Photosynthesis: plants need resources for this process.
Shoot and root: these two structures aid the plant in obtaining these resources.
Vascular system: this internal transport system moves the resources within the plant.
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Basic Plant Anatomy
Figure 35.2, Purves's Life: The Science of Biology, 7th Edition
Cell Wall Formation
Cytokinesis in plants
Each daughter cell secretes glue that constitutes the middle lamella, forming a barrier between them.
Each daughter cell secretes cellulose and other polysaccharides to form a primary cell wall which continues to grow as the cell grows to its final size.
Secondary cell wall
Once cell expansion stops, a plant cell may deposit more polysaccharides to form a secondary cell wall.
This may be impregnated with lignin (characteristic of wood).
Figure 35.6, Purves's Life: The Science of Biology, 7th Edition
Plasmodesmata
Plasmodesmata are pores in the walls of adjacent cells that allow water and dissolved materials to move easily from cell to cell.
In this way, the plasma membrane from one cell can become continuous with the plasma membrane of the adjacent cell.
They are found only in primary cell wall.
Figure 35.7, Purves's Life: The Science of Biology, 7th Edition
Pits
Pits are large openings in the secondary cell walls that allow the plasmodesmata in the primary cell walls to be exposed.
This allows water and dissolved materials to pass from cell to cell through the plasmodesmata.
Take-home message: plant cells—unlike animal cells—allow the passage of material from cell to cell, regardless whether they have primary cell walls or secondary cell walls.
Figure 35.8, Purves's Life: The Science of Biology, 7th Edition
Three Main Cell Types
Parenchyma
Most common cell type—the “typical” plant cell
Only have primary cell walls, which are thin and flexible.
Functions:
Photosynthesis (leaf parenchyma)
Starch storage (root parenchyma)
Collenchyma
Thicker primary cell walls, but no secondary cell walls
Main function: support
Sclerenchyma
Even thicker walls
Have secondary cell walls that are often strengthen with lignin.
Main function: support
They even provide support when they are dead.
Vascular Tissue
Two types of vascular tissue exist:
Xylem: transports water and minerals from roots to the stems and leaves.
