plant structure Flashcards
name the three different plant tissue systems
- dermal (outer)
- ground (middle)
- vascular (inner)
what is dermal tissue
- outer covering, epidermis
- cell type: epidermal
- function: skin, protection (waxy cuticle) and facilitate exchange (stomata)
what is ground tissue
- bulk of the plant, filling tissue
- cell type: parenchyma, collenchyma, sclerenchyma
- function: various, bulk of all plant tissues, support, leaves (photosynthesis)
what is vascular tissue
- plumbing system (similar to circulatory system)
- cell type: xylem (transports water from root to leaves) and phloem (photosynthetic products from leaves to roots)
- function: transport of materials
what are the types of cells in plants
- epidermal cells: ‘hairy’ (trap water, produce chemicals to deter a herbivore)
- parenchyma: pith, metabolic functions, synthesise / store photosynthetic products
- collenchyma: cortex, support young cells, flexible support
- sclerenchyma: skeleton, thick secondary cell wall (lignin), rigid, supporting elements
- water conducting (xylem): tracheids and vessel elements, tubular, elongated cells that are dead at functional maturity
- sugar conducting (phloem): sieve-tube elements and companion cell, alive
describe the generic structure of plant cells
- cell wall: structure and shape, strength (grow upwards, withstand gravity)
- chloroplasts: photosynthesis
- middle lamella: glue that holds cells together, made of pectin (jelling agent)
- central vacuole: turgid pressure
- plasmodesmata: junctions for communication and transport of nutrients, water and substances
what are plant cell walls made up of
- cellulose: glucose chains joined together by h bonds (highly effective, allow flexibility), elongation with plant, support, forms fibres, long fibrous threads
- layering of cell walls for strength (primary / secondary)
what is the primary cell wall
- first layer formed by a developing cell (seedling)
- flexible, allow extending as cell enlarges / matures
- can vary in thickness with thinner areas punctuated with plasmodesmata
- stains blue
- parenchyma (thin primary), collenchyma (thick primary)
what is the secondary cell wall
- forms as cell matures (tree), inner surface of primary
- higher cellulose content due to three distinct layers (inner middle and outer - grow individually over time)
- lignin: lignified, binds to cellulose, prevents degradation, pathogenic attacks, waterproofs, allows life forever, strengthens
- stains red
- sclerenchyma and xylem have well developed secondary cell walls (require lignin)
what are vascular tissue cells
xylem:
- perforated walls and pits to allow unimpeded flow of water from one cell to another
- water conducting cells, dead at functional maturity to allow efficient movement of water
- lignified secondary cell wall
- elongated cell, ‘pipe’, pits (connection / movement)
- large cells, contain tracheids and vessel cell
- requires more strength than phloem, no active transport (no companion cell)
phloem:
- sieve tubes (conducting cells) and companion cells (control sieve tube)
- transports sugar and photosynthesis products
- sieve tube: at maturity it is alive but it lacks a nucleus, cytoskeleton and ribosomes (efficient movement of sugars), alive because of companion cell
- companion cell: controls sieve tube, directly next to it, requires energy for regulation of active transport of movement of sugars
what two structures are dead at functional maturity, what does this mean
- xylem and sclerenchyma
- no longer growing or reproducing, caused by lack materials, only cell wall is left, cell contents have died, skeleton of the cell remains (cell wall)
- lignin prevents the plant from dying, mechanically breakdown (destroys unnecessary cells)
- xylem: empty cells so that water can move, ‘pipe system’, no contents, structural cell wall, highly efficient in transporting water
- sclerenchyma: only required as a bone system, doesn’t require energy and resources, required for support and structure
what is a cotyledon
- embryonic seed leaf
- leaf like structures inside a seed
- first photosynthetic leaves
- define the stem and root apex (direction of growth)
- define flowering plants into two groups, defined by embryonic development
what are the differences between a monocot and a dicot
- D: 2 cotyledons in seed, trees (bean, sunflower), seed broken into two, tap root system, epigeal germination (above ground)
- M: 1 cotyledon in seed, grass / corn, no mature growth, adventitious root system, hypogeal germination (underground)
describe stem morphology
- shoot tip (growth, apical meristem)
- node (leaves)
- internode (place between nodes)
- axillary bud (where leaves are forming)
- leaf and petiole
- apical meristem: actively divide and differentiate (specialised in structure and function), top of the plant, allows growth upwards
describe the structures of a monocot stem and a dicot stem
D:
- large central pith of parenchyma, cortex of collenchyma
- vascular tissue forms a single ring (xylem inside, phloem outside)
stem is circular, large pith in the middle of the stem
vascular tissue = bundles
- xylem inside, phloem outside
- vascular bundle = phloem and sclerenchyma
M:
- scattered vascular bundles (face; phloem = forehead, xylem = nose)
- no central pith, ground tissue
- epidermis surrounding outside
describe root morphology and monocot vs dicot
- roots grow underground, made up of a tap root (central), continuous tissue
- dicot: tap root with lateral roots, form off of other roots not just stem
- monocot: adventitious system, fibrous lateral root system, directly off of stem
describe the internal root structure and different zones
- central circular inner structure, well-developed cortex, inner vascular cylinder (stele)
- zone of cell division: mitosis, contains a meristem (actively dividing cells)
- zone of cell elongation: elongation to increase growth of root system, middle of root
- zone of cell differentiation: specialising of structure and function, top of root
what is a vascular cylinder (stele / root) and the difference in monocot and dicot
- takes in water from soil up plant to the leaves
- must have enlarged cortex region to regulate what enters the plant body
- dicot: star shaped core of xylem points (no pith), phloem surround
- monocot: xylem projections (bigger) alternating with phloem, central pith, does not meet in middle
what is a pericycle
- thin layer of cells from which lateral roots arise
- vascular cylinder
- root systems must come off of vascular tissue to produce new root tissue, actively divides (meristem)
what is the endodermis
- root system, stains red (no secondary wall)
- water movement in root system, developed cortex
- forces water to move through the symplastic pathway, water resistant cell walls
first point of contact with water, intake with water before it hits the xylem
describe the apoplastic and symplastic pathway
- apoplastic: intercellular space, cell walls, non-existing living space
- symplastic: water moves into the cells, across plasma membrane, regulation, allows cell to cell connection
what is the difference in leaf morphology / venation in monocot and dicots
- venation: how the veins are arranged
- M: parallel veins, no mid rib / vein, face, forehead (phloem), nose (xylem)
- D: net venation, prominent mid rib, xylem (above), phloem (below)
describe the leaf anatomy
- upper epidermis: cuticle to prevent water loss
- lower epidermis: high amount of stomata for gas exchange
- palisade mesophyll tissue: elongated long cells, upper side of leaf, compact, many photosynthesis chloroplasts
- spongey mesophyll: space between cells, widely dispersed, gas exchange, near stomata, lower side of the leaf
- stomata: pore with guard cells (open and close pore)
what are dorsiventral and isobilateral leaves
- D: upper and lower epidermis are different, palisade (rectangle) / spongey (circle) mesophyll
- I: upper and lower epidermis are the same, spongey mesophyll (circle), stomata are more developed on lower surface, cuticle more developed on upper, xylem is located on upper surface of the plant
what is primary growth
- apical meristem
- increase in vertical growth / shoot system / shoot tip
what is secondary growth
- dicots only (monocots lack cambium, growth not necessary)
- vascular cambium / bark: cork (external), cork cambium (internal) and secondary phloem, in vascular bundle, produces wood and bark, primary phloem / epidermis rupture / are compressed (cannot keep up with growth, dead at functional maturity )
- cork cambium: small layer beneath epidermis, produces protective cork
