i88 
W. H. Pearsall and J. H. Priestley 
and at its iso-electric point the protein will most readily part with 
water if in contact with other systems which tend to absorb water. 
Now in the case of a vacuolated cell the cytoplasm of the cell 
may be considered to retain water as a result of the swelling properties 
of its proteins. Suppose we take the case of a series of such cells 
lying along a gradient of hydrogen-ion concentration. 
If somewhere along the gradient lies the iso-electric point of one 
of the main constituent cell proteins, then at this point there will be 
a distinct tendency for the cytoplasm to lose water to cells on either 
side, which are at different hydrogen-ion concentrations and therefore 
have greater affinity for water. Under these circumstances, the 
gradual accumulation within such cells of a dense, unvacuolated, or 
only slightly vacuolated, mass of protoplasm whbse water is lost to 
neighbouring cells is at least conceivable. Furthermore, such a 
tendency to water loss would produce a definite tendency towards 
synthesis, rather than towards hydrolysis. The characteristic meta¬ 
bolic processes in plants are condensations in one direction, involving 
the elimination of water, and hydrolyses in the other direction, 
involving the addition of water. We may, for example, visualise the 
particular case of protein synthesis as being essentially the union of 
two anyno-acids or their complex derivatives, A and B, to form 
the more complex substance, C, and water, e.g. 
A +B^±C + H 2 0 . 
Now according to the law of mass action, the concentrations of 
these four substances are proportional to one another (cf. Bayliss, 
2, p. 239) as follows: 
(cone. C) (cone. H 2 0 ) 
(cone. A) (cone. B) 
= a constant. 
From this general equation it is clear that in order to increase the 
concentration of C the concentration of water must be reduced. In 
other words, starting from a given point, elimination of water will 
lead to synthesis of C, addition of water will lead to hydrolysis of 
C, until a new equilibrium is attained. From this point of view 
elimination of water appears to be an essential condition for synthesis 
in plant meristems. 
Our test-tube knowledge of protein synthesis enables us only to 
envisage such condensation by analogy, but the extensive series of 
carbohydrate syntheses and of carbohydrate ester syntheses by the 
use of enzymes in alcoholic media with low percentages of water 
(Bourquelot and Bridel(3)) supply strong evidence in support of 
