Vegetative Growth-roots Flashcards
What are five functions of roots?
- Absorption of water and nutrients
- Anchorage of the plant
- Storage of nutrients and carbs
- Transport
- Propagation
Seminal roots
Derived from seed.
Radicle of seed becomes primary root
Secondary root branches off primary root
Adventitious Roots
Derived from tissues other than the root, usually from the stem
Epidermis
Includes root hairs; absorbs water and nutrients and provide a layer of protection
Cortex
Storage; diffusion of water and nutrients
Endodermis
has Casparian strip; all water and nutrients must go through cells
Stele
pericycle + vascular cylindar
Pericycle
Meristematic; lateral root development
Vascular cylinder
xylem and phloem
- x conducts water and nutrients
- p conducts food and metabolites
- Vascular cambium- meristematic tissue between x and p; increases root girth
- pith: center part of cylinder in monoctos
Seminal or seed roots of corn
Arise from first node along with radicle.
Scutellum (cotyledon) remains in the seed.
Seminal roots help seedling, but nodal roots take over.
Nodal or Adventitious (or Corwn) roots of corn
Emerge from lower nodes (usually five nodes remain below ground) often called the crown.
Important for water and nutrient uptake (and support)
Brace or Prop roots of corn
Aerial rots, emerge from nodes just above soil surface.
Provide support and take up water and nutrients.
Does deeper planting encourage deeper rooting in corn?
Depth of seminal root system is influenced by seedling depth.
But crown of plant (where nodal roots develop) is not influenced much by seeding depth
- mesocotyl elongates during emergence
- as coleoptile nears soil surface, ratio of red to far red light affects supply of growth hormones from coleoptile to mesocotyl
- mesocotyl stops elongating
- crown is usually able 1/2 to 3/4 inch deep for seeding depths of 1 inch or more
root nodules
Symbiotic association between legume and Rhizobium bacteria.
Different strain of Rhizobium for each legume species.
Bacteria fix atmospheric N for plants
Plants provide nourishment for bacteria.
Four crop management practices related to roots
- Depth of irrigation
- Plants vary in root depth and spread
- need to provide water to root zones - In-crop cultivation
- some crops are cultivated to control weeds
- shallow-rooted crops can be damaged - Tillage
- deep-rooted crops need deeper tillage and less subsoil compaction
- shallow rooting predisposes plants to root lodging - Fertilization and fertilizer placement
- deep-rooted plants benefit from deeper placement of fertilizer
- Phosphorus promotes good rooting
