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Plastochron Indices for Juvenile and Mature Forms of Hedera helix L. (Araliaceae)

Robert E. Cordero, John R. Murray and Wesley P. Hackett
American Journal of Botany
Vol. 72, No. 2 (Feb., 1985), pp. 324-327
Stable URL: http://www.jstor.org/stable/2443560
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Plastochron Indices for Juvenile and Mature Forms of Hedera helix L. (Araliaceae)
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Abstract

English ivy (Hedera helix) plants were assessed for the applicability of the plastochron index (PI). Juvenile ivy satisfied all requirements for the use of the PI and showed a plastochron of 4.23 days. Mature ivy grown under long day conditions flowered after 11-12 leaves. Two distinct groups of leaves were produced with different plastochrons (0.83 and 3.2 days, respectively) and leaf morphologies. Long-day-grown ivy did not satisfy the requirements for the use of the PI. Short-day-grown mature ivy continued production of leaves beyond the 12th leaf. Vegetative growth was perpetuated for at least 25 plastochrons. By 19 plastochrons (ca. 41 days after budbreak) a linear PI vs. time relationship was established with a plastochron of 3.16 days. This newly acquired ability to maintain vegetative growth in mature ivy plants may allow a direct comparison with the vegetative indeterminant juvenile in order to assess possible anatomical factors responsible for phase stability and phase change using the PI as a basis for comparison.

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