Plants structure and Function Flashcards
what is unusual about plant cells
Plant cells are unusual as the live in boxes, making up the cell wall. This means that plant cells can’t move. This is helpful in a few ways, including preventing tumours from becoming cancerous.
describe the evolution of the kingdom of plants and bryophytes
470 mya plants originated, having evolved from Ancestral green alga. At this time Liverworts split off from the rest of plants. Soon after, Mosses, and then Hornworts split off. Liverworts, Mosses, and Hornworts are all grouped into Bryophytes, despite not being a monophyletic group.
describe the evolution of vascular plants
425 mya vascular plants evolved, and Lycophytes (Club mosses, spikemosses, quillworts) split off from other plants. Then Monilophytes (ferns, horsetails, whisk ferns) split off. Lycophytes and Monilophytes are both Seedless vascular plants.
describe the evolution of seed plants
360 mya seed plants originated, and Gymnosperms and Angiosperms diverged. Seed plants
Majority of plants, 290,000, are angiosperms.
describe monocots
Monocots have one cotyledon in their seeds, veins usually run parallel in the leaves, vascular bundles are in a complex arrangement in stems, floral parts are usually in multiples of three in the flowers, and the roots are in a fibrous root system.
describe Eudicots
Eudicots have two cotyledon in their seeds, veins are usually branched in the leaves, vascular bundles are arranged in rings in the stems, floral parts are usually in multiples of four or five in the flowers, and taproots are usually present.
what are simple tissues
Simple tissues are made up of only one cell type
Complex tissues are made up of more than one cell type
Three types of simple tissues:
- Parenchyma
- Collenchyma
- Sclerenchyma
describe Parenchyma
Composed only of Parenchyma cells
- very common in plants
- alive at maturity
- Surrounded by a thin and flexible primary cell wall (cellulose only)
- Shape: Isodiametric
describe the functions of parenchyma
- most of metabolic functions of a plant: photosynthesis, storage, seed dispersal, wound repair.
- Specialized functions: Aeration of roots in water → aerenchyma
- In flooded areas plant roots can get oxygen by making Air tubes called aerenchyma from parenchyma and programmed cell death.
describe Collenchyma
Composed only of collenchyma cells
- common only in a few plant families
- Alive at maturity
- unevenly thickened primary cell walls
- Shape: longer than wide (elongated)
- Flexible and elastic
- Functions: flexible support without restraining growth
- have thick primary cell wall
describe Sclerenchyma
Thin primary cell wall and a very rigid secondary cell wall with lignin
- Inflexible and inelastic, dead at maturity
- two types: fibres and sclereids
describe Sclereids
Sclereids:
- Stone cells in pears (gritty texture)
- Hardness of nutshells and seed coats: pass digestive tract unharmed
- defence against predators
how do we use fibers
Human uses of Fibers
- Cells are 1-10 cm in length, usually grouped in strands
- Found in all plant organs
- Commercial uses: rope (hemp), clothing (ramie), linen (flax), MDF boards (wood fibres), bioplastic composites (hemp, flax, …)
how do we use Sclereids
Human uses of Sclereids
- walnut shell abrasives: clean surfaces without damaging underlying material can absorb contaminants. Renewable and environmentally friendly
- Cosmetics: walnut shell exfoliator, skin-smoothing.
what are the different cell walls made of in plants
- Primary cell wall:
- Carbohydrates: cellulose, hemicellulose pectin
- Proteins
- Secondary cell wall:
- as above, but more structured
- Lignin
- Phenolic polymer
- Polymerized around cellulose fibrils
- Provides stiffness and mechanical strength
what are the two types of complex tissues
Two types of complex tissues:
- Xylem
- Phloem
What are Xylem
- Composed of living cells and dead cells
- Parenchyma (alive):
- active solute transport into the xylem, defense
- Sclerenchyma (dead):
- structural support
- Tracheary elements (two types, both dead)
- Tracheids
- Vessel elements
- Water/mineral transport from roots to leaves (passive)
Wood is a type of xylem
describe the Tracheary Elements in Xylem
Tracheary Elements in Xylem
Dead at maturity, develop, produce the secondary cell wall, die, leave empty tubes
Perform water transport
Tracheids: all vascular plants, dead at maturity
- Long, thin cells with tapered ends, water moves through pits
Vessel elements most angiosperms
- wider, shorter thinner walled,
- aligned end to end to form micro-pipes
Tracheary Elements have secondary cell walls in rings or spirals around the primary cell walls that are heavily lignified. These perform the same function as the spiral thickenings of vacuum hoses: provides support and keeps the tube open.
what do Parenchyma cells do in Xylem
Parenchyma Cells In Xylem
- Only living cells in Xylem
- Unloading of minerals from vessels and tracheids
- Active transport of solutes including hormone
- e.g. the hormone auxin, which controls development (inhibits branching). A tree with less auxin has more branches (”Broccoli tree”)
what do Sclerenchyma cells do in Xylem
Sclerenchyma Cells in Xylem
- Sclerenchyma (structural support): fibers (and sclereids)
what are the functions each part of xylem
Functions:
- Tracheary elements:
- transports water upwards (passive)
- transports some dissolved minerals upwards (passive) - Xylem Parenchyma:
- transport plant solutes such as the hormone auxin (active downward transport)
- Defence, wound healing, can store carbohydrates - Xylem sclerenchyma:
- structural support
what are Phloem
- Composed of living cells and dead cells
- Sclerenchyma cells (dead):
- support
- Parenchyma cells (alive):
- Albuminous/companion cells
- Loading/unloading of sugars
- defence
- Sieve elements (alive[ish])
- transport of organic compounds and hormones
what are Sieve elements in phloem
Sieve elements
- Sieve-tube elements (angiosperms), connected via sieve plates
- alive but missing nucleus and ribosomes. “the living dead”
- Sieve cells (gymnosperms)
what are Parenchyma cells in phloem
Parenchyma
- sieve-tube elements paired with companion cell (only in angiosperms)
- Sieve cells paired with albuminous cells (gymnosperms)
- (Un)loading of organic compounds and some minerals
- Provide resources needed by sieve tubes
what are the functions of each part of phloem
Functions
- Sieve elements:
- transport organic compounds upwards and downwards (passive)
- transport of plant hormones(e.g. cytokinins regulating cell division)
- Phloem parenchyma:
- (un)loading of compounds (active)
- Supporting sieve elements
- Sclerenchyma
- Structural stability
- defence (prevents insects and microbes from getting into the sugar rich zone of the phloem)
what are the main tissue systems in plants
Dermal tissue:
always on the outside (epidermis, periderm/bark)
Vascular tissue (Xylem and phloem)
leaf: network of veins
Stem: vascular bundles
Root: vascular cylinder in the middle
Ground tissue
leaf: mesophyll: palisade and spongy tissue
Stem: cortex and pith
Root: cortex and pith (not all roots have a pith)
what are the four plant organs and two organ systems
A group of tissue systems that perform specific functions
Four plant organs:
- Roots
- Stems
- Leaves
- reproductive organs
Two organ systems:
- Shoot system
- Root system
how do roots and stems grow
- Root and stems have indeterminate growth
- Leaves have determinate growth
Roots and shoots have apical meristem that lead to primary growth
Root apical meristems and Shoot apical meristem
These are the points of growth and the end of a root or shoot
what do roots do
Basic functions include Anchorage, uptake of water and nutrients
Root systems:
Monocots have a fibrous root system
Dicots have a taproot system
what do young roots have
Very young roots have a central stalk with root hairs that branch off as an extension of a single cell. The root hairs give more surface area and allow water and nutrient intake. Also help anchor plant.
what do green roots do
Green roots: some orchids or other plants can germinate on the bark or branches of other trees and can produce roots which anchor it to the host tree. They also produce green roots which can photosynthesize. Some can’t even produce proper shoots or leaves, just roots.
what do strangling aerial roots do
Strangling aerial roots: Certain plant seeds will germinate on top of an existing tree to get a height advantage. Then its roots grow down and around the pre-existing tree, killing it and using it as anchoring.
what do Pneumatophores do
Pneumatophores: These are from trees that live in mangrove systems. They grow down into the ground, then back up into the air to provide oxygen to the roots since those are in anoxic mud.
what do Prop roots do
Prop roots: Mechanically support a long tall stalk, but “propping” it up.
what do storage roots do
Storage roots: things like beets store food and water in their roots.
what are the 4 difference parts of a root tip
- Zone of differentation
- Root hairs
- vascular tissues
- Zone of elongation
- cell elongation
- initial differentiation
- dermal, ground, vascular
- Apical meristem
- Cell division (growth)
- Root cap
- Protection and soil lubrication (allowing growth)
What is the organ system shoot
Shoots include stems and leaves
What is the stem
the main central stalk of the plant
what are vegetative and reproductive shoots
Both branch off laterally from the stem and can lead to leaves (vegetative) or reproductive structures like flowers (reproductive)
What are the two parts of a leaf
Leaves are made from a blade (leaf bit) and petiole (supporting stalk)
What are nodes and internodes
Nodes are points of attachment or branching for leaves, buds, and flowers
Internodes are the spaces between nodes on the stem
Where does primary growth occur on the shoots
From an apical meristem at the top of the shoot
What happens to cells below the meristem of a shoot
They get older the further they are from the meristem, and they differentiate into dermal, ground, and vascular cells
What are Leaf Primordia
Structures that develop right below the meristem and grow upwards above it, later becoming leaves. Help protect the meristem.
How are Edicots organized in the stem in regards to primary growth
They have a ring of vascular bundles outside of the pith and inside the epidermis. Ground tissues connect the pith to the cortex (which is inside the epidermis) Can grow wider
How are Monocots organized in the stem in regards to primary growth
Monocots have complex arrangements of vascular bundles scattered around inside the epidermis.
What are Rhizomes
Rhizomes: The base of plants like iris which are a horizontal shoot just below the surface. Vertical shoots emerge from auxiliary buds on the rhizome.
What are Bulbs
Bulbs: Vertical underground shoots consisting mostly of the enlarged bases of leaves that store food. You can see the layers of modified leaves.
What are Tubers
Tubers: like potatoes are modified stems used for storage
What are Stolons
Stolons: like in strawberries run along the grounds and are used for vegetative propagation.
what are axillary buds
Axillary buds are at the base of the petiole and contribute to plant growth and reproduction by developing into branches.
What is the difference between simple and compound leaves
Simple leaves have a single, undivided blade. Some are deeply lobed. Axillary bud at base.
Compound leaves have a blade consisting of multiple leaflets. A leaflet has no axillary bud at its base.
What is the skin of a leaf called
The “Skin” of a leaf is called the cuticle. It has openings called stoma which are surrounded by guard cells.
The Cuticle prevents water from evaporating and microorganisms from reaching the rest of the leaf.
What are stoma
Stoma allow gas exchange. Can be open or closed. More stoma are present on lower side of leaf.
What is underneath the upper epidermis in leaves
Below the upper epidermis is the Palisade mesophyll where most photosynthesis occurs.
What is below the Palisade mesophyll in leaves
Below the palisade mesophyll is the spongy mesophyll. Veins (Xylem, Phloem, enclosed in bundle-sheath cells) pass through the spongy mesophyll.
There are also fibres throughout the mesophyll, which give stability.
What make up dermal, ground, and vascular cells in leaves
Cuticle + guard cells + epidermal cells = Dermal cells
Palisade + Spongy mesophyll + bundle sheath cells = Ground cells
Xylem + Phloem = Vascular cells
What are four examples of modified leaves
Bulbs have leaves for storage, make layers.
Spines in cacti are leaves for defence (Photosynthesis in stem)
Plants like pea plants have tendrals for climbing + stability (which are leaves)
Mother of a thousand use leaves for reproduction, they drop off and can grow into plants.
