Exudation of ninhydrin-positive compounds by pea-seedling roots: A study of the sites of exudation and of the composition of the exudate
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The sites of exudation of young pea roots were localized. The tips of the main root as well as those of the lateral roots were found to be important sites of exudation. Furthermore, a release of ninhydrin-positive compounds occurred during the formation of lateral roots, a process whereby the main root is severely damaged.
Of the free amino compounds exuded by pea-root tips, a compound not yet fully identified (unknown Y) was quantitatively by far the most important, while homoserine was only present in minor quantities. In extracts of 2-mm slices of tips of young pea-seedling roots, ‘unknown Y’ was predominant in extracts of the first 2-mm slices, whereas homoserine was quantitatively most important in extracts of the second 2-mm slices.
Roots of pea seedlings cultivated in nutrient solution during a period in which lateral roots had developed, released predominantly homoserine while ‘unknown Y’ came second. Lateral root formation obviously caused release of homoserine which was most likely liberated from the main root by wounds originating from the formation of lateral roots.
KeywordsPlant Physiology Nutrient Solution Lateral Root Free Amino Minor Quantity
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