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chapter six leaves (leaf blade ( also called lamina) (petiole ( stalk)…
chapter six leaves
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vascular tissues
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minor veins
the most important for releasing water from xylem and loading sugar into phloem, whereas the midrib and lateral veins are involved mostly in conduction
bundle sheath
bundle sheath extension
veins, especially larger ones, often have a mass of fibers above, below, or both
such fibers help give rigidity to the blade and are believed to provide an additional means by which water moves form the bundle out to the mesophyll
they both conduct and support the leaf blade,they may have many fibers arranged as a sheath
monocots
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the cell becomes involved until the primordium is a cylinder that completely or almost completely encircles the shoot apical meristem
apical meristem cells adjacent to the primordium grow upward along with it, becoming party of the primordium and giving it a hood-like shape
Succulent leaves
numerous adaptation permit plants to survive in desert habitats, one of the most common being production of succulent leaves
this is characteristic of species in the families crassulaceae(contains Kalanchoe and Sedum), portulacaceae, and Auziaceae(ice plant), among other.
Succulent leaves are thick and fleshy, a shape that reduces the surface-to-volume ratio and favors water conservation. some leaves are cylindrical or even spherical, the optimal surface-to-volume shape,
epidermis
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mesophyll
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spongy mesophyll
open, loose aerenchyma that permits carbon dioxide to diffuse rapidly away from stomata into all parts of the leaf's interior
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leaves of conifers
in almost all species of conifers, leaves are sclerophylls: they have a thick cuticle, and their epidermis and hypodermis cells have thick walls.
most conifer leaves contain unpalatable chemicals. conifer leaves are always simple, never compound, and have only a few forms.
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Bud Scales
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spines
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the green cactus body has microscopic green leaves, and the clusters of spines are their axillary buds
Tendrils
tendrils of many plants(peas, cucumbers, and squash) are another form of modified leaf.
unlike photosynthetic leaves, tendrils grow indefinitely and contain cells that are capable of sensing contact with an object.
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