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
