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Biology: What is Life? 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

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. 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. http://botit.botany.wisc.edu/courses/img/Botany_130/Movies/Slime_mold.mov 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. ATP and Calcium allow myosin to slide along actin filaments, resulting in circulation of organelles within the cell. http://www.microscopy-uk.org.uk/mag/imgnov00/cycloa3i.avi What is the source of ATP? Can you be more specific? If light intensity were reduced, what would be the prediction based on your hypothesis?

Figure 36-3 Page 793 Apical bud The shoot organ system is photoautotrophic, taking in CO2 and releasing O2 in daylight. Axillary bud Node CO2 in and O2 out Internode Node Shoot system Leaves Branch O2 in and CO2 out Diffusion is sufficient to exchange gases. But solutes need to be circulated in the large plant body as diffusion is too slow!! Stem Lateral roots The root organ system is chemoheterotrophic, taking in O2 and releasing CO2 in the darkness of the soil environment. Root system O2 in and CO2 out Taproot

Carbohydrate etc. Transpiration Translocation Water and Minerals Figure 36-3 Page 793 Apical bud The shoot system produces carbohydrates (etc.) by photosynthesis. These solutes are transported to the roots in the phloem tissue: Translocation Axillary bud Node Carbohydrate etc. Internode Node Shoot system Leaves Branch Stem Transpiration Translocation The root system removes water and minerals from the soil environment. These solutes are transported to the shoot in the xylem tissue: Transpiration Lateral roots Root system Water and Minerals Taproot

Carbohydrate etc. Transpiration Translocation Water and Minerals Figure 36-3 Page 793 Apical bud Axillary bud Node Carbohydrate etc. Internode 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 Shoot system Leaves Branch Stem Transpiration Translocation Lateral roots Root system Water and Minerals Taproot

Plants occur in two major groups (and some minor ones) 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 Ground tissue Pith 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

Monocot stem anatomy Mature Monocot Young 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.

Is this slice from a young or a mature part of the corn stem? Monocot stem anatomy Let’s take a closer look at the vascular tissues ©1996 Norton Presentation Maker, W. W. Norton & Company

Why must xylem do a lot more transport than phloem? 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

Cell Divison: More Xylem and Phloem Dicot stem anatomy: vascular bundle 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? ©1996 Norton Presentation Maker, W. W. Norton & Company

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

cambium phloem or less competition in forest? Figure 36.29 Page 810 See also part (a) or less competition in forest? or more competition in forest? cambium phloem

sapwood heartwood pith periderm phloem cambium = bark Figure 36.0 Page 791 periderm phloem cambium = bark sapwood 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 ©1996 Norton Presentation Maker, W. W. Norton & Company The huge vessel transports lots of water longitudinally, and shows lots of pits for lateral transport

Dicot stem anatomy: woody stem circulation 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. O2 in and CO2 out ©1996 Norton Presentation Maker, W. W. Norton & Company

Secondary xylem: cross sections of three species ©1996 Norton Presentation Maker, W. W. Norton & Company 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 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”) 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. guttation ©1996 Norton Presentation Maker, W. W. Norton & Company This is not “dew” condensing!

Transpiration: root pressure (osmotic “push”) http://img.fotocommunity.com/photos/8489473.jpg 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. 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 vacuum created 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. A tree taller than 10.4 m would need some adaptations to avoid “cavitation” gravity pulls water down 10.4m atmospheric pressure keeps water in tube water

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

Conifer stem anatomy: bordered pits as “check-valve” for flow secondary wall primary wall middle lamella pit aperture pit membrane These pit features allow conifers to be very tall and still avoid cavitation in their xylem cells. As pressures change between adjacent cells, the torus movement blocks catastrophic flow that would result in cavitation. pit border torus pit chamber P low P high

Transpiration: evaporation (“pull”) Transpiration can lift the mercury above its normal cavitation height! vacuum water mercury Water evaporating from a porous clay cap also lifts the mercury! 76 cm mercury

Grown in 32PO4 (radioactive phosphorus) 1 hour “Cold” medium 6 hours “Cold” medium 90 hours new growth black ©1996 Norton Presentation Maker, W. W. Norton & Company note: fading Is phosphate mobilization from lower leaf: transpiration or translocation? In xylem or phloem? Is phosphate uptake from soil: transpiration or translocation? In xylem or phloem?

Translocation: How solutes move in phloem Leaf High Pressure plasmodesmata Root active transport 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 Lateral buds, stems, roots, root tip Low Pressure Modified from: ©1996 Norton Presentation Maker, W. W. Norton & Company

Transpiration Carbohydrate etc. Transpiration Translocation Apical bud Axillary bud Node Evaporation: Water evaporates from mesophyll into atmosphere. Water molecules are pulled up the xylem by virtue of cohesion. Carbohydrate etc. Internode Node Shoot system Leaves Branch Capillarity: Water climbs in the xylem cell walls by adhesion. Water molecules follow by cohesion. Stem Transpiration Translocation Lateral roots Root Pressure: Water moves into the root because of solutes from phloem. Pressure pushes the water up the stem. Root system Water and Minerals Taproot Figure 36-3 Page 793

Translocation Carbohydrate etc. Transpiration Translocation Apical bud Axillary bud Node Leaf = Source Photosynthesis produces solutes. Solutes loaded into phloem by active transport. Water follows by osmosis, increasing pressure. Carbohydrate etc. Internode Node Shoot system Leaves Branch Stem Transpiration Translocation Root (etc.) = Sinks Solutes removed from phloem by active transport. Water follows by osmosis, reducing pressure. Lateral roots Root system Pressure = Bulk Flow The pressure gradient forces phloem sap away from leaves to all sinks (bidirectionally). Water and Minerals Taproot Figure 36-3 Page 793