Roots Module 4 Flashcards
What are the typical functions of roots?
anchorage, uptake of nutrients and water, storage (rhizomes), hormone production
Specialized functions in roots? Examples too.
brace roots - corn, banyon
air roots - fig (pneumatophores)
photosynthetic roots for anchorage - orchid
parasitic roots - dodder
Basic Structure of a root?
Root cap, Region of cell division, region of elongation, Region of maturation and differentiation.
What does the root cap do?
Protection of the growing apex as it pushes through the soil and produces mucilage to aid in movement. Also the preception of gravity (geotropism)
Region of cell division important
It’s where cell division takes place, located in the tip
Region of cell elongation
cell expansion and increase in length
Region of cell maturation and differentiation
where cells mature, increase in size, form root hairs and differentiate into different tissues
What makes up the epidermal tissue system?
Epidermis and root hairs
What does the epidermis do?
Offers protection, it has a waxy cuticle (prevent water loss), a pest barrier (fungi, nematodes)
Root hairs
Uptake of water and nutrients, but they are short lived not more than 2 weeks.
root hairs can be destroyed by fertilizer burn, and pests reduce number of hair, and they are susceptible to transplant shock
One 4-mos rye plant can have 14 billion root hairs, an absorbing surface of 401 cubic meters
What is the ground tissue system made up of?
Cortex and endodermis
What is the cortex?
Storage; for the needs of molecules or waste
the cells are alive
What is the endodermis?
inner boundary of the ground tissue system, they possess a special waxy substances in the cell wall (casparian strip)
forces nutrients and water to enter the cell through the plasmodesmata which are then filtered directly to the xylem.
What are plasmodesmata?
They are channels from the cytoplasm of one cell to the next cell.
What is the Vascular tissue system made up of?
The xylem, phloem, pericycle, and vascular cambium (only in dicots)
What is the xylem?
The transport of water and nutrients over long distances, only moves upwards towards the stem.
What is the phloem?
Transports the products of photosynthesis (sugars and starches) to all parts of the plant (can move up and down.
They possess many mitochondria for energy production and are a living tissue.
What is the pericycle?
Storage and the site of formation for lateral branches
Lateral branches in roots
They form from the pericycle
branches push their way through the side of the root
lateral branches have the same structure as primary roots
The vascular systems between primary and lateral roots are connected
Tap Root Systems
One main root (radicle) with many lateral branches
found in DICOT
ex soybean, vegetable root crops, tree species, flowers
Fibrous Root Systems
many form from close to the shoot (stem) with many lateral branches
found mainly in MONOCOTS
ex corn, pasture grasses, turf, rice, bamboo, banana, and palm
Fibrous roots VS Taproots
Water requirements differ; taproots can penetrate hard soil, fibrous do better in less compacted soil.
taproots are better at taking up deep water, dicots are water loving
monocots grow in drier environments
Root Associations
Rhizobium and Mycorrhizae
What is Rhizobium?
Most common legume association with the bacteria
a symbiotic relationship; plant gives bacteria 40% of it’s energy, nodules form and produce a fixed nitrogen for the plant
What is Mycorrhizae?
an association between plants and fungi, different plants to different fungi, not a clear symbiosis
Mycorrhizae are thread ;like structures that wrap around the roots and root hairs
The fungus breaks down complex molecules into simple molecules for the plant, like phosphorus, they also create more surface area for nutrient uptake.
