Effects of Ca2+ and Cd2+ on the carbohydrate metabolism in sugar beet (Beta vulgaris)
1992
Greger, M. | Bertell, G.
Sugar beet (Beta vulgaris L. cv. Monohill) were cultivated in a nutrient solution with different combinations of Ca2(+) (36, 180, 720 or 3560 micromolar) and Cd2(+) (0, 1, 5 or 20 micromolar). The dry and fresh weights, the content of Ca2(+) and Cd2(+), sucrose, fructose, glucose and starch in 5-week-old plants was analysed as well as the rate of [14C]-sucrose uptake in discs from 3-month-old storage roots. The carbohydrate metabolism was indirectly affected by the presence of calcium or cadmium. Cadmium caused a diminished dry weight and carbohydrate concentration. The dry weight was unaffected by the Ca2(+) level but the carbohydrate distribution between storage and growth processes was affected; at low Ca2(+) in the tissue, the growth was retarded and the level of storage carbohydrate increased, while at high Ca2(+) the opposite was found. The [14C]-sucrose uptake decreased in tap roots cultivated at low Ca2(+). Long term exposure to Cd2(+) also decreased the sucrose uptake in tap roots. Direct Cd2(+) addition to the assay medium, however, increased the sucrose uptake, probably at the tonoplast, while Ca2(+) had no transient effect on the uptake. Cadmium increased the Ca2(+) concentration in the plant, but Ca2(+) did not affect the net-uptake of Cd2(+).
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