236 Mineral Nutrition of Plants 



and shoot relative to oxygen supply. The effect of partial pressure of 

 oxygen in the bathing medium of abscised roots on inorganic solute 

 accumulation has been pointed out earlier. Studies with intact plants 

 suggest that some species, for example rice, might develop and carry 

 on internal processes at lower oxygen levels in the bathing medium 

 than others. The similar aerobic requirements for accumulation of 

 inorganic solute by abscised roots of rice, barley, and tomato were 



TABLE IX 



Fresh Weight and Potassium Concentration of Expressed Sap of Plants 

 Grown 6 Weeks in Drained and Submerged Clay.— Vlamis and Davis (88) 



*Clay soil 

 Note: Submerged plant roots were gradually exposed to increasing soil moisture until the 

 water level was one inch above the soil surface. Plants of both sets were frozen and sap ex- 

 pressed and analyzed for potassium concentration. 



clearly shown in Figures 8A and 8B. Earlier observations indicating 

 decreased growth of some species under adversely low oxygen condi- 

 tions in soils were confirmed by Vlamis (88). Plant development under 

 good and poor drainage is indicated by the fresh weights of plants in 

 Table IX. Potassium analyses on roots of these plants indicate no 

 adverse effect of treatment on accumulation with rice, but a reduction 

 in the same process with barley and tomato, particularly the latter. 

 Controlled experiments with solution cultures supplied with various 



