Root Morphology4 Flashcards
(22 cards)
Root Functions (4)
-Anchor plants in soil
-absorb water and minerals from soil
-conduct water and minerals to and from shoots
-Area for storage
1.Root cap
-protective layer of cells produced from root tip
-protects apical meristem
-constantly replaced by more cells from meristem
-gravity & amyloplasts result in downward growth
2.Region of cell division
-directly behind root cap
-include apical meristem
-cells divide every 12-36 hours
- cell elongation
-above region of cell division
- cells elongate causing roots to lengthen
4.cell maturation
above region of cell elongation
-primary tissues mature into secondary
-root hairs are formed
the 3 root tissues
epidermis
Cortex
Endodermis
Epidermis (5)
-Outer absorbing layer
-single layer
-covers entirety of root except root cap
-usually lacks stomata and cuticle
-absorbing surface increased through root hairs
Cortex(
-large thinned cell walls, above epidermis
-occupies greatest area in primary roots
-food storage
-loosely packed to allow water and minerals to flow through
Symplastic
travelling through living cells (cytoplasm)
apoplastic
through cell walls and intercellular spaces
-50% less resistance
hypodermis, and what its lined with
outermost layer of cortex,
protective, lined with suberin(slows loss of water)
Endodermis
-inner to cortex
-single layer cells
-boundary between cortex and vascular cylinder
-tightly packed cells
casparian strip
the border of the endodermis
creates a barrier for substances within roots
DICOT roots
-xylem forms star shape core with phloem bw arms of xylem
-pericycle
Pericycle
-one or more layers of cells surrounding vascular tissues in DICOT roots
-from which branch roots and lateral roots arise
-generates vascular cambium b/w xylem and phloem
MONOCOT roots
-ring of alternating bundles of xylem and phloem surround pith
-no vascular cambium
Pith
ground tissue in center of root
-spongelike
Mycorrhizae fungi
-assosiation is mutualistic w plants
-roots, facilitate nutrient acquisition
concentrates phosphorus
-facilitate N and micronutrients such as zonc and copper
-plant gives sugar and amino acids to mfs
-lots of woody species have these
Ectomycorrhizae
mycorrhizae grow between cell walls
more common
Endomucorrhizae
penetrate cell walls
Rhizobium bacteria
what family are associated with these?
produces nitrogenases to convert nitrogen to nitrates and other substacnes
-legume familly associated w these
-plant provides “food and lodging”(root modules)-less oxygen
what is produces in root modules?
leghemoglobin-binds to o2, allowing low enough o2 for nitrogenases to function , but high enough for bacteria life
