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Absorption, Distribution, and Form of Ca in Relation to Ca Deficiency (Tip Burn) of Sugarbeets¹

Sugarbeet plants (Beta vulgaris L.) were grown in the greenhouse in nutrient solutions containing 0.33 and 5.0 meq Ca/liter. Carrier-free ⁴⁵Ca was added at transplanting to nutrient solutions of a set of sugarbeet pots and the rest were left untreated. Two weeks later, the ⁴⁵Catreated pots were harvested and another set was treated with ⁴⁵Ca. This process was repeated for three more harvests with addition of ⁴⁵Ca at 2, 4, and 6 weeks and harvesting, respectively, at 4, 6, and 8 weeks after transplanting. All in all, there were four ⁴⁵Ca additions and four harvests. At each harvest, the various parts of the plant were assayed for ⁴⁵Ca that was associated with Ca soluble hi 80% alcohol, as chloride and nitrate, in water as salts of organic acids, in 1 N NaCI as pectate, in 2% CH₃COOH as di- and triphosphate, in 0.6 N HCI as oxalate and insoluble residue.

Symptoms of Ca deficiency were associated with an incomplete uptake of Ca from the nutrient solution, a high rate of Ca consumption by the storage roots, and a failure to translocate sufficient Ca to the tops to support rapid young leaf growth, but were not associated with the formation of an insoluble Ca compound(s). Since ⁴⁵Ca was detected in various forms in all parts of Cadeficient sugarbeets, the pathway for Ca remained functional even as the symptoms increased in severity.

Calcium phosphate, rather than Ca oxalate, was at a high concentration hi all parts of the Ca-deficient and Ca-sufficient plant, except Ca oxalate exceeded Ca phosphate in the mature and old blades of the Ca-sufficient plant. If Ca immobility inhibits the transport of Ca from older to younger parts, then the formation of Ca phosphate could be a limiting factor under deficiency and not under sufficiency conditions.

Key Words: Beta vulgaris L. • Radioactive Ca • Nutrient solution • Storage roots

² Staff research associate and plant physiologist, Dep. of Soils and Plant Nutrition, Univ. of Calif., Berkeley, CA 94720, respectively.

Received for publication November 20, 1974.