12 MASS. EXPERIMENT STATION BULLETIN 402 



these require the most oxygen and are the first to be injured or killed as the 

 oxygen supply is depleted. 



Nothing is known as to the relative physiological activity of the leaves as com- 

 pared with that of the flower buds and other parts of the termmal buds during 

 the winter. On bogs in Massachusetts the leaves are injured or killed onh- after a 

 prolonged period of deficiency or absence of oxygen and only after the flower 

 buds and some or all of the undeveloped new leaves within the terminal buds 

 have been injured or killed. This may be not so much because physiological 

 activity is less in leaves than in the flower buds and other parts of the terminal 

 buds as it is that the leaves, under most conditions, have a greater available oxygen 

 supply than other parts. This is because photosynthesis goes on only In the 

 leaves. The oxygen given off in the process diffuses through the walls of the cells 

 within the leaves into the intercellular spaces and from there through the stomata 

 into the water in which the vines are submerged. However, because oxygen 

 diffuses through w-ater very slowly, and since that is the only means by which it 

 can pass from the leaves into the surrounding water, only a small part of it escapes 

 and, therefore, it accumulates in the intercellular spaces of the leaves. This 

 accumulated oxygen is used by the leaves for respiration, and enables them to go 

 without injury through short periods when there is little or no dissolved oxygen 

 in the water. However, the leaves are injured or killed during prolonged periods 

 of very low oxygen content resulting from the exclusion of light by snow on the 

 ice since, at such times, there is either no accumulation of oxygen in the inter- 

 cellular spaces or not enough to supply the amount needed for respiration. 



Parts of cranberry vines in which there is no photosynthesis are supplied en- 

 tirely by the diffusion of oxygen from that in solution in the water around them. 

 Although diffusion is very slow, enough oxygen is transferred in this way to 

 supply the demand of respiration of the various parts of the vines as long as the 

 amount of dissolved oxygen in the water is not less than a certain minimum, 

 which is now placed at 3 cc. per liter (4 p. p.m.) or about 1.5 per cent of the amount 

 normally present in the air. When there is less than that amount, it cannot 

 be supplied rapidly enough to meet the demand of respiration thus causing injury 

 of varying severity. It is for this reason that the flower buds and undeveloped 

 new leaves within the terminal buds, with their relatively high oxj^gen require- 

 ment, are the first to be injured or killed. 



The temperature of cranberry vines in water under ice is the same as that of 

 the water;. but when the vines are frozen into the ice their temperature becomes 

 the same as that of the ice, which is often much lower than 32°, as the tempera- 

 ture of the ice soon comes to that of the air. Vines on shallowly flooded bogs or 

 parts of bogs, in Massachusetts, are often frozen into the ice. Some growers in 

 Wisconsin freeze the vines into the ice as a means of preventing leaf-drop.^ 

 Vines frozen into the ice usually are at a temperature low enough to very nearly 

 stop their physiological activity; i. e., the vines are practically dormant and hence 

 require only a negligible amount of oxygen. This probably is obtained by diffu- 

 sion from the ice, since the ice contains oxygen in solution, and thus the vines are 

 carried through the winter without injury. 



The Ability of Cranberry Vines to Withstand Oxygen Deficiency 



Cranberry vines in different locations, or in different years, are not injured to 

 the same degree by a known low dissolved oxj-gen content of the water for a 

 known time. Vines in one location are sometimes Injured more by a lack of 



^Rogers, L. M. Bog Construction and Management in Wisconsin. Wis. State Cranberry Grow- 

 ers' Assoc. 46th Ann. Rpt. 37-38. 1933. 



