Effect of the Sol-Gel Transformation in Clay-Water Systems on Biological Activity: II. Sodium Uptake by Corn Seedlings
1970
Baker, D. E. | Low, P. F.
Homoionic Na- and K- clay were prepared from the < 2µ fraction of Wyoming bentonite. The Na- clay separately, or combined with the K-clay, was mixed with water to produce clay-water systems having different clay contents. These systems were extruded through a hypodermic needle to orient the particles within them. Thereafter, some of them were disturbed by tapping their containers on the laboratory bench. Then the following quantities were measured on all or part of them: viscosity, relative partial molar free energy, (F̄ − F̄°), of NaCl, KCl and HCl, and water tension. It was found that the viscosity, the (F̄ − F̄°) of HCl, and the water tension were decreased by disturbing the clay systems, whereas, the (F̄ − F̄°) of both NaCl and KCl were increased. The physical significance of these changes was discussed. Samples of the Na- clay systems were mixed with 22ᴺᵃ and extruded around the radicles of corn seedlings (Zea mays L.). Then Na⁺ uptake was determined by analyzing the seedlings for ²²Na. It was found that Na⁺ uptake increased curvilinearly with Na- clay content in the range 0–4% clay and then leveled off. In the curvilinear range, Na⁺ uptake was directly proportional to the (F̄ − F̄°) of NaCl. Combined samples of Na- and K- clay were also mixed with 22Nₐ and extruded around the radicles of corn seedlings. The K- clay was used to maintain consistency and yet dilute the Na- clay enough so that the seedlings would respond to changes in the (F̄ − F̄°) of NaCl. As before, some of the systems were disturbed by tapping. It was found that Na⁺ uptake was greater from the disturbed than from the undisturbed systems. And since the disturbance also increased the (F̄ − F̄°) of NaCl, it was concluded that Na⁺ uptake depended on this quantity.
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