1
Q
What are some features of plants?
A
- unique tissues and organs
- rigid cell walls: contain cellulose, making that one of the most abundant plant-derived molecules on Earth
- chloroplasts (with chlorophyll)
- vacuoles (not seen in animals cells)
2
Q
Three things only found in a plant cell
A
- Chloroplast - contains chlorophyll, photosynthesis takes place here
- Vacuole - stores water, salts
- Cell wall - composed of cellulose
3
Q
Cuticle
A
- protective hydrophobic outer waxy layer on leaves
- covers the epidermis
- reduces water loss
- shields against UV radiation and provides mechanical support
4
Q
Cell wall
A
- multi-layered structure
- protects cell
- composed of cellulose
5
Q
Middle lamella
A
- separates primary and secondary cell wall
- holds cells together
- contains pectin and calcium
6
Q
Plasmodesmata
A
- cytoplasmic connections between cells
- they allow communications and signals to occur between cells and transport of materials
7
Q
Cellulose
A
- made up of glucose molecules forming a long chain
- glucose makes fibres
- primary structural component of cell wall
8
Q
Lignin
A
- makes cell wall strong and rigid
- strengthens cell wall
9
Q
Components of the cell wall
A
- middle lamella
- primary cell wall: hemicellulose, pectin, cellulose microfibril, soluble protein
- plasma membrane
10
Q
Primary cell wall
A
- contains cellulose (long chain of glucose molecules)
11
Q
Secondary cell wall
A
- has hemicellulose and lignin
- provides cell wall strength and thickening
- makes plants rigid
12
Q
Secondary growth seen in trees is due to?
A
- thickening of the secondary cell well
13
Q
Whole plant structure (label and draw)
A
Shoot system:
- reproductive shoot (flower)
- apical bud
- node
- internode
- axillary bud
- vegetative shoot
- leaf: blade, petiole
- stem
Root system:
- taproot
- lateral (branch roots)
(provides huge surface area)
14
Q
Functions of leaves
A
- primary site for photosynthesis when sugar is formed from CO2 and H2O and O2 is produced
- simple or compound in structure
- upper epidermis and lower epidermis (in between are mesophyll cells - palisade mesophyll and spongy mesophyll)
- cuticle on surface containing waxes (hydrophobic) that reduces water loss (transpiration)
15
Q
Adaptations of leaves to changing environments
A
- spines (on cactus): modified leaves, conserves water
16
Q
Functions of stems
A
- provide physical support to the plant
- involved in movement of water and nutrients up the plant through vascular system (xylem and phloem)
- allows for continued growth through the apical meristem
- contains axillary buds that give rise to side shoots
- used for storage of food and water
- allow for lateral growth to increase width of the stem
17
Q
Stoma(ta)
A
- absorbed CO2 for photosynthesis and release O2
18
Q
Veins
A
- are vascular tissues (xylem and phloem)
- transport system (water, nutrients, sugars), circulation
19
Q
Shoots grow through?
A
- apical buds and axillary buds
20
Q
What is an apical meristem?
A
- region of actively dividing cells that allows more growth (up or down)
21
Q
Rhizomes
A
- modified stem
- can be found in ginger, turmeric, ginseng plants
- used for storage of nutrients
22
Q
Tubers
A
- modified stem that has little nodes which has axillary buds
- e.x. potatoes
- produces shoots
23
Q
Bulbs
A
- modified stem with storage leaves
- ## e.x. onions
24
Q
What are the four types of meristematic tissues?
A
- Apical shoot - makes stem taller
- Apical root - make roots grow
- Axillary meristem - makes plant grow bushier
- Lateral meristem (vascular) - a meristem in a stem that makes the stem wider
25
What are meristems?
- actively growing regions found at the tips of shoots and roots of plants that allow for continued growth
- growth of side shoots from stems is also due to axillary bud meristems
- expansion of width stems (lateral growth) is also due to the activity of lateral meristems, especially cambium
26
Functions of roots
- to anchor the plant/tree in the soil
- to absorb water and nutrients from the soil
- roots have a large surface area due to root hairs
- continued growth occurs through the root meristems
- roots can be used for storage of nutrients
27
Types of roots
- prop roots: stabilizes large trees
- buttress roots: help stay upright
- "strangling" aerial roots: forms in the air to anchor the tree
- pneumatophores: specialized aerial roots emerging from water
- storage roots: underground roots acting as storage organs e.x. beets, carrots
28
Tissue types in plants
1. Dermal - found on the outside layer of the plant tissues, provides protection to the plant e.g. epidermis
2. Meristematic - found at the growing tips, used for extra growth (up, down, sideways)
3. Ground - three types: parenchyma, collenchyma, sclerenchyma
4. Vascular - two types: xylem and phloem
29
Parenchyma cells
- most common type
- these cells are found in leaves, tubers
- living cells
- involved in producing sugar during photosynthesis
- can store food (starch) eg. in roots, tubers, fruit
- have thin walls and large vacuoles
30
Collenchyma cells
- don't store food
- living cells
- have a function that is part of providing structural support to plants
- have thick walls
31
Sclerenchyma cells
- hollow, nonliving support cells
- thick-walled
- function: provide support and rigidity to plants
- aren't in most foods because it's too tough (like wood)
32
Xylem cells
- carries water and nutrients that enter the plant in the root up through the stem and out of all parts of the leaf
- consists of cells called tracheids and vessel elements which have pores in them and these cells are non-living
- like a plumbing system of the plant
33
Phloem cells
- runs parallel to the xylem and carries sugar that is produced in the leaves, dissolved in fluid, to all parts of the plant
- consists of sieve tube elements and companions cells and are living
34
Vascular cambium
- a ring of actively dividing cells found separating the xylem and phloem
- cell division result in the formation of the secondary xylem and secondary phloem
- continuous division over the years caused formation of secondary xylem (= wood) in larger trees
- these result in the formation of "growth rings" seen in large trees
- permits secondary (lateral) growth
- growth rings in trees due to the activity of vascular cambium
35
Plants need:
- need water and nutrients in order to grow and survive
- they produce their own carbon source (glucose) through photosynthesis
- need carbon dioxide from the air (so they release O2)
- therefore, plants have evolved mechanisms and can be adapted to survive under dry conditions
36
Coniferous v.s. Deciduous Trees
Coniferous trees: have broad, flat leaves that drop seasonally (lose leaves in the winter)
Deciduous trees: have small, needle-like leaves that retain year-round
37
Water movement from soil to top
1. Water in the soil
2. Root hair (provides huge surface area for absorption of H2O and nutrients from soil)
3. Root cortex
4. Xylem
5. Upward movement through xylem
6. Leaves
7. Diffusion through stomata
38
Roots take up water
- takes up water through osmosis (movement of water from a conc. of low solute (soil) to one of higher conc. of solute (cells)
- root hairs provide increased surface area for absorption of water and nutrients
- once water enters root, it can move in between cells (through apoplast) or through the cells themselves (through symplast)
- once it reaches layer of cells (endodermis), the water is re-directed to move up via the symplast - this allows for control of water uptake
- inside the endodermis is the Casparian strip which is how water movement is regulated (in and out)
39
Water movement
- once inside the xylem tracheids and vessel elements, water molecules adhere to each other by hydrogen bonding as well as to the walls of the xylem vessels
- this creates a column of water internally
- the water travels upwards to the leaves (the rate of travel can be 15m/hr in a large tree)
40
Water flow up the plant (tree)
- loss of water due to transpiration (movement of water out of leaf cells via the stomata) creates a "water deficit" or negative water potential inside the leaf
- this causes a "pull" of water into the leaf from xylem (because there is hydrogen bonding forming a column)
- this in turn pulls water up from the roots
- the "transpirational pull" is the main force that causes water to move up the plant, from roots to leaves
- IMPORTANT: stomata is important because it's where it's releasing water
- if trees didn't have stomata (which isn't possible) then the water would never move
- there wouldn't be a pull of water taking place inside the plant
41
Why do stomata stay open?
- to take up carbon dioxide and release oxygen during photosynthesis
42
Functions of stomata:
- would there be more stomata on the upper epidermis or the lower epidermis?
- stomata openin gand closing
- found in the epidermal layer of leaf cells
- more stomata on underside of leaves compared to upper surface as they aren't exposed to direct light and it's cooler
- guard cells of stomata regular the stomatal opening size --> the larger the opening, the more water will be lost
- stomata open when there's lots of water, when there's sunlight, and when potassium ion levels are high inside guard cells
- this causes water to flow in
- stomata close when there's not enough water, when it's dark, and when potassium levels are low
- this causes water to leave the guard cell
43
Role of potassium in stomatal opening and closing
- when potassium levels start to build up inside the guard cells, the stomata will open
- as K+ builds up it builds up salt/solute and that sucks the water in
- when potassium leaves the cell, it starts building up outside the guard cells
- as solute level is high, water gets taken out (via osmosis) and stomata opening closes
- mechanism of how plant knows K+ needs to go in and out of water is through signals that it gets from water deficit
- when plants aren't watered, it sends out distress signals that tell K+ to leave which causes H2O to leave and stomata to close
44
How do plants survive/adapt in desert climates?
ADAPTATIONS:
- plants have reduced leaf size and fleshing leaves to store water
- during dry seasons, plants can dry down but grow again when it rains
- some plants close the stomata during the day and open at night when it's cooler
- stomata may be located deeper inside the leaf than in the epidermis
- the leaves have thick waxy cuticles to retain water
- the plants have fewer stomata
- plants that live in the desert are called "xerophytes" (plants without H2O)
45
Function of the phloem
- during photosynthesis sugar is produced in the leaves that must be transported to other parts of the plant
- this requires movement from the source i.e. leaves, to where it is needed for growth i.e. sink
- sugar (sucrose) is "loaded" into the phloem cells by sucrose transporters
- this causes a high osmotic pressure which draws in water from the xylem
- this causes pressure to build up, which forces the flow of sugar down the plant
- the turgor pressure causes the sugar solution to move via "bulk flow" to reach cells that need it eg. growing fruit, shoots, roots, etc. ---> sugar is "unloaded" here
46
Process of phloem sugar loading and unloading
