Roots

Root Functions

1. Water Uptake for evaporative cooling, etc.
2. Mineral Uptake from soil
3. Conduction of water and minerals to rest of plant
4. Storage of nutrients - especially starch, sugars, minerals, others; particularly in winter, then moved up in sap flow--Maple Syrup!
5. Anchorage of plant- growth of roots through soil
   1. Tap root - resists blowdown of tall trees in wind, poor uprooting resistance
   2. Fibrous roots - plants blow down easily (does it matter?), fabulous uprooting resistance (grazing pressure)
      Many plants have a compromise!
   3. Buttress roots - tropical plants have roots expanded vertically to create "buttress" along top of ground and ridge up the trunk. Seen in Jurassic Park.
   4. Prop roots - adventitious roots from stem angle down and out much like a "flying buttress".
6. Legume nodules - Rhizobium bacterial symbiosis, nitrogen fixation
7. Orchid velamen (aerial roots) - water absorption, nutrient capture, etc.
8. Black mangrove (Avicennia nitida) pneumatophores - gas exchange for roots in microaerobic swamp muck
9. Gravitropic response - root cap perception, growing zone positive response to gravity vector...formerly geotropism (why abandoned?).

Root Origin

1. Root Cap - cell cluster at tip of root responsible for gravitropic detection, cell sloughing, mucigel secretion. Have you licked mucilage? Lubrication of soil channel.
2. Quiescent Center - zone with little observable activity, source of new cells for ...
3. Zone of cell division - meristematic cells, cell cycle
4. Zone of cell elongation - small cells enlarge and elongate pushing root tip through soil
5. Zone of cell maturation - phloem, xylem mature...root hairs appear from epidermis

Root Structure/Function

1. Root Hairs - cell extensions of epidermis increase absorptive surface
2. Epidermis - water and non-selective mineral intake via root hairs
3. Cortex - storage parenchyma (starch, sugar, etc.)
4. Endodermis - selective mineral pump (concentrates particular minerals as it pumps them into xylem area)
5. Pericycle - origin of lateral roots in young areas, bark on older roots
6. Vascular Cylinder
   1. Phloem - conducts nutrients from leaves
   2. Cambium - makes wood-woody plants only
   3. Xylem - conducts minerals and water up

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