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Structurally, phloem unloading in the maize leaf cannot be symplastic
Author(s) -
Evert Ray F.,
Russin William A.
Publication year - 1993
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.1537-2197.1993.tb15370.x
Subject(s) - sieve tube element , plasmodesma , phloem , sieve (category theory) , biology , vascular bundle , botany , leaf blade , ultrastructure , mathematics , combinatorics
Developing longitudinal vascular bundles of the leaf blades of maize ( Zea mays L. cv. W273) were examined with the transmission electron microscope to determine the frequency of plasmodesmata between the sieve tubes and their neighboring cells. Of particular interest were the protophloem sieve tubes, the first sieve tubes to mature in importing (all large and some intermediate) bundles. The protophloem sieve tubes, most of which lack companion cells, intergrade structurally with the thin‐walled metaphloem sieve tubes. Both the protophloem sieve tubes and the thin‐walled metaphloem sieve tubes and their companion cells (the sieve tube‐companion cell complexes) are virtually isolated symplastically from the rest of the leaf, precluding a symplastic mechanism of phloem unloading in the leaf blade of maize.