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life study of
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

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
Stem
Transpiration Translocation
Lateral roots
The root system removes water and minerals from the soil environment. These solutes are transported to the shoot in the xylem tissue:
Transpiration
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 circulation: transpiration and translocation
©1996 Norton Presentation Maker, W. W. Norton & Company

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?
Let ’ s take a closer look at the vascular tissues
©1996 Norton Presentation Maker, W. W. Norton & Company

Monocot stem anatomy: vascular bundle
Translocation
Transpiration
©1996 Norton Presentation Maker, W. W. Norton & Company
Why must xylem do a lot more transport than phloem?

Dicot circulation: stem anatomy
Dicots start with one ring of bundles…
Let ’ s take a closer look at the vascular tissues
©1996 Norton Presentation Maker, W. W. Norton & Company

Dicot stem anatomy: vascular bundle
©1996 Norton Presentation Maker, W. W. Norton & Company phloem fibers
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

Dicot stem anatomy: vascular cambium adds secondary tissues
©1996 Norton Presentation Maker, W. W. Norton & Company
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!
xylem = wood
©1996 Norton Presentation Maker, W. W. Norton & Company

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

Dicot stem anatomy: 2-year old stem showing ray and periderm
©1996 Norton Presentation Maker, W. W. Norton & Company

Dicot stem anatomy: periderm dying epidermis maturing cork cells periderm cork cambium phelloderm cortical collenchyma cortical parenchyma
©1996 Norton Presentation Maker, W. W. Norton & Company

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.
©1996 Norton Presentation Maker, W. W. Norton & Company

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.
©1996 Norton Presentation Maker, W. W. Norton & Company

Dicot stem anatomy: xylem parenchyma, vessels, and tracheids
©1996 Norton Presentation Maker, W. W. Norton & Company

Dicot stem anatomy: xylem parenchyma, vessels, and tracheids
The huge vessel transports lots of water longitudinally, and shows lots of pits for lateral transport

Dicot stem anatomy: woody stem circulation
O
2 in and CO
2 out
©1996 Norton Presentation Maker, W. W. Norton & Company
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.

Xylem and Phloem: tissues with many cell types but conduction function
©1996 Norton Presentation Maker, W. W. Norton & Company

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: 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 gravity pulls water down atmospheric pressure keeps water in tube glass 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 ” medium 90 hours new growth black
Is phosphate uptake from soil: transpiration or translocation?
In xylem or phloem?
Is phosphate mobilization from lower leaf: transpiration or translocation?
In xylem or phloem?

Translocation: How solutes move in phloem
Leaf High Pressure plasmodesmata
Root
Low Pressure
Modified from: ©1996 Norton Presentation Maker, W. W. Norton & Company

Translocation: How solutes move bidirectionally in phloem
Low Pressure
Developing leaves, apical bud, flowers fruits
Leaf sugars amino acids
High
Pressure
Low Pressure
Modified from: ©1996 Norton Presentation Maker, W. W. Norton & Company
Lateral buds, stems, roots, root tip

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
Water and
Minerals
Apical bud
Axillary bud
Taproot
Figure 36-3 Page 793
Carbohydrate etc.
Branch
Stem
Transpiration Translocation
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).