Abstract
Wollemi pine (Wollemia nobilis) does not shed individual leaves but instead cleanly self-prunes the whole first-order branch with all the leaves still attached. A zone of stranded xylem at the branch base, the site of branch abscission, is described here in relation to the profusion of bordered pits and ray parenchyma cells that occur in this region. We propose that the much higher occurrence frequencies of these two features, compared to those in the stem and in the outer regions of the branch, results in a zone of radially-orientated weakness which facilitates branch abscission. We also suggest that since the stranded xylem region has a smaller cross-sectional area than the outer regions of the branch, the prevalence of bordered pits promotes water flow, and thus may alleviate the effects of this region on water supply to the foliage. Our observations represent, to the best of our knowledge, the first report of the involvement of bordered pits and ray parenchyma in branch abscission.
Original language | English |
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Pages (from-to) | 225-236 |
Number of pages | 12 |
Journal | IAWA Journal |
Volume | 29 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2008 |