EFFECT OF DIFFERENT RATES OF TRANSPIRATION 
ON THE DRY WEIGHT AND ASH CONTENT OF THE 
TOBACCO PLANT? 
By Nemesio B. MENDIOLA 
Of the Department of Agronomy, University of the Philippines, and of the 
Bureau of Agriculture 
REVIEW OF PREVIOUS WORK 
Authorities are divided in their views regarding the relation- 
ship between the rate of transpiration of a plant and the intake 
of soil solutes. On the one hand it is held that the amount of 
solute taken up by the plant from the soil solution is proportional 
to the amount of water transpired, while on the other the 
amount of solute taken in by the plant is believed to be inde- 
pendent of the amount of water transpired. The available 
experimental data relating to this question are few. 
As early as 1849 Lawes,(1) while realizing the relationship 
of evaporation to rapidity of growth to be yet a problem, never- 
theless assumed generally that the comparative rate of evapor- 
ation of water to some extent indicates the comparative activity 
of the processes of the plants. In his experiments with wheat, 
barley, beans, peas, and clover, in which he determined the 
amount of water given off by the plants and the amount of dry 
matter and ash obtained from them, he got a greater amount 
of dry matter and ash with a greater amount of water, and 
vice versa. It should be remarked, however, that the plants 
were not given the same soil treatments. He merely concluded 
that these experiments indicated some definite relationship be- 
tween the passage of water through the plants and the fixation 
in them of some of their constituents. 
Schloesing, (2) in 1869, grew one tobacco plant under a shaded 
bell jar and three in the open. The water evaporated per plant 
in the open averaged more than three times that evaporated 
* A report on the research problem presented in 1917 to the department 
of botany, Cornell University, to satisfy in part the requirements for a 
minor in plant physiology. 639 
