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BIOL 104 - Lecture 6
Plant tissues and tissue system
Terms in this set (38)
What does it mean when we talk about development? (3)
growth - irreversible increase in size, cell division and enlargement
morphogenesis - appearance of form (shape)
differentiation - cells become different from each other and functionally specialized
What is primary growth? What forms during this time?
- growth that occurs from the apical and axillary meristems. it extends the plant body length
- primary tissues form during this time
What are the different lives called in plants?
Annual < 1 year
Perennial > 1 year
Biennial < 2 years
What is secondary growth? What forms during this? What type of plant life is included in this?
- growth that occurs from lateral meristems, like vascular or cork cambium. This is the thickening of stems and roots
- forms wood and bark, and 2º vasculature
- all perennials
What are the three general cell types of the plant body?
Parenchyma, collenchyma, and sclerenchyma
What are the characteristics of parenchyma cells? Alive at maturity? Cell walls? Functions? Types?
- most numerous
- alive at maturity
- commonly only have 1º walls, but can have 2º
- maintain division potential
- functions: photosynthesis, storage, and secretion
What are the characteristics of collenchyma cells? Alive at maturity? Cell walls? Functions? Types?
- alive at maturity
- typically elongated
- unevenly thickened 1º walls
- rarely in roots
- typically supports growing stems, leaves and flowers
What are the characteristics of sclerenchyma cells? Alive at maturity? Cell walls? Functions? Types?
- present in 1º and 2º plant body
- often lack protoplasts at maturity
- thick, dignified, 2º cell walls
- functions: strength and supporting elements that have stopped elongating
- two types: fibers and sclerids
When are the first two apical meristems formed?
What do meristems contain?
Contains "initial cells" or "plant stem cells" that divide to produce the new cells over the plant's lifetime.
What are the three primary meristems?
protoderm, ground meristem, procambium
What are the primary tissues of the protoderm?
Epidermis (dermal tissue system)
What are the primary tissues of the ground meristem?
Ground tissues (parenchyma, collenchyma, and sclerenchyma) (ground tissue system)
What are the primary tissues of the procambium?
Primary xylem and primary phloem (vascular tissue system)
Order newest to oldest in shoot apical meristem: procambium, protoderm, apical meristem, ground meristem
protoderm, procambium, ground meristem, apical meristem
Order newest to oldest in root apical meristem: procambium, protoderm, apical meristem, ground meristem
protoderm, ground meristem, procabium, apical meristem of root
What do meristems have to balance? How do they do this?
Balance cell division with differentiation.
Cells at middle - maintain meristematic ID
Cell away from center - differentiate into organs/tissues
Meristems displaced apically (tip) - extending plant body length
How do cells get to the meristem periphery, if there is no cell movement?
Anticlincal divisions - perpendicular division
Periclinal divisions - paralle to surface division (lengthen)
Plant cells do not move relative to each otherm but are displaced from the center of meristems by oriented cell division.
Shaping of new tissues and organs requires what?
Requires oriented cell division and expansion
What is tropism?
Movement of plants toward or away from an external stimulus
What structure of the plant body is variable and which is precisely formed?
Global structures of the plant are variable, but local structures are precisely formed
- organs and tissues: invariant, determinate structures
- plant body: indeterminate structure
What are the 3 main tissue systems of the plant body?
Vascular: conducting (transport) tissues
Ground: internal, fundamental tissues
Dermal: outer, protective tissues
Where do these vascular tissues come from?
The procambium (vascular cambium) is the meristematic population for vascular cell types.
What determines the type of vascular cell formed?
The orientation of cell division
How do plants move materials around their bodies?
- conducts water and minerals
- functions in support
- roots to shoots
- conducts sugars = photosynthates
- conducts hormones, lipids, amino acids, micronutrients
- source to sink
What are the tracheary elements of xylem? What kind of plants are they in? How does water move in them?
- in all vascular plants
- water moves through pit pairs
- in angiosperms only
- water moves through perforated end walls and pit pairs
What are some key features of the xylem cell types?
- variable cell size, dies at maturity, elaborate secondary walls (annular, helical, scalariform, reticulate, pitted), perforation plates and pits
What is the last step of xylem development? How?
1) swollen primary wall at perforation site
2) disintegrating primary wall and degenerating nucleus
3) clear cell to have empty tube for H2O to flow
What are the principle conducting cells of phloem called? What are its 2 types?
- sieve cells (gymnosperms)
- sieve tube members (angiosperms): cells are alive at maturity but nuclei degenerate
What are companion cells? How do they connect?
serve to support function to sieve elements. Connects via plasmodesmata.
- deliver all information, molecules, proteins and ATP
- life support for sieve element
How does a sieve tube element and companion cell form?
Unequal division between 2 nuclei. Sieve tube element's nucleus degenerates. By widening plasmodesmata, it develops open pores to allow the photosynthates to pass through.
What types of cell make up the ground tissue system?
Simple and homogenous organization of: parenchyma, collenchyma, and sclerenchyma cell types
aerenchyma (aquatic and succulent plants): parenchyma with air spaces
What are the regions of ground tissue?
Cortex, pith, and mesophyll (in leaves)
What are the specialized cell functions of ground tissue?
Parenchyma cells retain ability to divide-- important for wound healing
support of growing stems, leaves, flower (collenchyma)
storage, transfer of compounds to/from vasculature secretory cells
What is the outermost layer of the plant body?
What comprises of the dermal tissue system?
- outer protective covering of the 1º plant body
- cuticle covers exterior
- outer protective covering in pants with 2º growth
What are some features of the dermal tissue?
- single layer of parenchyma cells
- regulates gaseous exchange between plant and environment
- outer cell walls coated with cutin + wax = cuticle (prevents water loss, reflects light, indigestible)
What are the specialized cell types in the epidermis?
Guard cells: pair of cells surrounding a stoma, open and close in response to turgor pressure
- root hairs: uptake water, nutrients, anchorage
- trichomes: reflect light, deter insects, hold humidity, and secrete material
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