Plant Structure and Function

1
Plant Structure and Function
of the 250,000 plant species on Earth, most of
our food comes from 0.1 of the species 2
main types of plants monocots and
dicots monocots one cotyledon dicots two
cotyledons
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Plant Structure and Function
monocots parallel leaf veins dicots branched
leaf veins monocots complex vascular
bundles dicots vascular bundles in a ring
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Plant Structure and Function
monocots flower parts come in 3's
dicots flower parts come in 4-5's
monocots fibrous root systems dicots
usually has a taproot
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Plant Structure and Function
just like animals, plants have specialized
tissues for different functions plants must get
nutrients from both the ground and the air root
tissue that absorbs water and minerals from the
soil also stores excess food and other
nutrients has a series of root hairs to
increase surface area for absorption
fibrous roots spread out broadly taproots go
down with small branches
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Plant Structure and Function
shoot system stems, leaves, and flowers of the
plants stems part of the plant that supports
the leaves and flowers node place where leaves
attach to stems internode areas of the stem
between leaves
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Plant Structure and Function
bud areas of new plant growth either
terminal (at the end of the stem- growing
longer) or axillary buds (at the sides of the
stem, growing out from the sides) apical
dominance terminal buds (apical) inhibit
axillary buds pruning makes plants bushier
because you remove the terminal buds, thus
allowing axillary buds to grow
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Plant Structure and Function
basic parts of plants can specialize just like in
animals carrots, beets, and turnips are all
modified roots strawberries, ginger and
potatoes are all modified shoots horizontal
stolons just below surface rhizomes,
tuber special storage
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Plant Structure and Function
petiole 'stem' of a leaf can be gigantic (ie.
celery) or miniscule (grasses) tendril
modified curled leaf or stem often used by
climbing plants
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Plant Structure and Function
plant bodies have only 3 tissue systems, arranged
differently in stems, leaves, and roots-- each
is continuous throughout the plant dermal
tissue outer covering-- protective cuticle
waxy covering over leaves (helps prevent
evaporation) bark hard outer covering of some
stems
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Plant Structure and Function
vascular system provides some support and mainly
long distance transport xylem (dead tubes of
cells) and phloem (living cells) that carry sap
xylem looks more hollow than the
phloem endodermis layer of cells surrounding
the vascular system only lets certain things
into the vascular system sap water carrying
sugars and nutrients from roots to the rest of
the plant
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Plant Structure and Function
ground tissue tissue not part of the dermis or
vascular systems fills in spaces between other
tissues pith ground tissue more central than
the vascular bundles cortex ground tissue
more toward the edges than the vascular bundles
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Plant Structure and Function
leaves are designed to increase the surface are
of the plant, absorbing light stomata pores to
let gasses into the leaves, protected by guard
cells mesophyll ground tissue of a leaf has
most of the photosynthesis vein vascular tissue
carrying water, nutrients, and sugars
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Plant Structure and Function
most plant tissues do not have a size limit,
unlike animals meristem growing tissue at
buds-- differs in roots and stems in roots,
dividing cells lie just behind a tough layer of
cells (root cap) cells specialize not long
after they are born
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Plant Structure and Function
lateral meristem tissue around the girth of the
stem that increase diameter made up of the
vascular cambium and the cork cambium vascular
cambium meristem tissue located between xylem
and phloem gives rise to secondary xylem and
secondary phloem that make up wood annual
growth makes growth rings of wood, some thicker,
some thin heartwood inner, denser
wood sapwood lighter, younger wood cork
cambium meristem tissue replacing cork layer
(part of the bark)
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Plant Structure and Function
plants have variable life cycles annuals plants
that develop and reproduce in one
year biennials plants that grow for one year
and reproduce in the next year perennials
plants that continue to grow year after year
after year some trees are thought to be
several thousand years old
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Flower Sex
flowers have 4 special modified leaves, called
floral organs sepals, petals, stamens, and
carpels
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Flower Sex
pollen is made in the stamens, and stored in the
anthers pollen grains land on the stigma, and
burrow down into the ovary flowers mature into
fruits/seeds fruits food for developing
embryos seeds embryo inside of a protective
covering, waiting to develop
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Flower Sex
seeds contain the early developing embryo until
it reaches a suitable site requires water to
germinate
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Many Plants Do Not Have to Have Sex to Reproduce
many plants can reproduce by cuttings
cuttings are from meristem tissue that can regrow
the whole plant plant cloning is easy-- take a
cutting and let it grow clone genetically
identical organism to a different individual
some clones develop naturally by sprouting from
roots, runners, etc true for some of both
monocots and dicots
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Many Plants Do Not Have to Have Sex to Reproduce
many commercial plants are grown from cuttings--
easier to control the characteristics of the
organisms problem if that clone is susceptible
to some disease, the entire crop can be
threatened monoculture large areas of land
from a single variety of plants 'GM' crop
genetically modified crop-- articifically
modified plant that has some desired
characteristic
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Plant Nutrition and Transport
plants get most of their 'food' from carbon
dioxide in the air bacteria in the roots of
many plants take nitrogen from the air into
nitrates that get absorbed by the
roots generally absorb only other elements and
water from the soil
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Plant Nutrition and Transport
water is pulled up through the xylem to the tops
of the plants transpiration force generated by
water removal/evaporation from the top of the
plant which pulls water all the way up the stem
or trunk controlled by guard cells at the
edges of the stomata
cohesion and adhesion properties of water that
hold it together
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Plant Nutrition and Transport
phloem transports sugars from their source
(leaves) to a sink (cell) plants must also
absorb essential nutrients from soil to the rest
of the plant 17 essential nutrients, 9 in
relatively large amounts ('macronutrients')
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Plant Nutrition and Transport
nutrient deficiencies often show up as phenotypes
in plants
lack of nitrogen stunted growth, yellow-green
leaves
boron deficiency
potassium deficiency yellowed leaves,
dead/brownish spots
phosphorus lack spindly and brittle growth
purple undersides of leaf
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Plant Nutrition and Transport
soil quality is one of the biggest limiting
factors for plant growth 3 layers of soil
topsoil must subject to erosion and weathering--
small rocks and humus humus remains of
partially decaying organic matter topsoil
also generally has various bacteria, fungi,
worms, etc 'B' layer less organic material,
more rock, clay, water less weathering 'C'
layer mostly broken down rock roots generally
grow in topsoil and B layer soils
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Plant Nutrition and Transport
soil erosion is a serious threat to
agriculture 'the Dustbowl' 1930's term for the
erosion of topsoil in the midwest threatened
many farmers with starvation by losing the best
soil
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Plant Nutrition and Transport
3 keys to reducing erosion 1)careful planting in
layers can reduce erosion 2)limited watering
prevents water erosion 3)organic fertilizer
release slower inorganic fertilizer runs off
quickly
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Plant Nutrition and Transport
organic farming strict set of guidelines
designed to protect the plants and the
environment from various potential contaminants
nutritional benefits have never been
observed goal is to protect the environment and
increase crop yields while protecting
biodiversity
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Plant Nutrition and Transport
'GM' plants have the potential to improve
nutrition dramatically some rice has been made
to make vitamin A, often deficient in
asians increased protein yields fight the most
common human malnutrition cotton plants have
been engineered to resist viruses
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Plant Nutrition and Transport
plants depend on fungi to help absorb nutrients,
bacteria to fix nitrogen
some plants are also parasites (mistletoe) or
carnivores (sundews, flytraps)