CHAPTER 2 



EXPERIMENTAL MATERIALS 

 AND METHODS 



The methods in physiology are in no respect different 

 from those employed in other sciences, and thus in 

 order to obtain a sufficiently broad comprehension 

 of the phenomena observed, and to permit the 

 establishment of general laws, it is essential that a 

 comparative study of a great variety of plants should 

 be made. 

 W. Pfeffer. The Physiology of Plants (1900) 



A. Experimental Materials 



1. Intact Angiosperms 



Salt absorption has been studied in a wide variety of botanical 

 materials, ranging from intact angiosperms rooted in soil to sub- 

 cellular organelles. The earliest investigations were conducted upon 

 whole vascular plants growing under natural conditions, but now- 

 adays most plant physiologists have abandoned soil to the soil 

 scientists, and have chosen to concentrate their efforts on elucidating 

 the lesser (but still considerable) complexities presented by plants 

 growing in solution culture. Many have taken a step further and 

 regard an intact angiosperm as too complicated a system for useful 

 investigation. Instead, isolated parts of plants are used as experi- 

 mental material, with the ultimate objective of building up an 

 integrated picture of salt absorption and transport in the whole 

 organism. Much can be learned about the mechanism of ion 

 movements at the cell level by the study of homogenous tissues, but 

 the relevance of such knowledge to the processes going on in the 

 intact plant must ultimately be demonstrated rather than assumed. 



2. Excised Roots 



Many investigators have favoured the use of excised roots in the 



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