50 



EIGHTEENTH REPORT. 



THE INFLUENCE OF AN INCOMPLETE CULTURE SOLU- 

 TION ON PHOTOSYNTHESIS. 



(Abstract.) 



BY O. M. GRUZIT AND R. P. HIBBARD. 



We are far from possessing a precise knowledge of the role of 

 the various mineral elements in plant life. They do not afford a 

 source of energy like the organic compounds, carbohydrates, fats 

 and proteids. There is much evidence to show that they are es- 

 sential to the protoplasmic molecule and to regulate other chemical 

 and physical conditions, which are at present so little understood. 



We do know, however, that normal development is interfered 

 with and in some cases inhibited when one or more elements are 

 lacking in the culture solution. The studies reported in this paper 

 were planned to determine, if possible what influence an incom- 

 plete culture solution exercises on the various, so-called vital ac- 

 tivities of the plant, and more especially upon the photosynthetic 

 process. The following table gives the amount of photosynthate 

 made per ghm2 in the different solutions. 



TABLE I. 



Culture Solution 



Complete 



Distilled Water 



Tap Water 



Iron Omitted 



Phosphorous Omitted . 



Nitrogen Omitted 



Potassium Omitteii , . . 

 Magnesium Omitted /. 



Calcium Omitted 



Sulphur Omitted 



Gain in dry 



weight per 

 ghm2. 



Exp. No. 1. 

 0. 1.5.57 gms. 

 . 2207 gms. 

 . 2045 gms. 

 . 2207 gms. 

 0.3380 gms. 



0.1647 gms. 

 *0.0724 gms. 



0.2607 gms. 



0.3128 Kms. 

 *0.0694 gms. 



Gain in dry 



weight per 

 ghni2. 



Exp. No. 2. 

 0. 1102 gms. 

 . 3236 gms. 

 0.2468 gms. 

 0.2361 gms. 

 0.3433 gms. 



0. 1.502 gms. 

 . 36.50 gms. 

 0.2585 gms. 

 . 4524 gms. 

 0.2457 gms. 



♦The plants had been in.jiircii and consequently these figures arc not reliable. 



These experiments were i-irried out in the green lionse during 

 the month of February. Plants in the o])en in the summer time 

 average twice as much photosynthate. 



The following conclusion can be deduced from the above table: 

 1. The dry ^^■oigllt per unit area of leaves of seedlings grown 



