Absorption of copper by wheat, rye and some hybrid genotypes

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Abstract
The physiological basis of genotypic differences in efficiency of absorption of copper from soils deficient in that element was investigated using short term uptake studies with 64Cu. Seedlings were grown in complete nutrient solutions (about one‐tenth Hoagland solution) at 18°C under high‐pressure sodium vapour lamps until 12 days old when 64Cu was introduced to the culture medium. After a one‐hour absorption time, the plants were desorbed in cold 0.05 mM CaSO4 before counting. The rate of absorption of copper from solutions of 0.01 μM Cu was slightly higher for ryes than for wheats, with triticales intermediate. This proved to be the general pattern regardless of whether uptake was expressed on the basis of root fresh weight, surface area or volume. However, important changes in the ranking did occur and it proved to be difficult to find a reasonable basis on which to compare genotypes. The higher efficiency of rye in extracting copper from copper‐deficient soils may lie in its root system geometry. At 12 and 21 days, despite a lower weight of roots, rye had a greater root length than wheat, brought about primarily by smaller diameter of both main axes and lateral roots and a higher branching rate of first order lateral roots. In these characters triticale was generally in an intermediate position. Rye also translocated more copper from roots to shoot under the same conditions. The greater copper efficiency of rye compared to wheat appears to depend on a number of properties of its root system, and perhaps of the shoot as well; triticale appears to be intermediate in expression of these characters from its rye parent.