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This article in AJ

  1. Vol. 62 No. 6, p. 815-818
     
    Received: May 11, 1970
    Published: Nov, 1970


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doi:10.2134/agronj1970.00021962006200060042x

Variation in Taproot Elongation Rate as Influenced by Composition of the Soil Air1

  1. M. G. Huck2

Abstract

Abstract

Elongation rates of cotton and soybean taproots were measured while the O2 content of a gas stream passing through the soil surrounding the roots was varied. Elongation rates were comparable to controls at all O2 concentrations above 10%. Elongation ceased completely within 2 to 3 min after all O2 was purged from the system with 100% N2 gas, and returned to normal shortly after 21% O2 was returned to the system, provided the period of anaerobiosis had not exceeded 30 min. Longer periods of complete anaerobiosis resulted in killing of a certain percentage of root tips until approximately 100% of the primary taproots were killed at 3 hr without O2 for cotton and 5 hr for soybeans. Oxygen levels from 2 to 5% resulted in an initial reduction in rate of taproot extension, followed by a gradual return to elongation rates comparable with controls. Although 3 to 5 hr of complete anaerobiosis evidently killed the terminal meristematic region of the taproots, new lateral growth developed from the cortex within a day or two after cessation of growth of the terminal meristems. Distribution of roots through a volume of soil may thus be influenced by oxygen availability and its distribution through time and space.

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