July 22, 1918 
Salt Requirements for Buckwheat Plants 
173 
A comparison of the water requirement diagram for seeds with the 
corresponding yield diagram indicates a very close agreement between 
the areas representing high water requirement and those of low yields. 
The areas of low water requirement values correspond also, in a general 
way, with the areas of high yields. 
From the above observations it is clear that a fairly definite relation 
exists between the dry-weight yields and water requirements for each 
of the two series of buckwheat plants here considered. This relation 
may briefly be stated as follows: In general, high yields of tops, roots, 
and seeds correspond to low water requirements, and low yields corre¬ 
spond to high water requirements. It is thus to be expected that 
favorable conditions for the growth of these plants are associated with 
relatively low water requirements, while unfavorable conditions for 
growth will demand a relatively larger amount of water to produce 1 
gm. of dry plant substance. 
A comparison of the water-requirement diagrams of series A with 
the corresponding diagrams of series B brings out the fact that there 
is no similarity between the diagrams of the two series representing the 
two developmental growth periods with respect to the positions and 
distribution of the areas of high and low water requirement values. 
Thus there is a marked difference in the manner in which the water- 
requirement values of the two series vary with respect to the variations 
in the salt proportions of the solutions employed. 
From the preceding considerations of the various plant measurements 
it is at once clear that the relation of the growth rate of the buckwheat 
plants to the proportions of the three salts in the solutions here em¬ 
ployed is markedly different for the early and late developmental 
periods represented by series A and series B, whether this relation is 
judged by the criterion of dry weights of tops or of roots, by that of 
transpiration, or by that of water requirements of tops or of roots. 
It is to be emphasized, of course, that the changes in the physiological 
requirements of these plants, with respect to the salt proportions, may 
be a gradual process extending over a comparatively long time period. 
Such a change might even begin soon after germination of the seed and 
continue during the entire active growth period of the plants. If, 
therefore, the entire growth period should be divided into a larger num¬ 
ber of partial periods than the two which have here been considered, 
and the best physiological balance of salt proportions determined for 
each, these partial periods might possibly call for other salt proportions 
for the production of maximum yields than the ones which gave the 
highest yields during the first or during the last 4-week period of 
these tests. On the other hand, the change in the salt requirements of 
the plants may take place comparatively rapidly with the marked 
changes which occur within the plants during the period of blossoming, 
when the vegetative processes become less active and the reproductive 
and seed-forming processes begin. 
