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A QUANTITATIVE STUDY OF SIEVE‐TUBE DIFFERENTIATION IN VEGETATIVE SHOOT APICES OF COLEUS
Author(s) -
Jacobs William P.,
Morrow Ielene B.
Publication year - 1967
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1967.tb10660.x
Subject(s) - biology , sieve tube element , shoot , coleus , xylem , botany , sieve (category theory) , elongation , horticulture , phloem , materials science , mathematics , combinatorics , ultimate tensile strength , metallurgy
Quantitative methods, with round‐the‐clock collecting of large samples in successive years, have uncovered several new phenomena of sieve‐tube differentiation in young leaves of Coleus vegetative shoots. In small leaves (1–350 μ ), there are no sieve tubes in the leaf itself, but they differentiate acropetally in the two traces to each leaf. Regression lines fitted to the data for leaf length vs. most distal position of sieve tubes in the traces support the view that differentiation is steady and acropetal, but they also reveal that differentiation in the traces falls steadily farther behind elongation of the leaf. Leaves more than 500 μ long have sieve tubes close to their tips. An intensive search of leaves of intermediate lengths revealed an isolated locus of sieve‐tube differentiation. These relationships were reproducible year after year. Every plant with discontinuous strands of sieve tubes in the second leaf pair had discontinuous xylem in the third. This isolated locus was not seen before, probably because of small samples and daytime collections; most of our cases were from night collections.