Plant Growth and development Flashcards
What are plants composed of?
composed of cells, tissues and organs
tissue
is a group of cells, consisting of one or more cell types, that together perform a specialized function.
organ
consists of several types of tissues that together carry out particular functions
What are the 2 organ system?
Shoot system
Root system
Root system
below ground organs of the plant
All of a plant’s roots, which anchor it in the soil, absorb and transport minerals and water, and store food.
shoot system
(above ground organs of the plant)
The aerial portion of a plant body, consisting of stems, leaves, and (in angiosperms) flowers.
photosynthates
the sugars and other carbohydrates produced during photosynthesis, are imported from the shoot system.
What does the shoot system depend on? Root system?
are almost never photosynthetic; the sugars and other carbohydrates produced during photosynthesis, are imported from the shoot system
the shoot system depends on the water and minerals that roots absorb from the soil
What does the shoot system consist of?
stems
leaves
What do stems consist of?
Nodes
Internodes
Shoot apical meristem (SAM)/Apical buds
Axillary buds
What do leaves consist of?
Blades
Petioles
Veins -
Nodes
leaf attachment points
Internodes
stem between leaves
Shoot apical meristem (SAM)/Apical buds
grows up (aka terminal bud)
Axillary buds
can form lateral branches, thorns
Blades
flattened part of the leaf for photosynthesis
Petioles
joins the blade to the stem
Veins
vascular tissues
What does the root system consist of?
Taproots (eudicots)
Lateral roots
• Root hairs
Root apical meristem (RAM)
Taproots
(eudicots) -> main vertical root
energetically expensive to make, allows the plant to be taller, giving it access to more favourable light conditions and, in some cases, providing an advantage for pollen and seed dispersal
Lateral roots
sides roots
have root hairs
Root hairs
extensions of epidermal hairs for increased absorption
Root apical meristem (RAM)
increases root length
root
is an organ that anchors a vascular plant in the soil, absorbs minerals and water, and often stores carbohydrates and other reserves
primary root
originating in the embryo, is the first root (and the first organ) to emerge from a germinating seed
fibrous root system
a thick mat of slender roots spreading out below the soil surface
most monocots, the primary root dies early on and does not form a taproot.
prop roots
suport super tall trees
storage roots
store food and H20
pneumatophores
air roots on aquatic plants to obtain oxygen
green roots
photosynthetic roots in aerial plants
strangling aerial roots
anchor the plant in branches to the ground
Modified stems
horizontal stem- rhizomes
stolon- asexual runners
tubers- enlarged ends of rhizomes of stolons for food storage
modified leaves
spines- protection
storage leaves
reproduction leaves- cloning/ asexual reproduction
tendrils- climbing
stem
is an organ that raises and separates leaves, exposing them to sunlight
What are the types of tissue systems?
Dermal tissue system
Vascular tissue system
Ground tissue system (
Dermal tissue system
protective tissue layer
Epidermis
The dermal tissue system of nonwoody plants, usually consisting of a single layer of tightly packed cells.
Cuticle
waxy, protective layer on stems and leaves
Periderm
The protective coat that replaces the epidermis in woody plants during secondary growth, formed of the cork and cork cambium.
Guard cells
specialized epidermal cells for gas exchange
Trichomes
hairlike cells that reduce water loss, reflect excess light, defense
Vascular tissue system
transport tissue layer
What does the dermal system include?
Epidermis -> outermost cell layer
Cuticle -> waxy, protective layer on stems and leaves
Periderm->layer in woody plants that replaces the epidermis during secondary growth
Guard cells->gas exchange
Trichomes -> hairlike cells that reduce water loss, reflect excess light, defense
What are the different types of vascular system tissue?
Xylem -> water conducting tissue
Phloem -> transports photosynthates
Stele -> xylem + phloem
xylem
Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant.
phloem
Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.
stele
The vascular tissue of a stem or root.
xylem + phloem
Ground tissue system (
storage, support, and photosynthetic tissue layer)
What are the types of ground tissue?
Pith -> internal to vascular tissue
Cortex -> external to vascular tissue
pith
Ground tissue that is internal to the vascular tissue in a stem; in many monocot roots, parenchyma cells that form the central core of the vascular cylinder.
cortex
ground tissue that is between the vascular tissue and dermal tissue in a root or eudicot stem.
external to vascular tissue
Compare the stele in roots leaves and stems
in angiosperms, for , the root stele is a solid central vascular cylinder of xylem and phloem, whereas the stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem
Parenchyma cells
• Thin and flexible primary cell walls
• Lack secondary cell walls
• Large central vacuole
• Perform most of the metabolic functions of the plant
Can divide and differentiate to repair tissues
• Living cells
Chlorenchyma
photosynthetic parenchyma
Some contain amyloplasts, which store starch
Collenchyma cells
Grouped in strands, usually beneath the epidermis
Supportive function, flexible but not restrictive
Elongated cells with unevenly thickened primary cell walls
Living cells
Sclerenchyma cells
Contain secondary cell walls composed of lignin Functionally dead at maturity
Very rigid, structural support
What are the 2 types of Sclerenchyma cells?
function; support and strengthening
Sclerids -> irregular shaped (gritty texture in pears)
Fibres -> Long, slender strands, tapered (hemp fibres)
What are the 2 types of cells in xylem tissue?
Tracheids
Vessel Elements
Tracheids
Tubular, elongated cells with tapered ends
In the xylem of all vascular plants
Dead at maturity, thickened secondary cell walls of lignin
Water moves between cells via pits
Vessel Elements
Wider, shorter elongated cells with less tapering
Aligned end-to-end with perforation plates
In the xylem of angiosperms, a few gymnosperms, and a few seedless vascular plants
Dead at maturity, thickened secondary cell walls of lignin
pits
thinner parts where only primary cell wall is present in tracheids
What are the 2 types of phloem cells?
Sieve-tube elements
Companion cells
Sieve-tube elements
Alive, but lack a nucleus, ribosomes, cytoskeleton, vacuole
Long, narrow cells connected by sieve plates
Companion cells
Connected to the sieve-tube element
Non-conducting
Contains a nucleus and all organelles
Metabolic products are transferred from here to the sieve-tube element
What is the major difference between plants and animals?
Growth is not limited to juvenile or embryonic stages
Determinate growth
Some plant organs stop growing after a certain size
Similar to that of animals
leaves, thorns, and flowers
Indeterminate growth
Plants keep growing throughout their life due to meristems
ex- roots stems
meristem
Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth.
containing cells that can divide, producing new cells that elongate and differentiate
What are the 2 main meristems?
Apical meristems
Lateral meristems
apical meristem
Embryonic plant tissue in the tips of roots and buds of shoots
The dividing cells of an apical meristem enable the plant to grow in length( primary growth)
Lateral meristems
Enables secondary growth (increases girth, wideness)
A meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems
Vascular cambium
Adds secondary xylem and secondary phloem to the organ
Cork cambium
Replaces the epidermis with periderm in woody plants as it cracks and sloughs off
Explain the difference between woody and non woody plants in terms of primary growth?
in nonwoody the entire plant consists of primary growth, whereas in woody plants, only the nonwoody, more recently formed parts of the plant are primary growth.
root cap
protects the RAM from damage as the root elongates
What are the 3 zones of division in primary growth?
Zone of Division
Zone of Elongation
Zone of Differentiation
Zone of Division
Includes the stem cells/initials of the RAM
Produces new root cells, including cells in the root cap
Zone of Elongation
Most of the “growing” region of the root
Cell elongation pushes the root tip further down into the soil
3 tissue systems begin to develop
3 primary meristems become evident
Zone of Differentiation
Aka zone of maturation
• Cell differentiation into specific cell types
protoderm
is the outmost primary meristem that will give rise to the epidermis
ground meristem
Sandwiched between the protoderm and the procambium
gives rise to mature ground tissue.
What does the ground tissue of roots consist of?
consisting mostly of parenchyma cells, is found in the cortex, the region between the vascular tissue and epidermis.
endodermis,
Innermost layer of the cortex is the
, a cylinder 1 cell thick that is a selective barrier regulating movement of substances into the vascular stele
procambium
gives rise to the vascular cylinder (stele)
Pericycle
is the innermost layer of cells right inside of the endodermis
• Lateral roots arise from the pericycle
a solid core of xylem and phloem tissues surrounded by a cell layer
Compare the primary growth of roots in eudicots and monocots?
In most eudicot roots, the xylem has a star-like appearance in cross section, and the phloem occupies the indentations between the arms of the xylem “star”
- root with xylem and phloem in the centre
- vascular tissue in x shape
- less thick endodermis
- no pith
many monocot roots, the vascular tissue consists of a core of undifferentiated parenchyma cells surrounded by a ring of alternating xylem and phloem tissues
- root with parenchyma in centre
- vascular tissue in rings
- thick endodermis (suberized)
- pith present
What are the 3 primary meristems in root and shoots?
protoderm, ground meristem, and procambium
describe Primary growth in shoots
• The shoot is derived from the SAM, which is protected by the leaves of the apical bud
(Close together due to short internodes )
Shoot elongation is due to the lengthening of the internodes
SAM gives rise to the same primary meristems as the root
Branching arises from axillary buds (each with their own apical meristem)
• Plant hormones prevent buds close to the apical meristems from growing -> apical dominance
apical dominance
Tendency for growth to be concentrated at the tip of a plant shoot, because the apical bud partially inhibits axillary bud growth.
What is the stem covered by?
covered by an epidermis containing a cuticle
What tissues is ground tissue made up of?
mostly consists of parenchyma, with1-2 layers of collenchyma directly under the epidermis
• Sclerenchyma fibers may also be found to add additional structure and support
Describe the vascular tissue in stems
Vascular tissue runs from the root vascular cylinder all the way up the stem in continuous bundles
Compare the stems of monocots and eudicots
The vascular tissue of stems in most eudicot species consists of vascular bundles arranged in a ring
The xylem in each vascular bundle is adjacent to the pith, and the phloem in each bundle is adjacent to the cortex
In most monocot stems, the vascular bundles are scattered throughout the ground tissue rather than forming a ring
no pith
leaf primordia
Leaves develop from this
projections shaped like a cow’s horns that emerge along the sides of the shoot apical meristem
Protoderm in leaves
epidermis with a thick cuticle
stomata
allow exchange of CO2 and O2 between the surrounding air and the photosynthetic cells inside the leaf.
major avenues for evaporative water loss
surrounded by guard cells
.
mesophyll
• Ground meristem->gives rise to mesophyll(“middle leaf”)
Composed of specialized parenchyma cells called chlorenchyma
leaves specialized for photosynthesis
Do leaves exhibit secondary growth
NO
What are the 2 layers of mesophylls?
IN eudicots
Palisade mesophyll -> elongated parenchyma on the upper part of the lead
Spongy mesophyll -> loosely arranged parenchyma with large air spaces for movement of CO2/O2 gases
bundle sheath
composed of parenchyma cells surrounds veins
veins,
vascular bundles of the leaf) subdivide repeatedly and branch throughout the mesophyll.
Describe Secondary growth
increases the plants girth (diameter) through the activity of lateral meristems
Occurs in all Gymnosperms, most Eudicots and a select few Monocot species (coconut and palm trees)
Occurs in roots and shoots, never leaves
• occurs simultaneously with primary growth in woody plants
• Primary growth adds leaves, increases height
• Secondary growth increases girth in the older regions (adds Wooddy tissue)
Primary growth
Apical cells in the root/shoot tips are undifferentiated
When they divide, some daughter cells will remain in the meristematic region
Other daughter cells become partially differentiated into primary meristem cells (protoderm, ground, procambium)
Daughter cells from those will differentiate into cells in mature tissues
(direction of growth is top to bottom)
Compare the growth of the vascular cambium and cork cambium in terms of direction?
Vascular cambium has both direction growth cork has only one direction
Early wood
spring wood, xylem cells are large, with thin walls (amount of lignin is not that much)
Late wood
summer wood, xylem cells smaller, thicker cell walls (more lignin)
vascular rays
files of parenchyma cells(produced by vascular cambium) that connect secondary xylem and phloem and transports water between them, aids in wound repair(fill in gaps), and stores carbohydrates
Bark
is composed of all the tissues exterior to the vascular cambium (if young it could still consist of
Describe the process of secondary growth
1) Primary growth from the activity of the apical meristem is nearing completion and the vascular cambium has just formed
2) Although primary growth continues in the apical bud, only secondary growth occurs along the vascular cambium. The stem thickens as the vascular cambium forms secondary xylem to the inside and secondary phloem to the outside
3) Some of the initials of the vascular cambium give rise to vascular rays
4) As girth increases, secondary phloem can’t keep up with filling in the gaps. Eventually the epidermis ruptures and falls off. A cork cambium develops from the cortex parenchyma cells, producing cork cells
• Cork will replace the epidermis
5) In year 2 of secondary growth, the vascular cambium produces more secondary xylem and phloem. The cork cambium produces more cork cells
6) As girth increases, the outermost cork cells get sloughed off (just like the epidermis did)
7) If the cork cambium is lost during secondary growth, another one will form deeper in the cortex tissue to make more cork cells. If the cortex is eventually sloughed off, the cork cambium will arise from the secondary phloem tissue
8) Each cork cambium and the tissues is produces (cork) forms a layer of periderm (cork cell + cork cambium)
9) Bark is composed of all the tissues exterior to the vascular cambium (if young it could still consist of
Thick rings
warms years, good climate
Thin rings
less favourable climate
growth ring
can be seen between the previous year’s late wood and the new year’s early wood
Secondary xylem
towards inside of stem/root
Still composed of tracheids, vessel elements, fibres
Secondary phloem
towards outside of stem/root
• Still composed of sieve-tube elements and companion cells
Describe the role of the vascular cambium in secondary growth
responsible for the production of secondary vascular tissue
produces secondary xylem and secondary phloem
• Appears as a ring of meristematic cells
• Secondary xylem
• Secondary phloem
As these cells divide, they increase the circumference of the vascular cambium and also add secondary xylem to the inside of the cambium and secondary phloem to the outside. Each ring is larger than the previous ring, increasing the diameter of roots and stems
Lenticels
allow for gas exchange in the stems that have secondary growth
