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This article in AJ

  1. Vol. 64 No. 4, p. 459-462
    Received: Jan 9, 1971



Influence of Soil Temperature on the Geotropic Response of Corn Roots (Zea mays L.)1

  1. P. N. Mosher and
  2. M. H. Miller2



Experiments were conducted in controlled temperature cabinets to determine the factor that caused corn (Zea may L.) radicles to grow nearly straight down from the seed in a greenhouse experiment conducted during the summer, and horizontally in a second experiment conducted during the winter.

The possibility of horizontal growth caused by atrazine residues in the soil of the second experiment was eliminated when this type of growth was observed in vermiculite as well. Nearly vertical growth was observed when radiant energy from a heat lamp was directed onto the soil surface. The possibility that the roots followed a temperature gradient was eliminated by demonstrating vertical growth toward as well as away from the radiant energy. The soil temperature at the seed was found to be the primary factor involved. The angle of radicle growth varied from 30° from the horizontal at 18 C to 61° from the horizontal at 36 C.

The influence of soil temperature on the direction of radicle growth explains many observations on root growth from the literature. It appears that the direction of growth of the radicle as well as that of the seminal and nodal roots is controlled by soil temperature.

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