Mumeek 



-87 — 



Nutrition and Metabolism 



day, therefore those 6 days old had received 4 photoperiods, those 12 days 

 old 10, etc. All carbohydrates are expressed as glucose. Under "total 

 carbohydrates" is understood the sum of total sugars, starch and so-called 

 hemicelluloses. 



Table 3 : Effects of photoperiod on carbohydrate metabolism of soybean plants, var. 

 Biloxi — in percentages of dry tveight: — 



Description of Total 



Plant Material Total Sugars Starch Carbohydrates 



Plants 2 days old 



Stems 3.16 3.57 25.95 



Cotyledons 7.28 .32 24.10 



Long day Short day Long day Short day Long day Short day 



Plants 6 days old 



(.2 + 4 days) 



Stems 2.52 2.35 2.13 1.08 21.25 12.52 



Leaves 2.03 1.70 .84 .84 10.93 9.72 



Cotyledons 1.70 2.52 .58 .00 13.32 11.09 



Plants 12 days old 



(2 + 10 days) 



Stems 1.87 1.35 1.18 1.56 13.85 10.19 



Leaves 1.88 1.22' 1.69 1.65 12.05 18.29 



Cotyledons 2.17 2.22 .92 1.00 18.82 17.54 



Plants 20 days old 



(2 + IS days) 



Stems 1.71 1.65 1.16 1.26 12.43 17.13 



Leaves 1.87 1.09 2.13 1.00 17.23 12.17 



Plants 27 days old » 



(2 + 25 days) 



Stems 1.16 1.32 .35 1.24 14.98 18.80 



Leaves 1.96 2.52 1.16 .85 15.76 14.65 



Plants 33 days old 



(2 + 31 days) 



Stems 3.49 1.74 3.25 9.80 23.45 26.06 



Leaves 6.45 4.47 4.5S 3.82 25.62 19.09 



Plants 40 days old 



(2 -f 3S days) 



Stems 3.49 4.24 6.04 19.58 29.75 42.55 



Leaves 5.77 4.33 10.56 12.54 32.06 32.60 



As one would anticipate, the curtailed growth in height of the plants 

 seems to have affected also changes in enzyme activity (Hibbard, 9), 

 which probably preceded the accumulation of organic materials. 



While the initiation of the sexual state is most likely the function of a 

 special catalytic substance (hormone), the rapid increase in food sub- 

 stances may be considered a kind of assurance of nutrition for the de- 

 veloping flowers, but especially the fruit and seeds. The proper develop- 

 ment of the reproductive organs and associated tissues and the successful 

 setting of seeds and their growth depends very much upon the food re- 

 serves of the plant, chiefly on the various nitrogen and carbohydrate com- 

 pounds. Lacking an ample food supply, flowers will not develop and set 

 fruit normally, certainly not in large numbers. 



From the evidence at hand it is not clear whether in the soybean 

 (Biloxi) the reduced photoperiod (7-hour day) effects independently in- 

 duction of reproduction and inhibition of vegetative growth. There is the 

 possibility that a special catalytic substance may be produced by the young 

 floral organs, which inhibits stem elongation. Reduction in growth prob- 

 ably started considerably before the 12th day, which was somewhere near 



