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SEASONAL VARIATION IN THE SECONDARY PHLOEM FROM THE MAIN TRUNKS OF WILLOW AND SYCAMORE TREES
Author(s) -
LAWTON JUNE R.
Publication year - 1976
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1976.tb04672.x
Subject(s) - phloem , sieve tube element , cambium , callose , botany , vascular cambium , sieve (category theory) , biology , xylem , cell wall , mathematics , combinatorics
S ummary The structure of the phloem near to the cambium is described for mature trees of Salix fragilis L. and Acer pseudoplatanus L. Changes in the structure of the phloem were investigated by light and electron microscopy. Measurements of the dimensions of the sieve tube elements show that those formed during the winter months are small in diameter and that the area of phloem formed from June to September is greater and the diameter of the individual sieve tubes larger. In both species there are some sieve tubes close to the cambium with open pores in the sieve plates throughout the year. The extent of callose deposition of the sieve plates, as shown by u.v. fluorescence microscopy, can be correlated with the age of the sieve tubes. The sieve plates in Acer are simple and those in Salix , compound and very oblique. The depth of phloem showing callose fluorescence changes during the year. There is an increase in the depth of phloem with open pores on the sieve plates through to September in both Willow and Sycamore, which can be correlated with a natural increase in temperature and day length.