WEATHER IN CRANBERRY CULTURE 13 



oxygen for a few days than are those in another location where the oxygen con- 

 tent was equally low for the same length of time. Or, sometimes, vines that were 

 for a known time in water of known low oxygen content are injured less than 

 those that were for an equal time in water of higher oxygen content, or than those 

 in water of equalh- low oxygen content for a shorter time. 



The difference in the ability of cranberry vines to withstand oxygen deficiency 

 appears to depend, at least to a considerable degree, on the amount of stored 

 carbohydrates (sugars, starch) in the vines in the autumn preceding the winter- 

 flooding period. Vines in which there is a large amount of stored carbohydrates 

 are injured less than those in which, for any reason, the amount is small. The 

 reason for this seems to be that cranberry vines are able to break down the carbo- 

 hydrates stored in their leaves and stems to obtain the oxygen needed for respira- 

 tion, at least for a limited time when the dissolved oxygen content of the water is 

 too low to supply it, thus preventing injury from oxygen deficiency. However, 

 in some plants, some of the end products formed when respiration is carried on 

 in this way are toxic and if present in more than very minute amounts usuallj- 

 cause the death of the parts in which they accumulate. If this also is true of 

 cranberry vines they probably would be able to withstand oxygen deficiency for 

 onl}' a comparatively short time even when there is an ample supply of stored 

 carbohydrates. 



The amount of stored carbohydrates in cranberry vines preceding a winter- 

 flooding period depends, aside from weather conditions, on the size of the crop 

 immediately preceding the flooding period and on the freedom of the vines from 

 previous injury. Growers report that cranberry vines are injured more severely 

 after a large crop than after a small one or none. This is because the carbohydrate 

 reserves in the vines are either used up or greatly reduced in the production of a 

 large crop. The amount of stored carbohydrates in the vines when a bog is 

 flooded for the winter then depends on the amount stored between the time the 

 berries are picked and the Lime the bog is flooded for the winter. This amount 

 may or may not be sufficient to protect the vines against a lack of oxygen during 

 the winter flooding period, since the amount stored depends upon autumn weather 

 conditions, which vary greatly from year to year. 



THE COURSE OF THE DISSOLVED OXYGEN CONTENT OF 

 THE WATER ON A WINTER-FLOODED BOG 



Although it has been found that the dissolved oxygen in the water under ice on 

 a winter-flooded bog sometimes becomes greatly reduced or disappears, the exact 

 conditions under which this occurs, or the extent to which the oxygen content 

 varies and the relation of various factors to variations jn oxygen content, were 

 not known. Neither was it known how much the dissolved oxygen content must 

 be reduced and how long the vines must remain in water of a given reduced oxygen 

 content to cause injury of different degrees of severity. To obtain information on 

 these points, determinations of the dissolved oxygen in the water at three sta- 

 tions on the State Bog were made weekly from January 15 to March 20, 1941. 

 The bog had frozen over about December 8, 1940, and from that time was com- 

 pletely covered with ice until about March 13, 1941. Determinations of the 

 dissolved oxygen content were made by the Winkler'^ method. The amount of 

 dissolved oxygen In the water on days when samples were taken is shown in Fig- 

 ure 4. 



^Winkler, L. W. Ber. deut. chem. Ges. 21: 2843-2854. 1888. See also U. S. Pub. Health Serv. 

 Bui. 151. 1925. 



