THE UPWARD TRANSLOCATION OF FOODS IN WOODY PLANTS 293 
Discussion 
The available data are not sufficiently extensive to enable one to con- 
clude from how far back food is withdrawn to be used in shoot growth. 
It is probable that the amount of upward movement depends upon the kind 
of tree, its age, and conditions of previous growth, as well as on conditions 
during the current season. 
Leclerc du Sablon suggested that some trees may store but little of their 
food in the roots, while others store quantities there to be used later in 
shoot growth, but his experiments supposedly proving the latter condition 
are far from convincing. It is to be noted that he used young trees only 
three to four years old, and, though his data offer no conclusive proof, it is 
possible that such young trees might show more upward transfer of foods; 
but it is just as possible that, when a tree becomes well established, there 
is normally very little upward translocation. Other conditions being equal, 
one would expect little or no withdrawal of carbohydrates from below if 
during the spring growing season there were a deficiency of water and per- 
haps of mineral nutrients, especially nitrates, and the days were bright. 
Under such conditions vegetative growth would tend to become checked 
early, and the new leaves would soon begin to accumulate carbohydrates 
through photosynthesis. 
If root growth commenced in the spring before shoot growth, or even 
if growth began in both at about the same time, one would expect that most 
of the food present in the roots would be immediately needed by the roots. 
No very conclusive evidence on this point is available, but Goff (1898) 
found that root growth may commonly precede the swelling of buds. 
Observations were made by digging trenches early in the spring and meas- 
uring the amount of new growth that had occurred up to the time of digging. 
Such early root growth was found to occur in the following plants: Acer 
saccharum, Pyrus malus, Pyrus communis, Prunus cerasus, Prunus vir- 
giniana, Betula alba, Moms alba, Cornus stolonifera, Eleagnus hortensis 
var. Songorica, Ribes rubrum, Ribes nigrum, Ribes oxyacanthoides ; as well 
as in nine species of gymnosperms and a few herbaceous perennials. There 
were only two possible exceptions recorded. 
Furthermore, data presented by Jones (1903) would indicate that root 
growth precedes stem growth. It was found that the water content of 
the trunk of the sugar maple increased from 31.5 percent in December to 
36.5 percent in March, while from March 15 to April 28 the water content 
increased to 47 per cent. After this date the buds opened and the water 
content fell off. This rapid increase in water content just previous to the 
opening of the buds, which occurs not only in the maple but in all the other 
deciduous trees examined, though it cannot be considered as conclusive 
proof, yet at least suggests that the absorbing organs, the roots, have 
started growth early, making possible a rapid absorption of water just 
previous to shoot growth. 
