Open AccessExperimental researches on vegetable assimilation and respiration V.—A critical examination of Sachs’ method for using increase of dry weight as a measure of carbon dioxide assimilation in leaves
Author(s) -
D. Thoday
Publication year - 1909
Publication title -
proceedings of the royal society of london. series b, containing papers of a biological character
Language(s) - English
Resource type - Journals
eISSN - 2053-9185
pISSN - 0950-1193
DOI - 10.1098/rspb.1909.0054
Subject(s) - assimilation (phonology) , carbon dioxide , photosynthesis , dry weight , chemistry , trustworthiness , carbon assimilation , measure (data warehouse) , mathematics , botany , environmental science , biology , computer science , biochemistry , philosophy , linguistics , computer security , organic chemistry , database
The trustworthiness of Sachs’ well-known dry-weight method for measuring the rate of accumulation and translocation of the products of photosynthesis in leaves was called in question in1905 by Brown and Escombe. In their paper “On the Physiological Processes of Green Leaves,” they published an account of four experiments in which they had determined for the same individual leaves both the increase of dry weight, by Sachs’ method, and the amount of carbon dioxide actually absorbed, by their own method. They sum up the results by saying : “If we take the mean of all four experiments we find that the Sachs method gives an estimate of the assimilation rate between two and three times greater than that deduced from the intake of carbon dioxide.” In attempting to explain this discrepancy they made some determinations of the degree of symmetry existing between opposite sides of various leaves, and of the amount by which half-leaves changes in area under experimental conditions. They concluded from these that the errors to which the method is liable are of the same order of magnitude as the quantities to be measured, and that therefore “the Sachs method cannot be trusted for anything like exact quantitative estimation leaf. As ordinarily applied, its general tendency is to give far too high an estimate of the rate of assimilation.”