PAPERS ON BOTANY 133 



A METHOD OF PROPHESYING THE LIFE DURA- 

 TION OF SEEDS 



J. F. GROVES, UNIVERSITY OF CHICAGO 



Since former explanations of the loss of vitality of seeds in 

 storage conditions have proven incorrect, we have been led 

 to surmise that a gradual coagulation of the proteins in the 

 embryo may offer such an explanation. It has been shown by 

 Chick and Martin 1 that proteins do not have a fixed tempera- 

 ture point for coagulation, but that coagulation may occur at 

 any temperature provided the time of exposure be sufficiently 

 great. Buglia 2 has applied the following time temperature 

 formula to protein coagulation : T=a-b log Z, in which T= 

 temperature cent., Z=minutes of exposure, and a and b con- 

 stants. Lapeschkin 3 applied this formula to the coagulation of 

 proteins in active plant cells and found a close agreement in 

 theoretical and found values where time duration was short. 



In this investigation constant temperatures were obtained 

 by the use of the thermostat shown in figure 10. An external 

 water bath contains a vessel of smaller dimensions which is 

 connected with a water-cooled reflux condenser. Mixtures of 

 ethyl and methyl alcohol and water used to provide desired 

 temperatures and the seeds, in closed test-tubes, are suspended 

 through closed perforations. 



After quantities of seeds were exposed to a given temper- 

 ature for various lengths of time, they were sterilized in an 

 aqueous solution of silver nitrate and placed in sterile petri 

 dishes for germination. Daily records were kept as in table 

 I. Increased time of heating shows a delay in germination 

 as well as a fall in germination percentage which is also true 

 of seeds stored for a long time at room temperature. 



Table II shows the life duration at various temperatures as 

 found by experiment and the calculated life duration according 

 to the formula. The constants a and b were found by the 

 method of least squares from the found values of T and Z, and 

 from these T was calculated for 'the various values of Z. The 

 found values agree quite closely with a curve plotted for the 

 theoretical values. 



The temperature coefficient of life duration of wheat is 

 found to be 7 or 8 for each 10 degrees change of temperature. 

 Goodspeed 4 working with barley found a coefficient of life 



1. American Jour, of Physiology, 40:404, 1910; 43:1, 1911. 



2. Zeitschr. fur Chemi. and Industrie die Kolloide, 5:291, 1909. 



3. Ber. Bot. Gessels, 703-704, 1913. 



4. Botanical Gazette, 51:220-224, 1911. 



