Examination of morphological changes in the first formed protoxylem in Arabidopsis seedlings |
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Authors: | K Kobayashi F Takahashi M Suzuki H Suzuki |
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Institution: | (1) Photodynamics Research Center, RIKEN (The Institute of Physical and Chemical Research), Sendai, Japan, JP;(2) Botanical Garden, Graduate School of Science, Tohoku University, Sendai, Japan, JP;(3) Department of Biotechnology, School of Science and Engineering, Ishinomaki Senshu University, Ishinomaki, Japan, JP |
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Abstract: | We examined morphological changes in the first-formed protoxylem vessels in Arabidopsis seedlings. Between 2.5 and 8 days after imbibition, mean hypocotyl and root length increased 1.52 and 23.3 times, respectively.
In the 2.5-day-old seedlings, two continuous protoxylem vessels were present in the hypocotyl-root axis. In the 8-day-old
upper hypocotyls, six protoxylem vessels were observed, and in the lower hypocotyls, four protoxylem vessels and one or two
metaxylem vessels were observed. In the 8-day-old roots, there were two protoxylem vessels and two or three metaxylem vessels.
Two protoxylem vessels in the hypocotyls connected to two metaxylem vessels in the roots of 8-day-old seedlings. At the 0.3-mm
part below the hypocotyl-root boundary, the mean intervals of neighboring annular secondary wall thickenings in protoxylem
vessels in 8-day-old roots were 12.9% larger than those in 2.5-day-old roots. In more apical parts of 8-day-old roots, the
mean intervals fluctuated between 1.71 and 2.29 μm. In 8-day-old seedlings, metaxylem vessels were formed between 0.4 mm above
the hypocotyl-root boundary and 17 mm below the boundary. The intervals in these regions were not extended so much as protoxylem
vessels were collapsed. The first-formed protoxylem vessels presumably retain their water-conductive function after metaxylem
formation.
Received: April 10, 2001 / Accepted: November 7, 2001 |
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Keywords: | Arabidopsis thaliana Interval of annular secondary wall thickening Protoxylem vessel Root elongation Seedling |
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