Transcript Topic 9 Plant Biology

Plant Biology
Konrad Pawlikowski
Transport in the Xylem
of Plants
Transpiration is the inevitable
consequence of gas exchange in the leaf.
• Transporation is the loss of water from plants through
the stomata in the leaves.
• Guard cells help adjust the stoma and allow them to
release the water.
• Exchange of gases sustains photosynthesis.
Plants transport water from the roots to the
leaves to replace losses from transpiration.
• When water evaporates new water comes through the roots.
• Goes through Xylem.
• This is because of cohesion.
The cohesive property of water and the
structure of the xylem vessels allow transport
under tension.
• Xylem is a tube made of cellulose.
• This provides a sturdy structure for transport of minerals and
water.
The adhesive property of water and
evaporation generate tension forces in the
leaf cell walls.
• Water is pulled out of the plant into the leaf.
• Light and temperature turns water into the vapour state.
• Water exits through the stomata.
Active uptake of mineral ions in the roots
causes absorption of water by osmosis.
• Passive transport.
• Water from soil flows from high to low concentration.
• Ions go through active transport.
• Protein Pumps.
Adaptations of plants in deserts and in
saline soils for water conservation.
• Plants adapt to water loss in harsh conditions.
• Waxy Leaves.
• Firs and Pines.
• Succulent.
Drawing the strucutre of primary xylem
vessels in sections of stems based on
microscope images.
Transport in the Phloem of
Plants
Plants transport organic compounds from
sources to sinks.
• Translocation, organic compounds
are carried in Phloem tube.
Incompressibility of water allows transport
along hydrostatic pressure gradients.
• Hydrostatic pressure helps move water.
• Water moves from high to low concentration from xylem to
phloem, through osmosis.
• This water movement occurs when there is different water
potential.
Active transport is used to load organic
compounds into phloem sieve tubes at the
source.
• Sieve tubes are specialized cells that make up the phloem.
• These cells are lvining and contain mitochondria used for ATP
production.
High concentrations of solutes in the phloem
at the source lead to water uptake by
osmosis.
Raised by hydrostatic pressure causes the
contents of the phloem to flow toward sinks.
• The translocation theory.
• Movement of minerals from source to sink.
• Water is recycled in the end.
Structure function relationships of phloem
sieve tubes.
Microscope images.
• Notice the sieve tubes are separated.
Growth in Plants.
Undifferentiated cells in the meristems of
plants allow for indeterminate growth.
• Plants grow only in meristems.
• These tissues are made of cells that undergo cell division.
Mitosis and cell division in the shoot apex
provide cells needed for the extension of the
stem, and development of leaves.
• Small cells therefore fast cycles which mean fast growth.
Plant hormones control growth in the
shoot apex.
• Auxin- root growth.
• Gibberellin- cell division, flowering, size.
• Cytokinin- cell division, aging of leaves.
• Absisic acid- Stress hormone, reduces growht during times of
stress.
Plant shoots response to enviromental
tropisms.
• Tropisms are external factors that influence plant growth.
• Phototropism.
• Gravitropism.
Auxin
• Major role in the growht of plants.
• Auxin Efflux pump.
• Auxin changes gene expression patterns.
Reproduction in plants.
Flowering Involves a change in gene
expression in the shoot apex.
• mRNA moves from leaf to flower
meristem.
• Differentiation of meristem into the
flower happens due to the construction
of protein.
The switch to flowering is a response to the
length of light and dark periods in many
plants.
• Long and Short day plants.
• Each grow in different periods.
• Each grow depending on the enviroment they are at.
• Use Phytochromes which are pigments which measure length
of light.
Success in plant production depends on
many factors.
• Polination
• Fertalization
• Seed Dispersal
Most flowering plants use mutualism in
sexual reproduction.
• Plants need polinators such as bees or insects to carry their
seeds onto another plant.
• Both benefit as the polinator gets nectar and plants reproduce.
Methods used to induce short-day plants
to flower out of season.
• Since the plants are mostly used to darkness they need to be
covered from light.
• This can be done by putting a cloth over them for 15 hours a
day.
Drawing of seeds.
Drawing of animal polinated flowers.
Sources Used
• https://sites.google.com/a/canacad.ac.jp/sl-hl-1-biology-4ferguson/10-botany/9-3-growth-in-plants
• http://www.slideshare.net/smullen57/92-transport-in-the-phloemof-plants?next_slideshow=1
• http://www.slideshare.net/smullen57/ib-biology94-plantreproduction
• http://www.slideshare.net/smullen57/ib-biology-91-transport-in-thexylem-of-plants
• http://jxb.oxfordjournals.org/content/59/2/187.full