Unit 1 Intenal Organization of the Plant Body Flashcards
Meristems
Embryonic tissues
-Regions or populations of cells that can divide
-A continuing source of new cells
Ex: Stem cells
What are the two parts of the meristem?
Apical meristem
Primary meristem
Apical Meristem
Give rise to roots, stems, leaves and flowers of the adult plant
- Found in shoot and root tip
- Are composed of initials (cells that perputate the meristem–they maintain the meristem as a continuing source of new cells)
Primary Meristem
Partly differentiated tissues that remain meristematic for some time
- Include the protoderm, procambium and ground tissues
- The unlimited/prolonged activity of the apical meristem means that plants have indeterminate growth
What are the four characteristic parts of the meristem?
1) Development
2) Growth
3) Morphogenesis
4) Differentiation
Development
Instructions in the DNA cause the process (the events that form an organisms’ body)
-The specific pathway is determined by the environment in plants
Growth
Is an irreversible increase in plant size
-Caused by cell division and cell enlargement (most by this type of growth)
Morphogenesis
Is the process by which a plant assumes a particular shape or form
-Accounts for morphology of different species
Differentiation
Is how cells with identical genetic makeup become different from one another
-Controlled by gene expression and position in the developing organ
Ex: from a meristemic cell can become a vessel, sieve tube, fiber, or parenchyma
What produces the tissues?
Apical meristems produce primary meristems that produces tissues
What makes up the primary meristem?
1) Protoderm
2) Ground
3) Procambium
What tissue system makes up the protoderm?
Epidermis (dermal tissue system)
What tissue system makes up the ground?
Ground tissue system
-produces fibers (rigid cell wall make enzymes) and collenchyma cells (function in support)
What tissue system makes up the procambium?
Vascular tissue system
What makes up a simple tissue?
Made of one type of cell
-ground tissue
What makes up a complex tissue?
Made of two or more types of cells
-dermal and vascular tissue
What is primary growth of the plant?
- Is growth in length (height)
- Produced by apical meristems in root tip and shoot tip
What is secondary growth of the plant?
- Growth in diameter
- Produced by lateral meristems
Cork cambium
Produces the periderm or outer layer (part of the “bark”)
-secondary growth
Vascular cambium
Produces secondary xylem (“wood”) and secondary phloem (“bark”)
-secondary growth
Dermal Tissue
Outermost cell layer of the primary plant body
- This is the leaves, floral parts, fruits and seeds
- Outermost layer of roots and stems (part of this system) until they have secondary growth
What makes up the dermal tissue?
- Epidermis (or periderm in woody plants)
- Cuticle
- Lacks chloroplasts
What is the function of the epidermis?
- Functions in protection (mechanical)
- Aerates the internal issues through the stomata
- Is covered by a cuticle (a layer of wax-cutin and lips that covers the above ground portion of all land plants), extra protection and reduces water loss
What are the specialized dermal cells?
1) Guard Cells
2) Trichomes
3) Root hairs (increase surface layer)
4) Leaf hairs (single cell-layer thick)
(2-4, functions in protection)
What are guard cells?
-Contains chloroplasts
-2 of them form the stomata
-found at the bottom of the lower layer epidermis
-openings on the surface of leaves through which water evaporates and CO2 is absorbed
(when filled which H2O they open and release–> then they collapse, mechanical barrier/door)
What makes up ground tissue?
Called the pith (inside the vascular tissue) and cortex (outside the vascular tissue) in stems and roots
What cells make up the ground tissue system?
1) Chlorenchyma
2) Parenchyma
3) Collenchyma
4) Sclerenchyma
Chlorenchyma
Parenchyma cells that contain chloroplasts
What is the passageway of the 3 ground tissue cell types in a cell?
Collenchyma–>Sclerenchyma–>Parenchyma
Parenchyma
Cells occur in continuous masses in the mesophyll of leaves, the cortex and pith of stems and in the flesh of fruits
-cells are living at maturity
What is the function of the parenchyma?
Involved in photosynthesis, storage and secretion
-metabolic process (respiration)
conduction, wound healing and regeneration
Collenchyma
Cells are living at maturity; tissue supports young, growing organs
- Occurs in discrete strands or as cylinders beneath the epidermis in stems and petioles
- Cells are elongated
What is the function of the collenchyma?
Supporting tissue of growing stems, leaves, and floral parts
Sclerenchyma
Strengthen and support plant parts that are no longer growing
- cells have thick lignified secondary walls
- includes fibers and sclereids
What is the function of fibers (sclerenchyma)?
Support (mature parts), storage
What is the function of sclereid (sclerenchyma)?
Mechanical, protective
Sclereids (sclerenchyma)
Short cells, often branched
- makes up the seed coats, shells of nuts and stone cells of stone fruits (pear)
- Cells can be living or dead at maturity
What makes up the vascular tissue?
Xylem and Pholem
What cells make up the xylem?
Tracheid and Vessel Element
What cells make up the phloem?
Sieve cel, Albuminous cell, Sieve-tube element, Companion Cell
What is the xylem?
Includes vessels and tracheids (conducts water and minerals)
- parenchyma (storage)
- fiber cells (support)
What are water-conducting cells?
These are tracheids and vessel elements
- Vessel elements (perforations on the end walls or the end walls dissolve completely)
- Elongated cells with secondary walls that lack protoplasts at maturity
- May have pits in their walls
- Found in gnetophytes and angiosperms
2 types of xylem development
1) Protoxylem
2) metaxylem
Protoxylem
First part of the xylem system
- Cells are smaller in diameter
- Secondary walls (have rings or spiral thickenings); makes it possible to stretch or extend the cell as it elongates (narrow in diameter)
Metaxylem
Differentiates after the protoxylem; after the plant part
-cells are rigid and cannot be stretched (wider in diameter)
Tracheid
- Xylem
- elongated and tapering
- contains pits but no perforations
- dead when functional
- water-conducting cell in mostly gymnosperms, a few seedless vascular plants and some in angiosperms
Vessel Element
- Xylem
- elongated (shorter than a tracheid)
- contains pits and perforations
- dead when functional
- water-conducting cell in angiosperms
What is the phloem?
Includes sieve-tube elements with companion cells (long-distance transport), sclerenchyma (support), and parenchyma (storage)
-Is principal food conducting tissue in the plant (transports sugars, amino acids, lipids, hormones, micronutrients, proteins and RNA)
Sieve Plates
Slime plug may result during sectioning of sieve-tube element
Sieve Cell
- Pholem
- elongated and tapering
- living at maturity
- food-conducting element in gymnosperms
Albuminous Cell
- Pholem
- elongated and living at maturity
- Plays a role in the delivery of substances to the sieve cell (informational molecules and ATP)
Sieve-tube Element
- Pholem
- elongated and living at maturity
- Food-conducting element in angiosperms
Companion Cell
- Pholem
- generally elongated and living at maturity
- Plays a role in the delivery of substances to the sieve-tube element (informational molecules and ATP)
