•202 



A QUANTITATIVE ANALYSIS OF PLANT GROWTH 



TART II. 



By G. E. BRIGGS, M.A. (Cantab.), 

 FRANKLIN KIDD, M.A. (Cantab.), D.Sc. (Lond.), 



AND 



CYRIL WEST, A.R.C.Sa, D.Sc. (Lond). 

 (With 6 text-figures.) 



PAGE 



I. Unit Leaf Rate 202 



II. Correlation of Unit Leaf Rate with Environmental Factors . . 208 



III. Correlation of Real Assimilation with Environmental Factors . . 214 



IV. A Comparison of Assimilation Values determined by the "Growth" 

 Method with those determined by "Gasometric" and '•' Half-Leaf" 

 Methods 217 



V. Summary 220 



CHAPTER II. 



I. Unit Leaf Rate. 



In the previous chapter we showed that the Relative Growth Rate curve, 

 that is, the weekly percentage increase in dry-weight plotted against 

 time, for such a plant as maize, has the general form shown in Fig. 1, 

 curve A. Secondly, it was found that the Leaf- Area Ratio curve, that 

 is, the leaf-area per unit dry-weight plotted against time, has the same 

 general form, Fig. 1, curve B. This similarity in the form of the two 

 curves suggests that the weekly increase in dry- weight per unit leaf-area 

 is more or less constant throughout the life-cycle of the plant. In order 

 to ascertain how far this is true we have dealt with the results of 

 Kreusler(i3, 14, is, lo), wiiich were quoted at length in the previous 

 chapter (5), by calculating the values for what we propose to call the 

 Unit Leaf Rate and presenting them for the complete life-cycle of the 

 plant in Unit Leaf Rate curves (Tables I— IV and Figs. 3-6). The Unit 

 Leaf Rate in this paper is the increase in dry-weight per square centi- 



