THE EFFECT OF RINGING A STEM ON THE UPWARD 
TRANSFER OF NITROGEN AND ASH CONSTITUENTS 
Otis F. Curtis 
(Received for publication October 23, 1922) 
From a variety of experiments conducted to determine the effect of 
ringing on the upward transfer of carbohydrates (Curtis, 1920), evidence 
was obtained indicating that these foods are carried up the stem chiefly 
through the phloem tissues even though much of the food to be transported 
is present as sugar or starch in the xylem tissues. At least the upward 
transfer of sugars seems to be very clearly checked by the removal of a 
ring of phloem. When it was realized that sugar may be present in the 
vessels of the xylem at the time water is being carried in these tissues and 
yet may not be carried past a region where a ring of phloem is removed, 
the question immediately presented itself as to whether the commonly 
accepted idea that nutrients are carried in the “transpiration stream” is 
a correct one. 
Though the literature is full of statements to the effect that inorganic 
materials absorbed from the soil are carried through the xylem in the 
“transpiration stream,” these for the most part are based on mere assump¬ 
tion or on evidence which is far from conclusive. Certain facts have com¬ 
monly been offered as proof of rapid transfer in the “transpiration stream.” 
One of the commonest of these is that salts are dissolved in the soil water, 
and, as the water is known to be carried more or less rapidly through the 
xylem to the transpiring tissues, at first thought it would seem perfectly 
logical that the nutrients dissolved in the water would be absorbed and 
carried with it. If this were true, it would readily account for the rapid 
absorption and distribution of salts, but since the movement of water and 
that of solutes through osmotic membranes may be independent of each other, 
the salts are not necessarily carried with the water. Evidence showing 
that there is no direct relation between water absorption and salt absorp¬ 
tion has been presented in the work of Muenscher (1922) and others. 
Whether or not the movement of water after absorption influences the 
transfer of solutes depends in part on whether the solutes get into the 
water-conducting tissues, and in part on whether these tissues form con¬ 
tinuous open tubes with few or no obstructions. It would also depend on 
the method of water movement, that is, whether the movement is by 
mass flow throughout, or by diffusion throughout, or, as is perhaps more 
probable, by mass flow through certain regions and diffusion through 
others. The possible presence of associated parenchymatous cells, with- 
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