Organs and Tissues Flashcards
What does a plants structure reflect?
Its interactions with the environment of two time scales (over the long term and short term).
How do plant structures reflect interactions with the environment over long term?
Natural selection causes species to accumulate morphological adaptations that enhance survival and reproductive success.
How do plant structures reflect interactions with the environment over short term?
Over short term, plants exhibit structural responses to their specific environments.
(eg. feathery leaves to enhance uptake of CO2)
What type of response is even faster than the short term response?
A physiological (functional) response/adjustment.
- eg. releasing a hormone which causes the stomata to close
What are the three basic organs of plants?
1) roots
2) stems
3) leaves
What is an angiosperm?
a flowering plant
What are the principal division of angiosperms?
1) monocots
2) dicots
What is special to monocots?
EMBRYOS: one cotyledon
LEAF VENATION: parallel venation
STEMS: vascular bundles randomly allocated
ROOTS: fibrous root system
FLOWERS: multiples of 3
What is special to dicots?
EMBRYOS: two cotyledons
LEAF VENATION: netlike venation
STEMS: vascular bundles arranged in a ring
ROOTS: taproot is present
FLOWERS: multiples of 4 and 5
What are the two places where plants inhabit their resources? What comes from each specific resource?
1) SOIL: water and minerals
2) AIR: CO2 and light
What two systems have plants evolved?
1) a subterranean (underground) root system
2) aerial shoot system
Are the two systems (root and shoot) independent of each other? Why?
No, both systems depend on each other.
- roots (lacking chloroplasts, living in the dark, not obtaining sugars from photosynthesis) would starve,
- shoot systems (reproductive tissue, flowers, etc.) depend on water and minerals absorbed from the soil.
What are the primary roles of the root system?
- anchor the plant in the soil
- absorb minerals and water
- store food
What does a fibrous root system allow monocots to do?
extend its (the plants) exposure to soil water and minerals, as well as anchor it to the ground.
What does a taproot root system allow dicots to do?
- anchor the plant
- store food
- support flowering
- support fruit production
Where does most water and mineral absorption take place?
in the root tips
What increases the roots surface area?
root hairs
What are root hairs?
Root hairs are extensions of individual epidermal cells on the root surface.
What are “adventitious” roots?
roots which arise above ground from stems or leaves.
What are roots called which arise above ground from stems or leaves?
adventitious roots
What is the purpose of an adventitious root?
props which help support tall stems.
What does a shoot consist of?
stems and leaves
What are the two types of stems?
1) vegetative (leaf bearing)
2) reproductive (flower-bearing)
What is a stem?
- a system of nodes (the points at which leaves are attached),
- a system of internodes (stem segments between nodes)
What is an axillary bud?
the part of the plant located at the angle by each leaf and stem, with the potential to form a vegetative branch.
What has the potential to form a vegetative branch?
an axillary bud.
Where is the growth of a young shoot usually located?
at its apex (where there is a terminal bud with a developing leaves, and developing nodes and internodes)
What is a terminal bud?
a part of the plant with developing leaves and a compact series of nodes and internodes.
- special tissue called meristems (undifferentiated cells which produce vegetative and reproductive organs).
What are meristems?
undifferentiated cells ( can divide indefinitely and produce all differentiated tissues) which produce vegetative and reproductive organs.
What are the undifferentiated cells called in plants?
meristems
What is apical dominance?
the presence of a terminal bud is partly responsible for inhibiting the growth of axillary buds.
What does a plant manage to do by concentrating resources and growing taller?
apical dominance increases the plants exposure to light.
What happens when a plant lacks a terminal bud?
the axillary bud break dominance and gives rise to a vegetative branch complete with its sown terminal bud, leaves and auxiliary buds.
What are some examples of modified shoots? What are modified shoots?
- modified roots are not roots, they are shoots
eg. - stolons,
- rhizomes,
- tubers,
- bulbs
What do stolons allow for? Example of plant.
stolons, “runners”, grow on the surface and allow plants, such as strawberries to colonize large areas asexually, when a parent plant fragment is greater than the offspring.
What are rhizomes?
horizontal stems that grow underground (ie. ginger).
What are tubers?
swollen ends of rhizomes specialized for food storage (eg. potatoes).
What are bulbs?
vertical, underground shoots consisting mostly of swollen bases of leaves that store food (eg. onions).
What is the function of leaves?
Leaves are the main photosynthetic organs of most plants.
What can photosynthesise in plants?
leaves and green stems
What do leaves consist of?
1) flattened blades
2) a stalk (the PETRIOLE) (joining the leaf to a stem node)
What do plants develop in the absense of petrioles? Where does this occur?
the base of the leaf forms a SHEATH that envelops the stem.
this occurs mainly in monocots.
How to taxonomists classify plants?
besed on:
- leaf shape
- spacial arrangement of leaves
- pattern of veins
What are the different types of leafs?
1) SIMPLE leaf: single, undivided blade
2) COMPOUND leaf: several leaflets attached to the petiole.
What are examples of modifications of plant leaves?
- cactus spines
- tendrils for support
- leaves modified for water storage
- brightly coloured leaves attract pollinators
What is a tissue?
a group of cells that preform a similar function
What are the three tissue systems which plants are composed of?
1) dermal tissue
2) vascular tissue
3) ground tissue
What is dermal tissue? What is the primary dermal tissue called?
primary dermal tissue = EPIDERMIS
- single layer of tightly packed cells
- covers and protects the younger parts of the plant
- can form extentions of epidermal cells near the root tips
- can secrete a waxy coat (CUTICLE), helping the aerial parts of a plant to retain water.
What is the waxy cuticle of plants called?
the cuticle
What is dermal tissue? What is the secondary dermal tissue called?
secondary dermal tissue=PERIDERM
- multilayer that replaces the epidermis during growth in the thickness of stems and roots.
- after accumulation the periderm forms the outer bark in trees
What are the differences and similarities between the epidermis and periderm?
epidermis:
- flat cells
- thick cell walls
- waxy cuticle
- function: protect young plants
periderm:
- waterproof cells
- thick cell walls
- dead at maturity
- function: forms outer barks in trees
What is vascular tissue in plants? What is it composed of? What does each section do?
Vascular tissue is involved in the transport of materials between roots and shoots.
1) XYLEM: transports water and dissolved materials upwards from the root to the shoot.
2) PHLOEM: transports food made in mature leaves through photosynthesis to the roots and non-photosynthetic parts of the shoot system.
What does the xylem consist of?
1) TRACHEIDS: long, thin cells with narrow ends. moves water through pits.
function: transport and support.
2) VESSEL ELEMENTS: wider, shorter, thinner-walled, less narrow ends. aligned end to end.
function: allow for water flow due to perforated ends
- elongated cells
- dead at functional maturity
- both have interrupted pits
- fully specialised for their function
Label a transection of a vascular bundle.
- cork
- xylem tissue
- cambium
- phylum tissue
- pith
How are the secondary walls of xylem hardened?
with lignin
What occurs in the phloem? What cells is it composed of?
- sucrose, organic compounds, and mineral ions move throughout tubes formed by sieve tube members
- composed of:
1) SIEVE TUBES: - lack nucleus, ribosomes and vacuoles. facilitate fluid flow.
2) COMPANION CELLS: assist the sieve tube cells.
What is the function of the pith?
store sugars and proteins
What is the function of the cortex and epidermis?
protect the stem
What is ground tissue?
tissue that is neither dermal or vascular tissue.
What is the ground tissue in dicot stems? What is it divided into?
1) PITH: internal to vascular tissue
2) CORTEX: external to vascular tissue
What is the function of the ground tissue?
- photosynthesis
- storage
- support
What are the three basic types of cells in plants?
1) PARENCHYMA CELLS
2) COLLENCHYMA CELLS
3) SCLERENCHYMA CELLS
What are protoplasts?
- plant cells that have had their cell walls removed by treatment with cellulolytic enzymes
- the cell contents exclusive of the cell wall.
What are parenchyma cells?
- primary flexible walls
- thin and flexible
- lack secondary walls
- preform most metabolic functions (synthesize and store organic products)
- “typical” plant cell because it is LESS SPECIALIZED
EXCEPTION:
- highly specialised sieve-tube members (of the phloem) are parenchyma cells
NOTES:
- fleshy part of fruit=parenchyma cells
- colourless plastids store starch
- can contain chloroplasts
- it is possible to regenerate an entire plant from a single parenchyma cell
What are developing plant cells before specializing?
parenchyma cells
What happens to unspecialized adult parenchyma cells?
- they do not undergo cell division,
- retain their ability to divide and differenciate into other cell types
What are collenchyma cells? What are their major characteristics?
- thicker primary walls (UNEVENly thick)
- grouped into strands or cylinders
FUNCTION:
- help support young parts of the plant
What are sclerenchyma cells? What are their major characteristics?
- thick secondary wall (strengthened by LIGNIN)
- more rigid
- cannot elongate
- occur in plant regions that have stopped growing (lengthening)
- dead at functional maturity
FUNCTION:
- support elements of the plant
- produce rigid secondary walls before the protoplast dies
How can sclerenchyma cells enable cell wall stretching?
they create a spiral or ring pattern in growing plants
What are vessel elements and tracheids in the xylem?
sclerenchyma cells
What are the two other types of sclerenchyma cells?
1) FIBERS:
- long, slender, tapered
- occur in groups
2) SCLEREIDS:
- shorter
- irregular
- harden nutshells, seed coats and the gritty texture to pear fruits.
What is a major difference between plants and animals?
growth and development in plants is not just limited to the embryonic and juvenile period but occurs throughout the whole life of the plant.
What does a typical plant consist of?
embryonic organs, developing organs, and mature organs.
State the functions of parenchyma cells, collenchyma cells and sclerenchyma cells.
PARENCHYMA CELLS:
- photosynthesis
- secretion
- storage
COLLENCHYMA CELLS:
- support leaves and stems
SCLERENCHYMA CELLS:
- support
