692 F. C. STEWARD AND R. G. S. BIDWELL 
linked to an understanding of the organization of the cell, the organ and the organism. 
This requires investigation by methods that take account of these complexities of 
the problem. While for many features of the individual reactions one must seek the 
simpler and more homogeneous systems, the work should not rest there, for this will 
not solve the problem of amino acid and protein metabolism of higher plants; it will 
merely evade many of them that are dependent upon the organization of cells and 
of the entire plant body. In this context the changes in nitrogenous compounds of 
higher plants that may be induced by such variables as photo- and thermo-period, 
as illustrated by the mint plant*®, are very much concerned with the effect of the 
variables in question, and their interaction, on the organized plant body. Similarly, 
the dramatic effects of growth induction upon the synthesis and turnover of protein 
in cells in culture should be thought of in relation to the equally dramatic and visible 
changes in the cells as they pass from the resting to the actively growing state (cf. 
STEWARD#!, Fig. 3, p. 452) for the comparison of carrot, potato and banana cells at 
rest in the intact organ and as they appear when in active growth in the free state). 
It is to explain such situations that one needs to invoke the concepts that have been 
developed in this paper. 
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