DISTRIBUTION OF THE VELOCITIES OF ABSORPTION OF WATER IN THE ONION ROOT

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Abstract
A technique is described by which precise quantitative data on the velocities of absorption of tap water by different regions of the same intact root may be simultaneously detd. under carefully controlled conditions. All regions of the onion root between the root cap (on which no measurements were made) and the bulb absorb tap water but at unequal rates. In young roots (less than 50 mm.) there is a unidirectional gradient of the distribution of velocities of water absorption, the region of max. absorption appearing at the apex. In older roots (more than 70 mm.) there exist 2 pronounced unidirectional gradients with maximum absorption velocities appearing in regions 40-60 mm. from the apex. The velocities of absorption of water are less in all root regions between the root cap and base in any one root when all the sister roots are present. Removal of sister roots increases the rates of absorption in all root regions of the remaining root. Each root region goes through a maximum with respect to age. exhibiting highest velocity rates when the root is 40-60 mm. long. With increase in age there is a shift of the region exhibiting maximum rates toward the apex.

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