Chapter 28
The plant body has a hierarchy of organs, tissues, and cells Plants, like multicellular animals: o Have organs composed of different tissues, which are in turn composed of cells
3 basic organs: o roots o stems o leaves Root System o root tip o root hairs
Functions: o anchor plants in soil o absorb minerals & water o store food
Found near the root tip Increase surface area Aid in the absorption of water and minerals
Shoot System o stems & leaves Stems o nodes internodes o buds terminal & apical axillary buds flower buds & flowers
Nodes o the point where the leaf is attached Internodes o the stem segments between nodes
Axillary buds o a structure that has the potential to form a lateral shoot (branch) Terminal buds o located near the shoot tip o causes elongation of a young shoot
Leaves o mesophyll tissue o flattened blade & stalk o petiole Veins o vascular bundles
Function o photosynthesis energy production CHO production o gas exchange o transpiration
Both systems depend on each other o roots depend on sugars produced by photosynthetic leaves o shoots depend on water & minerals absorbed by the soil from roots sugars water & minerals
Found in each plant organ 3 types: o dermal o vascular o ground
Epidermis o skin of plant o single layer of tightly packed cells covers & protects the plant
Carries out long-distance transport between roots & shoots 2 tissue types: o xylem o phloem
Moves water and minerals upwards from the roots Dead cells at functional maturity o only cell walls remain o need empty pipes to efficiently move H 2 O o transpirational pull
Basic unit of xylem A single elongated cell Aaaah Structure Function again!
Food-conducting cells Carry sugar & nutrients throughout the plant Sieve-tube elements & companion cells Living cells
Cell membrane, cytoplasm o control of diffusion Lose their nuclei, ribosomes, & vacuole o more room for transport of sucrose Cells o sieve tubes sieve plates end walls have pores to facilitate flow of fluid between cells o companion cells nucleated cells connected to the sieve tube help sieve tubes
Bulk of plant tissue Photosynthetic mesophyll Storage Support
Parenchyma Collenchyma Sclerenchyma Water-conducting cells of the xylem Sugar-conducting cells of the phloem
typical plant cells = least specialized photosynthetic cells storage cells tissue of leaves, stem, fruit, storage roots
Unevenly thickened primary walls Support o without restricting growth Alive at maturity the strings in celery stalks are collenchyma
Very thick, woody secondary walls Support (xylem vessels & tracheids) Rigid cells that can t elongate Dead at functional maturity Grittiness in pears, nutshells, seed coats
collect annual rings Dicot trees & shrubs Monocot grasses & lilies
A In seeds, two cotyledons (seed leaves of embryo) B Flower parts in fours or fives (or multiples of four or five) Leaf veins usually forming a netlike array Pollen grains with three pores or furrows Vascular bundles organized in a ring in ground tissue In seeds, one cotyledon (seed leaf of embryo) Flower parts in threes (or multiples of three) Leaf veins usually running parallel with one another Pollen grains with one pore or furrow Vascular bundles throughout ground tissue
phloem xylem
xylem phloem
Animals grow throughout the whole organism o many regions & tissues at different rates
Specific regions of growth Regenerate new cells
1 & 2 growth occur simultaneously but in different locations
Lengthens roots & shoots Produces the primary plant body o (parts produced by apical meristems) Primary growth in roots o covered by a root cap protection as root pushes through soil
Location: o tips of roots o buds of shoots Elongate roots & shoots through primary growth
shoot root
protecting the meristem
Apical bud & primary growth of shoot o region of stem growth protecting the meristem Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium Vascular tissue
Add thickness to woody stems o secondary growth
Woody plants grow in height from the tip o primary growth Woody plants grow in diameter from the sides o secondary growth makes 2 xylem and 2 phloem makes bark thickens & strengthens older parts of the tree rings around the tree
Aaaargh! Murderer! Arborcide! tree girdling What does girdling do to a tree?