The longitudinal contraction, a natural phenomenon of many plants, which results in lowering the basal portion of the plant deeper in the soil, is apparently accomplished in various ways. In both alfalfa and sweet clover the crowns are pulled vertically downward two to four inches during the first season. This is accomplished chiefly by the contraction vertically and the expansion radially and tangentially of parenchymatous cells that are continuously being formed in isolated groups scattered among the vascular elements. The development and expansion of these intercalated masses of parenchyma separate the vascular elements into tortuous strands, the tortuosity of which results in the shortening of the entire vascular cylinder. The strands of libriform fibers in the cortex are shortened in the same manner.
Proceedings of the Iowa Academy of Science
©1933 Iowa Academy of Science, Inc.
Simonds, Austin O. and Martin, J. N.
"Contraction of the Roots and Crowns Medicago and Melilotus,"
Proceedings of the Iowa Academy of Science, 40(1), 83-84.
Available at: https://scholarworks.uni.edu/pias/vol40/iss1/27