Test 2 Flashcards
Lectures 3 & 4
Why are plants important?
- Plants supply food.
- Plants maintain the atmosphere.
- produce oxygen and absorb carbon dioxide during photosynthesis
- oxygen is essential for cellular respiration for all aerobic organisms
- maintains the ozone layer that helps protect Earth’s life from damaging UV radiation
- removal of carbon dioxide from the atmosphere reduces the greenhouse effect and global warming - Plants recycle matter in biochemical cycles.
- plants such as pea’s host on bacteria that fix nitrogen
- this makes nitrogen available to all plants, which pass it on to consumers - Plants provide many products.
- Plants create habitats for many organisms.
What is the environment and conditions of a shoot system?
Environment - above ground, thin, gaseous
Conditions - low water, fluctuating light, wind, heat, UV exposure
What is the environment and conditions of a root system?
Environment - below ground, dense, soil based
Conditions - water often available, patchy resources, many pathogens
What is determinate growth?
Determine Growth
- growth with defined limits
- occurs in most animals and some plant organs eg. most leaves
- growth stops once a certain size is reached
What is indeterminate growth?
Indeterminate Growth
- no defined growth limit
- continuous growth throughout a plant’s life (except during dormancy)
- plant has embryonic, developing, and mature organs at all times
What is a meristem and what is its function?
Meristem
- perpetually embryonic tissues in plants
- enable indeterminate growth
- sites for new cell formation, growth and differentiation
Where are apical meristems found?
At tips (apices) of shoots and roots.
What are apical meristems responsible for?
Primary growth - lengthening of the plant
What does the lateral meristem consist of?
The vascular cambium and cork cambium.
What are lateral meristems responsible for?
Secondary growth - thickening of stems and roots.
- present in all gymnosperms and most eudicots
- rare in monocots
What is the first step of cell division for meristems?
Step 1: One meristem cell divides, producing……
- one differentiated cell (which will develop into specialised tissue)
- one remaining meristem cell (to continue dividing)
What is the second step of cell division for meristems?
Step 2 and Beyond: this process continues, with each cell division producing a new differentiated cell and maintaining the population of meristem cells
What protection features are in place to protect apical meristems?
Apical meristems can be dormant in buds, which is important if the Shoot Apical Meristems (SAM) gets damaged or eaten.
What is the leaf primordia?
Protects the shoot apical meristem.
What is the root cap?
Protects the root apical meristem.
What is the vascular cambium?
Produces secondary xylem - the main component of wood.
What is the cork cambium?
Produces the outer bark.
What is dermal tissue?
- outer protective covering, known as the epidermis
- usually one cell layer thick
What are epidermal cells?
- main cells in the epidermis
- transparent, most lack chloroplasts
What are guard cells responsible for?
- regulating the opening and closing of stomata
- present shaped, contain many chloroplasts
What are palisade mesophyll?
Photosynthetic cells found just below the epidermis (in leaves).
What are spongy mesophyll?
Cells involved in gas exchange (in leaves).
What are trichomes?
- hair-like structures that grow from the epidermis to protect or aid in water retention
- cool leaf surfaces and reduce evaporation
- cover stomatal openings to limit water loss
- some are glandular and secret substances to deter herbivory
What are root hairs responsible for?
- increase root surface area for water and nutrient absorption
- may be covered by a fatty cuticle (a waxy coating) in some plants to reduce water loss
What is stoma?
Regulates gas exchange and water evaporation in leaves by forming an opening, allowing oxygen, carbon dioxide, and water vapour to pass.
What is the stele?
The central part of the plants vascular tissue, made up of xylem and phloem.
What is xylem and its function?
- transports water and dissolved minerals from roots and leaves
- main water conducting tissue in vascular plants; made of dead, hollow tubes that support the plant
What is phloem?
Transports sugars and amino acids between sources eg. leaves and sink, growing roots/tips, seeds/fruit tissues.
What are the two cell types in xylem?
Tracheids and Vessels
What are tracheids?
Overlapping, open ended, with small holes in their walls for water transfer.
What are vessels?
Advanced, non tapered, cells arranged end-to-end; water moves through perforation plates.
What are some features of both cell types in xylem?
- both types have spiral lignin for strength
- lignified xylem forms wood
What are the two types of elongated cells in phloem?
Sieve cells and sieve tube members (STM).
What are sieve cells?
- found in seedless vascular plants and gymnosperms
What are sieve tube members (STM)?
- found in angiosperms (more specialised and efficient)
- lack a nucleus, associated with companion cells
- sieve plate separates sieve tube members
What is ground tissue?
Found throughout the plant; responsible for photosynthesis, storage, and structural support.
What are the three types of ground tissue?
Parenchyma, collenchyma, and sclerenchyma.
What are features of parenchyma?
- metabolism, synthesis, storage, thin walls, large vacuoles, and abundant
What are features of collenchyma?
- flexible support for growth, elongated with unevenly thickened walls
What are features of sclerenchyma?
- structural support, dead at maturity, rigid, thick walls (lignin), two types
What are the functions of roots?
- Anchor the plant in the soil
- Absorb water and nutrients from the soil
- Store food and nutrients eg. carrots
- Reproductive clones (some plants can produce new plants by sprouting from their roots)
What are the two types of root systems?
Taproot System and Fibrous Root System
What is a taproot system?
Single large root with smaller brach roots.
What is a fibrous root system?
Many small roots of similar size.
What is the terminal bud?
Extends the shoot system (contains the shoot apical meristem - SAM).
What is the axillary bud?
Develops into branches or flowers (also contains shoot apical meristems, may be dormant).
What is the node?
The point where the leaf attaches to the stem.
What is the internode?
The segment of step between two nodes.
What is the function of leaves?
- photosynthesis
- gas exchange, water loss (transpiration), and food storage
What is a simple leaf?
One leaf blade attached to the stem.
What is a compound leaf?
A leaf divided into multiple leaflets.
What’s the blade?
The flattened part of the leaf, responsible for photosynthesis.
What is the petiole?
The stalk that attaches the leaf to the stem (not all leaves have a petiole).
What are the veins?
Vascular bundles in the leaf containing xylem and phloem.
What are cuticles?
Waxy layer covering the epidermis.
What’s the leaf surface of eudicots?
Have a network of branched veins.
What’s the leaf surface of monocots?
Have parallel veins.
What are flowers?
Modified stems bearing modified leaves.
What are pedicels?
The stalk of the flower, which leads to the bud.
What are receptacles?
Expanded tips of the pedicel where flower parts attach.
What are whols?
Flower parts arranged in circles.
What are sepals?
Outermost whorl, protective layer.
What are petals?
Second whorl, often colourful to attract pollinators.
What are stamens?
Third whorl, male reproductive organs.
What are filaments?
Stalk of the stamen.
What are anthers?
Pollen bearing part.
What is pollen?
Male gametophyte
What are carpels/pistils?
Innermost whorl, female reproductive organs.
What is the ovary?
Contains ovules, later becomes the fruit.
What is the style?
The neck or stalk.
What is the stigma?
The tip where pollen lands.
What are ovules?
Female gametophytes (embryo sac)
What is bulk flow?
Water and nutrients move through the plant via bulk flow, involving both pulling and pushing mechanisms.
What is transpiration?
The evaporation of water from plants leaves, leading to water loss.
What is the process of water absorption?
- Root hairs absorb water
- Movement to vascular tissues
- Water moves into xylem
- Water exits the plant
- Mycorrhizal fungi aid absorption
What is carbohydrate movement?
Carbohydrates produced in the leaves through photosynthesis are transported up and down through the phloem to other parts of the plant.
What are the three transport routes through cells?
Apoplast, symplast and transmembrane.
What is the apoplast route?
Water moves through cell walls and spaces between cells, bypassing membranes.
What is the symplast route?
Water travels through cytoplasm between cells , connected by plasmodesmata.
What is the transmembrane route?
Water moves across membranes of cells and vacuoles, offering the greatest control for the plant.
How do plants combat water loss?
- waxy cuticle and wooly trichomes
- reduced stomata
- stomata in pits
- dormancy
- leaf loss
What is alternation of generations?
Plants alternate between two different life stages, or generations, in their life cycle; a haploid stage called gametophyte and a diploid stage called sporophyte.
What are bryophytes?
The dominant gametophyte generation, small sporophyte produces spores by meiosis.
What are lycophytes and pterophytes?
Seed plants; similar to lycophytes/pterophytes but with separation of male and female parts, producing pollen and ovules.
What are angiosperms?
Dominant sporophyte generation, tiny gametophyte inside the ovary and pollen grain.
What is pollination?
The process where pollen is placed on the stigma.
What is self-pollination?
Occurs when pollen from a flower’s anther fertilises the stigma of the same flower or another flower on the same plant.
What is cross-pollination?
Happens when pollen from one plant fertilises the flower of a different plant.
What are the evolutionary strategies for out-crossing?
- Operation of stamens and pistils
- Dioecious plants (males or females, not both)
- Self-incompatibility prevents self-fertilisation
- Dichogamy (stamens and pistils mature at different times)
What are the four types of pollination?
- Water
- Wind
- Animal
- Insect Pollination
Describe the relationship of coevolution between plants and pollinators?
- leads to physical traits that improve pollination success (pollination syndrome)
- plants attract specific pollinators to ensure pollen transfer between flowers of the same species
- pollinators are herbivores that visit flowers for food, not for pollination
- plants offer rewards to pollinators such as nectar, pollen, oils and scents
Explain fruit development
- fruits are defined as mature ovaries
- during seed formation, the ovary begins to develop into the fruit
- fruits can sometimes develop without seed development, as seen in bands, which are propagated asexually
Describe seed dispersal
- is the movement of seeds around the landscape
- plants must be adapted to the vendors (biotic and abiotic) they rely on for dispersal
- seeds and fruits very in shape to suit different dispersal methods
- dispersal is spatially and temporally variable, depending on the mechanisms and vectors involved
- most plants have evolved strategies to enhance their dispersal
What is seed dispersal syndromes?
- are morphological characteristics of seeds that correlate with specific dispersal agents
- these characteristics help seeds adapt to certain dispersal methods
