primarystem213-page6 - bundles have an anastomosing or an...

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The Shoot System: Primary Stem Structure - 6 Monocot Stem Variations Most monocots are reasonably small, herbaceous plants. There are some notable exceptions, however, such as the palms, which attain great height and dimension. Most monocots have no secondary growth, even perennial monocots. The common monocot families are the lily, grass and orchid families. Some distinctive monocot stem features: Monocot vascular bundles are closed. No procambium remains so generally monocots have no cambium (and no increase in girth) There may be 2 or 3 layers of sclerenchyma beneath the epidermis layer for strength and support of the stem structure. Some parenchyma cells may also develop thickened walls in monocot stems as they mature. Vascular bundles are "scattered" in appearance throughout the ground parenchyma, so there is no distinction between cortex and pith. Vascular
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Unformatted text preview: bundles have an anastomosing, or an interwoven pattern in longitudinal section. The parenchyma cells between vascular bundles are just referred to as ground tissue. This is the third vascular bundle pattern common in primary growth of stems. • Most monocot vascular bundles contain two large xylem vessels toward the interior of the bundle, and some smaller vessels between them. The very first vessels formed usually collapse from stretching during growth, leaving an air space. As a result the vascular bundle often takes on the appearance of a "clown face". Phloem is always located toward the epidermis layer, and contains no fibers. A sclerenchyma bundle sheath surrounds each vascular bundle. Monocot stem, xs Monocot vascular bundle...
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