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Plant Structures
Chapter 31
Life Span
 Annuals – herbaceous (nonwoody)
plants that live 1 year only
 Biennials – take 2 years for life cycle
 Perennials – can be herbaceous or
woody but live longer than 2 years
 Deciduous – shed leaves before winter
 Evergreen – some leaves are always
present
Plant Tissues
 Three main tissue systems each of which
extends throughout the plant and consists
of 2 or more kinds of cells
 Ground tissue – photosynthesis, storage
and support
 Vascular tissue – conduction of water,
dissolved nutrients and sugars
 Dermal tissue – covering for plant body
 Tissue systems are further arranged into
organs: roots, stems, leaves, flowers
Ground Tissue
 Three cell types distinguished by their
cell wall structures
 Parenchyma – living, thin primary cell
walls; storage, secretion, photosynthesis
 Collenchyma – living, unevenly thickened
primary cell walls; elastic support
 Sclerenchyma – often dead at maturity,
thick secondary cell walls; support and
strength
Vascular Tissue
 Two complex tissues: xylem and phloem
 Xylem – conducts water and dissolved
nutrients
 Tracheids – conduct water; provide support
 Vessel elements – wider than tracheid; conduct
water; provide support
 Phloem – conducts food and provides
support
 Sieve tube elements – conduct dissolved sugar
 Companion cells – helps move sugar in and out
of phloem
Dermal Tissue
 Herbaceous plants – a single layer called
the epidermis
 Woody plants – continuous growth of new
tissues, covered by a layer of periderm
(bark)
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Epidermal cells - protection
Guard cells – open and close stomata
Trichome – hairy outgrowths; protection
Cork cells – reduces water loss; protection from
invading organisms
Plant Meristems
 Specific areas of the plant’s body where
growth occurs
 Cells in these areas divide by mitosis and
do not differentiate
 Plants can grow throughout their life span
 Two kinds of growth:
 Primary – increase in stem and root length
 Secondary – increase in girth
Apical meristems
 Primary growth occurs here
 Tips of roots and shoots
Lateral Meristems
 Secondary growth occurs here – only
in woody plants
 Vascular cambium – between the
wood and bark – adds cells to wood
and inner bark
 Cork cambium – located in the outer
bark and produce cork cells and
parenchyma cells