Transpiration and Translocation

Transcript Transpiration and Translocation

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Biology:

life study of

What is Life?

Properties of Life Cellular Structure:

the unit of life, one or many

Metabolism:

photosynthesis, respiration, fermentation, digestion, gas exchange, secretion, excretion, circulation--processing materials and energy

Growth:

cell enlargement, cell number

Movement:

intracellular, movement, locomotion

Reproduction:

avoid extinction at death

Behavior:

short term response to stimuli

Evolution:

long term adaptation

Organismal Circulation

Unicellular Organisms Autotrophic Multicellular Organisms (Heterotrophic Multicellular Organisms)

Cyclosis

in

Physarum polycephalum

, a slime mold

This organism consists of one very large cytoplasm (plasmodium) with many nuclei and food vacuoles in the cytosol (coenocytic).

Slime molds can weigh up toward kilogram range and move their blob-like mass around exclusively by cyclosis.

http://botit.botany.wisc.edu/courses/img/Botany_ 130/Movies/Slime_mold.mov

Here you can see, in a thin region of cytoplasm, that it moves along pathways that are river-like in appearance.

Transport is NOT always unidirectional.

The correct taxonomic affiliation is unclear.

It has been treated as Fungus and Protist.

Further study is needed to resolve its position.

What is the ATP source?

Cyclosis:

cytoplasmic streaming…intracellular circulation

Elodea canadensis

Chloroplasts and other organelles have surface proteins with myosin-like activity.

Microfilaments of actin are found just under cell membrane.

http://www.microscopy-uk.org.uk/mag/imgnov00/cycloa3i.avi

What is the source of ATP?

ATP and Calcium allow myosin to slide along actin filaments, resulting in circulation of organelles within the cell.

Can you be more specific?

If light intensity were reduced, what would be the prediction based on your hypothesis?

Figure 36-3 Page 793 The shoot organ system is photoautotrophic, taking in CO 2 releasing O daylight.

2 and in Diffusion is sufficient to exchange gases. But solutes need to be circulated in the large plant body as diffusion is too slow!!

The root organ system is chemoheterotrophic, taking in O 2 and releasing CO 2 in the darkness of the soil environment.

Node Internode Node Leaves Stem Apical bud Axillary bud

CO 2 in and O 2 out

Branch

O 2 in and CO 2 out

Lateral roots Taproot

O 2 in and CO 2 out

Figure 36-3 Page 793 The shoot system produces carbohydrates (etc.) by photosynthesis. These solutes are transported to the roots in the phloem tissue:

Translocation Node Internode Node Leaves Apical bud Axillary bud Carbohydrate etc.

Branch

The root system removes water and minerals from the soil environment. These solutes are transported to the shoot in the xylem tissue:

Transpiration Stem Transpiration Translocation Lateral roots Water and Minerals Taproot

Figure 36-3 Page 793 Because these pathways involve solutes in water passing in the adjacent tissues of a narrow vascular bundle, this is a circulation system!

Transpiration and Translocation

The water is moving up the xylem, and down the phloem, making a full circuit!

Node Internode Node Leaves Apical bud Axillary bud Carbohydrate etc.

Branch Stem Transpiration Translocation Lateral roots Water and Minerals Taproot

Figure 36-18 Page 802 Plants occur in two major groups (and some minor ones) They differ, in part, in their circulation systems:

Cross section of a eudicot stem Cross section of a monocot stem Epidermis Cortex Pith Ground tissue Vascular bundles

Dicots initially have one ring of vascular bundles Monocots rapidly develop multiple, concentric, rings of vascular bundles

Monocot stem anatomy

Young Monocot Mature Monocot vascular bundles As a monocot plant grows in diameter, new bundles are added toward the outside for increased circulation to the larger plant body.

Monocot stem anatomy Is this slice from a young or a mature part of the corn stem?

Monocot stem anatomy: vascular bundle

Translocation Transpiration

Support of Stem

functional phloem

Translocation

vascular cambium

Cell Divison: More Xylem and Phloem

xylem

Transpiration

As a dicot grows, how does it add vascular capacity to become a tree?

Dicot stem anatomy: vascular cambium adds secondary tissues epidermis cortex 1º phloem 2º phloem cambium 2º xylem 1º xylem pith

Each year the vascular cambium make a new layer of secondary xylem and secondary phloem

Dicot stem anatomy: four year-old stem (3 annual growth rings) phloem etc. = bark

All of these tissues were added by the vascular cambium!

Figure 36.29 Page 810 See also part (a)

cambium phloem or less competition in forest?

or more competition in forest?

Figure 36.0 Page 791

periderm phloem cambium = bark

heartwood pith

Two Xylem Conducting Cells: tracheid developmental sequence Annular Helical Pitted When flowering plants are young, water needs are limited, tracheids suffice.

The walls are strengthened with secondary thickenings including lignin.

Protoxylem have stretchable annular or helical thickenings.

Metaxylem have reticulate or pitted and fully rigid walls.

Tracheids have end walls and flow between cells is through pits.

Dicot stem anatomy: xylem vessel evolution plesiomorphic apomorphic As flowering plants age and grow, water needs increase, and tracheids need to be supplemented.

Flowering plants evolved xylem cells with larger cell diameter and perforated end walls to increase water flow.

Vessels have perforated end walls or lack end walls, but lateral flow between cells is still through pits.

Dicot stem anatomy: xylem parenchyma, vessels, and tracheids

The huge vessel transports lots of water longitudinally, and shows lots of pits for lateral transport

This sketch is showing the importance of lateral transport.

In both transpiration and translocation materials must move radially to the interior and to the exterior as well as up and down the plant.

Secondary xylem: cross sections of three species

Vessels, Tracheids have different distribution patterns.

Some produce big vessels only in spring wood Others produce vessels year-round.

Mendocino Tree (Coastal Redwood)

Sequoia sempervirens

Ukiah, California 112 m tall (367.5 feet)!

This tree is more than ten times taller than is “ theoretically possible ” based solely upon the length of the column of uncavitated water.

How could this be achieved?

http://www.nearctica.com/trees/conifer/tsuga/Ssemp10.jpg

Transpiration in a tall tree has at least 3 critical components:

Evaporation: pulling up water from above Capillarity: climbing up of water within xylem Root Pressure: pushing up water from below

Transpiration: root pressure (osmotic “ push ” )

guttation

This is not “ dew ” condensing!

Solutes from translocation of sugars accumulate in roots.

Water from the soil moves in by osmosis.

Accumulating water in the root rises in the xylem.

Water escapes from hydathodes.

Transpiration: root pressure (osmotic “ push ” ) The veins (coarse and fine) show that no cell in a leaf is far from xylem and phloem (i.e.water and food!).

The xylem of the veins leaks at the leaf margin in a modified stoma called the hydathode.

http://img.fotocommunity.com/photos/8489473.jpg

These droplets are xylem sap.

Root pressure accounts for maybe a half-meter of “ push ” up a tree trunk.

Capillarity: maximum height of unbroken water column

glass tube gravity pulls water down atmospheric pressure keeps water in tube vacuum created 10.4m

The small diameter of vessels and tracheids and the surface tension of water provide capillary (

“

climb

”

Cohesion of water, caused by hydrogen bonds, helps avoid cavitation.

water

A tree taller than 10.4 m would need some adaptations to avoid

“

cavitation

”

Dicot stem anatomy: pine xylem tracheids with pits, xylem rays tracheids with pits ray parenchyma ©1996 Norton Presentation Maker, W. W. Norton & Company In spite of the limitations of tracheids-only xylem, conifers are among the tallest of trees!

Conifer stem anatomy: bordered pits as “ check-valve ” for flow secondary wall primary wall middle lamella pit aperture pit membrane pit border torus pit chamber These pit features allow conifers to be very tall and still avoid cavitation in their xylem cells.

P low P high

As pressures change between adjacent cells, the torus movement blocks catastrophic flow that would result in cavitation.

Transpiration: evaporation ( “ pull ” ) Water evaporating from a porous clay cap also lifts the mercury!

water mercury Transpiration can lift the mercury vacuum above its normal cavitation height!

76 cm mercury

Grown in 32 PO 4 (radioactive phosphorus) 1 hour “ Cold ” medium 6 hours “ Cold new growth black ” medium 90 hours Is phosphate uptake from soil: transpiration or translocation?

In xylem or phloem?

Is phosphate mobilization lower leaf: from transpiration or translocation?

In xylem or phloem?

Translocation: How solutes move in phloem

Leaf High Pressure plasmodesmata Root Low Pressure

Translocation: How solutes move bidirectionally in phloem

Low Pressure

Developing leaves, apical bud, flowers fruits Leaf sugars amino acids

High Pressure Low Pressure

Transpiration Evaporation:

Water evaporates from mesophyll into atmosphere.

Water molecules are pulled up the xylem by virtue of cohesion.

Capillarity:

Water climbs in the xylem cell walls by adhesion.

Water molecules follow by cohesion.

Root Pressure:

Water moves into the root because of solutes from phloem.

Pressure pushes the water up the stem.

Node Internode Node Leaves Stem Transpiration Translocation Water and Minerals Apical bud Axillary bud Taproot

Figure 36-3 Page 793

Carbohydrate etc.

Branch Lateral roots

Node Internode Node Leaves Stem Transpiration Water and Minerals Apical bud Axillary bud Carbohydrate etc.

Branch Translocation Taproot

Figure 36-3 Page 793

Lateral roots Translocation Leaf = Source

Photosynthesis produces solutes.

Solutes loaded into phloem by active transport.

Water follows by osmosis, increasing pressure.

Root (etc.) = Sinks

Solutes removed from phloem by active transport.

Water follows by osmosis, reducing pressure.

Pressure = Bulk Flow

The pressure gradient forces phloem sap away from leaves to all sinks (bidirectionally).