24 MASS. EXPERIMENT STATION BULLETIN 402 



The dissolved oxygen content of the water on a winter-flooded bog, when not 

 covered bj- ice, remains at or near a maximum determined by the temperature 

 of the water in accordance with well-known physical principles. 



When ice forms on a winter-flooded bog, the dissolved oxygen content of the 

 water depends on the relation between the amount of oxygen consumed in res- 

 piration by the cranberry vines, and by the microorganisms associated with 

 organic matter in and on the soil, and the amount given off in photosynthesis by 

 the cranberry vines and other green plants on the bog. Little or no oxygen is 

 given off in photosynthesis when, because of cloudiness, increased thickness of 

 the ice especially when snow is included in it, or snow on the ice, little or no light 

 is received by the vines and at such times the oxygen content of the water de- 

 creases. If conditions unfavorable for photosynthesis continue, all the oxygen 

 may disappear. 



Flower buds and the undeveloped new leaves within the terminal buds are the 

 first to be injured if oxygen is lacking, or are first to be killed if the lack of oxygen 

 continues long enough. 



Injury to the old leaves, during short periods of oxygen deficiency, probably 

 is prevented by the accumulation, in their intercellular spaces, of oxygen given 

 off in photosynthesis. 



Cranberry vines frozen into the ice on winter-flooded bogs are not injured by a 

 lack of oxygen during the winter-flooding period because they are at such a low 

 temperature that they are practically dormant and the amount of oxygen re- 

 quired is negligible. The little oxygen needed is probably obtained from the ice. 



The ability of cranberry vines to withstand oxygen deficiency appears to de- 

 pend to a certain extent on the amount of stored carbohydrates. Growers state 

 that cranberry vines are injured more severely after bearing a large crop than 

 after a small one or none. 



The dissolved oxygen content of the water on winter-flooded bogs under ice 

 in Mr ssachusetts varied from day to day according to the intensity and duration 

 of the light received by the vines. 



When there was snow on the ice, the intensity of the light received by the vines 

 was reduced according to the thickness of the snow cover; only about 5 per cent 

 of the incident light penetrated four inches of snow. When little or no light was 

 received by the vines, the dissolved oxygen content of the water decreased very 

 rapidly; all the dissolved oxygen was consumed within three or four days. 



An insufficient supply of oxygen in the water during the winter- flooding period 

 reduced the size of the crop the following season, but the reduction was not 

 always proportional to the degree or the duration of oxygen deficiency. Present 

 evidence indicates that the yield is reduced if the dissolved oxygen content of the 

 water ff Us below 3 cc. per liter (4 p. p.m.) even for a few days. Oxygen depriva- 

 tion over a longer period caused a further reduction in yield. The smaller yield is 

 the result of the death of flower buds, loss of old leaves, injury to the flower buds 

 which causes them to fail to set fruit, and reduction in the size of fruits. 



Some modifications of winter-flooding practices are suggested as remedial or 

 preventive measures. The flooding period should be made as short as possible 

 and the water as shallow as possible. Vines may be frozen into the ice over win- 

 ter; or a bog may be flooded as usual and, after several inches of ice have formed 

 over the bog, the water may be drawn out from under the ice allowing it to drop 

 down onto the vines and remain there until it melts. Both of the last two methods 

 have been used successfully in Wisconsin, and the latter method probably could 

 be used successfuUv in Massachusetts. 



