Kingdom Plantae like Animalia is a group of multicellular eukaryotic

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Kingdom Plantae like Animalia is a group of
multicellular eukaryotic organisms.
 Plants face many of the same problems we have talked
about for animals.
 Plants must acquire energy and exchange matter; plants
capture solar energy directly
 Both plants and animals face similar challenges to living
on land
Plant Structure and GrowthPlant bodies are simple
 only a few types of basic organs
 roots with root hairs
 stems
 leaves
 flowers + fruit
 fewer cell types and tissue types than animals-names not
stressed
 all cells begin as parenchyma and differentiate into other
types:
 photosynthetic leaf cells (Fig 35.19a b)
 phloem for transporting sugars
 some cells become functional only when dead: xylem
and fibers (note economic importance of these cell
types)
 leaves modified in many different ways (fig 35.6)
 for photosynthesis from sunny deserts to rainforest shade
 as spines in cactus
 tendrils in peas
 as colorful signals to animals
Plant bodies are potentially immortal
 plants are rooted in place, but their growing tips
continually explore new territory
 some shoots grow vertically and some grow horizontally
 meristems are sites of plant growth-sites of rapid cell
division
 only two types of meristems in plants (fig 35.12):
 apical meristems at ends of growing shoots-buds (fig
35.17)
 primary growth—increases in length
 generate plant form, i.e., leaf arrangement, lateral
meristems
 vascular cambium in a cylinder within the stems of
woody plants (fig 35.23)
 secondary growth—increases in diameter in woody
plants
 increase diameter through accumulation of xylem or
wood
 cambium cells are a meristem-zone of rapid cell
division
 cells to the inside differentiate into xylem
 cells in the outside differentiate into phloem
 cuticle and epidermis break up and are replaced by
cork cambium
 growth of plants and animals different
 modular vs unitary
 continually add young modules at growing tips
 trees that are rooted in one place eventually get old
and die
 plants that produce horizontal stems can live 1000’s of
yrs, and continually move around
 do plants perceive where they are?
 receptors to light intensity and quality (pigments)
 receptors for touch (?)
 receptors for gravity (statoliths-starch grains settle to
bottom of cells in roots)
 do they respond to different conditions?
 variety of hormones stimulated by different receptors
that change growth
 ex. pigments receive information on light
environment; shade will stimulate longer spacers
between leaves, light will stimulate leaves
 ex. wind or touch stimulates plants to grow shorter,
stouter bodies with more fibers and support in the
stem
 ex. roots can rapidly reorient their grow to
gravitational pull
Vascular tissues are critical adaptations for
terrestrial plants
 As plants increase in size their surface area to volume
increases
 As plants move onto land, the moist cells inside the body
must be protected from drying out
 Plants evolve to do two things to solve this problem:
o Produce a waxy cuticle on the surface of their
epidermis that prevents water loss
o Produce stomates to control entry and exit of gases
o Circulate fluid and matter through their body in
specialized vascular tissues
The most primitive plants lack a vascular system
 Mosses (Phylum Bryophyta) lack waxy cuticle and
vascular system
 What are the consequences of no waxy cuticle and no
vascular system?
o Must live in moist locations
o Must remain small
More advanced plants have waxy cuticle and
vascular tissue
 Phyla: Pteridophyta (Ferns), Gymnosperms (conifers)
and Angiosperms (flowering plants)
TRANSPORT IN PLANTS
First need to list what plants need transported in
terms of energy and matter
(fig 36.1):
 Energy: harvested directly from solar radiation by cells
containing chloroplasts (Fig 35.19a,35-19b-Stomata.jpg,
c)
o Energy is transported through body in the form of
sugars
 Matter:
o water is used in photosynthesis and lost from
stomates
o carbon dioxide is used in photosynthesis and
brought in thru stomates
o oxygen is used in mitochondria and is brought in
thru stomates
o carbon dioxide is lost from mitochondria and exits
thru stomates or is reused in photosynthesis
o oxygen is a by product of photosynthesis and is lost
thru stomates
Water + dissolved nutrients move in xylem

rootsshoots in xylem
 driving force is loss of water thru stomates--
transpiration
 99% of water in roots is lost thru stomates
 CO2 gain is linked to H2O loss
 what causes stomates to open?
 light
 low CO2
 what causes stomates to close
 loss of turgor or water pressure
 cohesion-tension mechanism (transpiration movie)
 water loss from cells in leaves to intercelluar space then
thru stomates
 provides negative pressure and pulls water out of xylem
to replace water lost from leaf.
 negative pressure gradient is maintained all the way to
roots
 properties of water important
 cohesive due to hydrogen bonds
 adhesive to sides of xylem elements
 evidence to support
 1. xylem sap recedes from cut surface of stem-cut stems
will wilt due just as siphon will stop if you get an air
bubble in them
 2. Stems shrink when transpiration is great
 3. Water starts moving first in leaves in morning
 factors affecting transpiration
 humidity
 wind
 temperature
 light
Sugars move from sources to sinks in phloem
 sieve tubes run in bundles adjacent to xylem (fig 36.17)
 sources are sites where sugars are actively loaded into
sieve tubes, i.e., photosynthetic leaves or storage
 sinks are sites where sugars are pulled out of sieve tubes
and used, ie., growing tissues, storage organs, fruits,
parasites
 phloem connects sinks and sources
 turgor pressure builds up at sources
 turgor pressure is reduced at sinks
 results in bulk flow
 resources can move in one direction one day, and
reverse the next in phloem
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