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Lect03s08papersaving - 1 Last time Every shoot and root tip...

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Lect 03 2006 1 Last time: Every shoot and root tip has an apical meristems. The regions are the source of new cells in the body that contribute to growth in length of branches and roots. Cells in the meristem that have just finished dividing are small and undifferentiated; there is a gradient of differentiation such that cells mature and differentiate at some distance from the tip. We looked a “generic” plant cell and talked about the structures in plant cells that are only found in plant cells: vacuoles, cell walls and plastids. Today: Plant tissue systems and cell types in those tissues. General arrangement of plant tissue systems: Roots: XS, LS Shoots: XS, LS Begin at the outer surface: I. Plant tissues A. Epidermis (the dermal tissue system) The outermost layer of cells in contact with the external environment. 1. Function: a. Prevents water loss and dehydration of plant cells. b. Gas exchange (CO2 in; O2 and H2O out) c. Protection and defense: fungi, herbivorous insects d. First layer of protection against harmful uv radiation 2. Structure: a. a typical epidermal cell 1. range in shape from elongate in long linear leaves to puzzle shaped in broad leaves 2. single layer of cells 3. living at functional maturity 4. all typical organelles except chloroplasts 5. primary cell walls with modifications on the outer wall: i. the cuticle --the outermost boundary --a unique layer that restricts water loss from inside the plant --secreted by the epidermal cells in the outer wall --consists of a mixture of cutin ( complex fatty acid) and waxes. The outer most layer may be very waxy.
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