42 MASS. EXPERIMENT STATION BULLETIN 388 



during the winter flooding period was known. The yield of berries of each variety 

 inside the tanks and on measured areas outside was determined. 



The effect of an insufficient supply or of complete deprivation of oxygen over 

 a period of a month or more during the winter flooding period is shown clearly 

 by the reduction in yield of berries from vines inside the tanks in comparison with 

 vines outside. Furthermore, the yield outside but near the tanks was very much 

 less than that from vines on slightly higher ground and therefore less deeply 

 flooded. The yields, in barrels per acre, were as follows: Early Black, inside 

 tank 28, outside near tank 34, on slightly higher ground 75; Howes, in the cor- 

 responding locations, 50, 72, and 110; and McFarlin, inside tank 39, outside on 

 higher ground 81. 



Although the dissolved-oxygen content of the water on the less deeply flooded 

 areas during the winter was not determined, it has been found repeatedly that 

 the oxygen content of water is less in deep places than in shallow, even a few 

 inches making a significant difference,- particularly when there is ice over the bog. 

 It is probable, therefore, that the oxygen content of the water in the less deeply 

 flooded "high" places did not fall below 2 cc. per liter for more than one or two 

 days during the winter, if at all. This indicates that if the dissolved-oxygen 

 content of the water is less than 2 cc. per liter for even a few days the j'ield is 

 greatly reduced. A longer period of oxygen deprivation caused a further reduc- 

 tion in yield, but even within a variety the reduction was not proportional to the 

 length of time during nvhich the oxygen deficiency existed. Prolonged oxygen 

 deficienci' affected vines of different varieties differently. There was no oxygen 

 in the water inside the tank on Howes vines for nearly two months; yet these 

 vines yielded better than Early Black vines inside a tank in which the ox^'gen 

 in the water was less than 1 cc. per liter for not more than a month and approached 

 exhaustion for about two weeks only. This probably is because the Early Black 

 vines had been badly injured by a lack of oxygen in the water during the flooding 

 period of the Winter of 1939-40 and therefore were more susceptible to injury. 



The first effect of an oxygen deficiency during the winter flooding period is to 

 reduce the number of flowers that set fruit. Injury of this kind apparently may 

 occur if there is less than 2 cc. of dissolved oxygen per liter in the water for as 

 short a time as 3 or 4 days. In all three varieties the percentage cf flowers setting 

 fruit was lowest on vines inside the tanks, where the oxygen deficiency was great- 

 est, and was lower on vines in slightly deeper water than on those most shallowly 

 flooded, although in some cases the difference was small. 



A greater deficiency of oxygen or a deficiency over a longer time causes the 

 death of flower buds and then of the uprights on which the flowers are borne. 

 The percentage of dead buds on vines of all three varieties in the areas outside 

 but near the tanks was considerably greater than it was on vines on slightly 

 higher ground. In the Early Black and Howes varieties the percentage of dead 

 buds on vines inside the tanks was slightly less than on those outside, whereas 

 it should have been greater. One reason for this discrepancy may be that more 

 of the flower buds on vines inside the tanks than on those outside were killed at 

 such an early stage of development that they were not detected when the counts 

 were made. This is indicated by the lower average number of flowers per upright 

 for these varieties on vines inside than on those outside the tanks. Another 

 reason is that in making the counts only flowering uprights were taken; no atten- 

 tion was paid to sterile ones, a considerable proportion of which probably were 

 flowering uprights on which the buds had been killed at a very early stage of 

 development. For the same reasons the values for the percentage of flowers 

 setting fruit on vines of the Early Black and Howes varieties inside the tanks 

 are higher than they would otherwise have been. 



The average size of berries from vines inside the tanks was smaller than that of 



