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Characteristics of Living Things
- Organisation
- Energy
- Interaction with environment
- Reproduction
- Heredity
- Evolution
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Types of Tissue System
- Ground T.S.
- -parenchyma
- -sclerenchyma
- -collenchyma
- Dermal T.S.
- -epidermis
- -periderm
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Plant Cell
- -cell wall rich in cellulose
- -chloroplasts
- -vacuoles that digest waste
- -plasmodesmata connect adjacent cells
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Parenchyma Cells
- -thin cell walls
- -large vacuole
- -irregular shape
- -can have chloroplast
- -can store materials
- -Alive at maturity
- -Capable of cell division
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Parenchyma Tissue
- Occurs in:
- -cortex & pith of stem
- - leaf mesophyll
- - fruits/flowers
- - vascular tissue system
- Functions:
- -photosynthesis
- -storage
- -secretion
- -wound healing
- -has a role in water & sugar mvt.
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Sclerenchyma Cells
- -Generally dead at maturity
- -Cell wall
- -very thick
- -secondary cell wall thickened with ligin and cellulose
- -Types of sclerenchyma cells
- -fibers
- -sclereids
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Sclerenchyma Tissue
- Occurs:
- -vascular tissue
- -areas where support is need
- Function:
- -support
- -strength
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Collenchyma Cells
- -Alive at maturity
- -Cell walls
- -unevenly thickened
- -stretch and elongate
- -Elongate, prism shape
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Collenchyma Tissue
- Occurs in:
- -young, growing organs
- -below stem epidermis
- -stalk of leaf
- Function:
- -support without rigidity
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Water Conducting Cells of the Xylem
- -2 types: tracheids and vessel elements
- -elongate cells
- -cell walls have puts and lignin
- -cells are dead when functioned
- -A pit is an area missing a secondary cell wall; allows for water transfer across cells.
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Tracheids
- -lack perforations
- -"safer" method of water transport
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Vessel Elements
- -have pits
- -have perforations in cell wall
- -more efficient conductions of water than tracheids.
- -found in angiosperms.
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Other Cells of the Xylem
- -parenchyma cells for storage
- -fibers for support and storage
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Phoelm
- Comprised primarily of sieve-tube elements, which conduct nutrients through the plant.
- Contains sclerids for support
- Contains fibers for support
- Contains parenchyma cells for storage
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Sieve-tube Elements
- found in angiosperms
- elongate cells
- alive at maturity
- contain sieve plates
- has a companion cell; the companion cell has a nucleus whereas the sieve-tube elements don't. It directs the sieve-tube's metabolism.
- Contains a proteinaceous substance called P-protein
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Dermal Tissue
Comprised of the epidermis and the periderm (in woody plants).
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Epidermis
- comprised of guard cells, stomata, trichomes, root hairs, specilized cells, and unspecialized cells.
- A waxy cuticle prevents water loss
- typically lacks choloroplasts
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Stomata
- plural of stoma or stomate
- an opening in the leaf controlled by guard cells
- as the guard cells fill with water, it opens.
- the guard cells regulate gas exchange
- generally found on leaves
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Trichomes
- Generally found on stems and leaves
- One purpose is for defense; the trichomes could be toxic, contain silica crystals that cut, etc.
- Increases surface area
- Helps prevent water loss; hairs cover stomata
- Can help keep the plant cool
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Root Hairs
Small extensions of the epidermis that increase the surface area of the roots
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Periderm
- replaces epidermis in stems/roots with secondary growth in woody plants
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3 Steps of Plant Growth
- cell division
- cell elongation
- cell differentiation
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What is a Meristem?
- meristematic tissues = clumps of cells with dense cytoplasm and proportionately large nuclei
- areas of active cell division
- Responsible for both primary and secondary growth.
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Apical Meristems
- primary growth
- located at tips of all roots and stems
- indeterminate growth
- two types: root apical meristem and shoot apical meristems
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Primary Meristems
- responsible for primary growth
- come from apical meristems
- partly differentiated tissues that remain meristematic (in other words, can still go through mitosis)
- initiated during embryonic development
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Lateral Meristems
- results in secondary growth
- Two types:
- vascular cambium --> Secondary xylem and phloem
- cork cambium --> periderm
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