Plant structure & growth Flashcards
What are the 3 basic plant organs?
Roots
Stems
Leaves
What are the 3 basic plant organs organised into?
Root & shoot systems
What are the 3 functions of roots?
> anchoring plant
absorbing minerals & water
storing carbohydrates
What is the primary root?
The 1st root (& organ) to emerge from a germinating seed
Describe the root system of eudicots & gymnosperms
Taproot system:
> a taproot = main vertical root
> lateral roots = arise from taproot
Describe the root system of monocots
Fibrous root system:
> adventitious roots = arise from stems/leaves
> lateral roots = arise from adventitious roots
Where does absorption of water & minerals occur in most plants?
At or near root hairs
- increase SA
What are the examples of root adaptations w/ specialised functions?
> prop roots > buttress roots > 'strangling' aerial roots > pneumatophores > storage roots
What is the function of prop roots?
Support tall, top-heavy trees in sandy soils
e.g. Hala trees in south pacific
What is the function of buttress roots?
Prevent trees falling over which have v shallow root systems
e.g. in tropical forests w/ nutrient-poor soil
What is the function of ‘strangling’ aerial roots?
Why are they ‘strangling’?
Seeds can germinate in branches of tall trees
–> send aerial roots to the soil
Shading from leaves of new plant kills the host tree
What is the function of pneumatophores?
Obtain O2 from air as thick estuarine mud lacks O2
- negatively geotropic roots
e.g. Mangroves
What is the function of storage roots?
Store water & sugar
e.g. sugar beet
What do stems consist of?
Alternating system of nodes (= points where leaves attach)
& internodes (= segments between nodes)
What is an axillary bud?
A structure that has the potential to dorm a lateral shoot or branch
What is an apical bud?
(AKA terminal bud)
Located near shoot tip & causes elongation of a young shoot
What are the examples of modified stems?
> rhizome
stolons
tubers
bulbs
What are rhizomes?
Horizontal shoots that grow just below surface
e.g. Iris
What are stolons?
Horizontal shoots that grow along soil surface & allow asexual reproduction of platelets at nodules along stolon
E.g. strawberry plants
What are tubers?
Enlarged ends of rhizomes/stolons
Used for storing food
(the ‘eyes’ on potatoes are axillary buds)
What are bulbs?
Vertical underground shoots that store food
E.g. onion
What do leaves generally consist of?
A flattened blade & a petiole (=stalk)
- joins leaf to node of stem
How do monocots & eudicots differ in the arrangement of veins in leaves?
Monocots = parallel veins
Eudicots = branching veins
What are the 3 types of leaf shape?
Simple
Compound
Doubly compound
What are the examples of modified leaves?
> tendrils > spines > storage leaves > reproductive leaves > bracts
What are tendrils?
What is different about grapevine tendrils?
Leaves that support plants e.g. pea plants use to cling to objects
Once attached tendril coils & pulls plant closer to support
They’re modified stems NOT leaves
Give an example of spines
Spikes on a cactus
Photosynthesis carried out in fleshy green stem
Give an example of a storage leaf
In ice plants they store water