points of view which are inherently stulti- 

 fying to the acquisition of further knowledge. 



The layman, for example, often personifies plants in an attempt to explain 

 their behavior. Man has desires and foresight and it is often assumed, either 

 consciously or tacitly, that plants are similarly endowed. To many, for ex- 

 ample, the statement that "roots grow downwards in search of water," or that 

 "stems grow upwards in order to reach the light" are accepted as adequate 

 "explanations" of plant behavior. Man's knowledge that water and light are 

 essential to plants is not evidence that plants are similarly aware of these facts. 

 To assume that plants realize their needs and are able to act in conformity 

 with their requirements is equivalent to crediting them with a high order of 

 intelligence. Explanations of plant behavior are commonly encountered in 

 which purposeful action on the part of plants is tacitly or deliberately implied, 

 although there is no justification for the adoption of such a point of view. 



Furthermore, the layman seldom pursues his quest for information about 

 plants beyond the stage of observation, while the scientist frequently does. 



