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Agronomy Journal Abstract -

Chlorotic Dieback in Flax1


This article in AJ

  1. Vol. 70 No. 3, p. 501-505
    Received: Oct 24, 1960

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  1. J. T. Moraghan2



“Chlorotic dieback” of flax (Linum usitatissimum L.) is characterized by leaf chlorosis, dieback of terminal buds, and development of lateral branches; its occurrence is most frequent under cool soil conditions. The cause of this disease was studied under greenhouse conditions. Flax was grown on a calcareous soil (Calciaquoll) at three soil temperatures (7, 16, and 24 C) in the presence and absence of different levels of FeEDDHA and ZnSO4. The dieback syndrome occurred in the absence of Zn at 16 and especially 7 C but not at 24 C. Zinc accumulation in plant tops for a given fertilizer treatment dcreased progressively as soil temperature was reduced from 24 to 7 C. Zinc deficiency in mature plants was associated with plant Zn levels less than approximately 20 ppm, and its severity was inversely related to soil temperature. FeEDDHA decreased Zn and Mn accumulation in plant tops and, in the absence of added Zn, increased degree of Zn deficiency. FeEDDHA with added Zn eliminated leaf chlorosis and spotting of older leaves and increased Fe concentration in young plants. Dieback of main stems and subsequent branch development from the cotyledonary node, the chief features of “chlorotic dieback”, were found to result from Zn deficiency; however, the leaf chlorosis aspect of the disease was influenced by available soil Fe. Apical dominance in flax was decreased by Zn deficiency; soil temperature indirectly affected this characteristic through its influence on plant Zn accumulation. However, the influence of soil temperature on apical dominance was more complex since lateral branch development even in the presence of added Zn was greatly affected by soil temperature. Phosphorus accumulation in flax was markedly decreased by low soil temperatures.

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