View
38
Download
0
Category
Preview:
DESCRIPTION
BOT3015L Symbioses. Presentation created by Danielle Sherdan All photos from Raven et al. Biology of Plants except when otherwise noted. A continuum:. Symbiosis. Sym =together, bio =life. A network of interactions among organisms on a continuum between beneficial and detrimental effects. - PowerPoint PPT Presentation
Citation preview
BOT3015LSymbioses
Presentation created by Danielle SherdanAll photos from Raven et al. Biology of Plants except when otherwise noted
Symbiosis
Sym=together, bio=life
parasitism commensalism mutualism
A continuum:
A network of interactions among organisms on a continuum between beneficial and detrimental effects
A major driving force behind evolution
A few examples
• Flowering plants and pollinating animals• Humans and domesticated plants and animals• Humans and bacteria in their digestive system• Endosymbionts
• Origination of mitochondria and chloroplasts
Example of endosymbiosis
Vorticella (protozoan) under compound light microscope
One cell containing numerous autotrophic algal cells
Scanning electron microscope~5µm
Basic Outline of (Primary)
Endosymbiosisusing the plastid as
an example
Some debate about origin of outer membranes of plastids
The bulk of evidence indicates that all chloroplasts resulted from a single primary endosymbiotic event (=monophyletic origin of plastids) involving cyanobacteria. Modified from Outlaw lecture
A few examples
• Flowering plants and pollinating animals• Humans and domesticated plants and animals• Humans and bacteria in their digestive system• Endosymbionts
• Origination of mitochondria and chloroplasts• Plants and bacteria
• Rhizobia (also an example of endosymbiosis)
Symbioses between plants and bacteriaBacteria Example effect on plant physiology
Many are parasitic, but Rhizobium is mutualistic
RhizobiaSymbioses between plants and bacteria
Nitrogen Fixation
Legumes (and a few other plants) form a symbiosis with a nitrogen-fixing bacterium.
The bacterium enters the root and a nodule—part plant, part bacterium—is formed as a growth on the root.
From Outlaw lecture
RhizobiaSymbioses between plants and bacteria
Nitrogen Fixation
Benefit to the plant: Source of usable nitrogen, which is limiting to growth.
Benefit to the bacterium: Low O2 environment (O2 denatures nitrogenase) and source of reduced carbon.
From Outlaw lecture
Liposaccharides
Flavinoids
1. 2. 3.
4. 5.
Initiation of Rhizobium symbiosis at plant root
Modified from Outlaw lecture
Initiation of Rhizobium symbiosis at plant root
Rhizobia (arrows) attached to young root
hair
Bradyrhizobium on soybean (Glycine)Scanning electron micrograph ~5µm
Initiation of Rhizobium symbiosis at plant root
Root hair containing multiple infection threads (arrows)
Bradyrhizobium on soybean (Glycine)Differential-interference contrast photomicrograph ~20µm
Initiation of Rhizobium symbiosis at plant root
Bradyrhizobium on soybean (Glycine)Scanning electron micrograph
Infection thread with rhizobia
~1µm
Initiation of Rhizobium symbiosis at plant root
Bradyrhizobium on soybean (Glycine)Scanning electron micrograph
Groups of bacteroids surrounded by
membrane derived from infected root cell (uninfected cell in the above adjacent cell)
~2µm
Rhizobium symbiosis in dicot root nodule
Bradyrhizobium on soybean (Glycine)Compound light microscope
Cross section of mature root nodule. Rhizobia-
infected cells are stained dark.
Arrows indicate vascular bundles
~500µm
A few examples
• Flowering plants and pollinating animals• Humans and domesticated plants and animals• Humans and bacteria in their digestive system• Endosymbionts
• Origination of mitochondria and chloroplasts• Plants and bacteria
• Rhizobia (also an example of endosymbiosis)• Humans and fungi• Leafcutter ants and fungi• Lichens
LichensSymbiosis between fungus and population of unicellular or
filamentous algal or cyanobacterial cells
Interactions between lichens and animals exemplify the network nature of symbioses.
Reindeer moss (Cladonia)(note the misnomer)
Caloplaca
A few examples
• Flowering plants and pollinating animals• Humans and domesticated plants and animals• Humans and bacteria in their digestive system• Endosymbionts
• Origination of mitochondria and chloroplasts• Plants and bacteria
• Rhizobia (also an example of endosymbiosis)• Humans and fungi• Leafcutter ants and fungi• Lichens• Plants and fungi
• Mycorrhizae
Mycorrhizae
Myco=fungus, rhiza=root
• Fungus gets carbohydrates from plant
• Plant gets better nutrient absorption• Both have protective effects on the
other
Exposure to mycorrhizal fungi
White pine (Pinus)
__ +
Endomycorrhizaeendo=within
Branched fungal hyphae (arbuscules) invaginate the plasma membrane of sugar maple (Acer) root cells
Scanning electron micrograph ~10µm
EndomycorrhizaePawpaw and Glomales, an order of promiscuous endomycorrhizal
fungi
Fungi (stained blue to visualize)
Plant cell wall
The fungus does not penetrate the symplast.
Modified from Outlaw’s lecture
hypha
arbuscules
Mycorrhizaedooryard observation
Pawpaw (Asimina triloba)
From Outlaw’s garden
Ectomycorrhizae
Lodgepole pine (Pinus)
Fungus surrounds roots and grows between intercellular regions
Cross section of pine root with ectomycorrhizae
Notice how much surface area is added by the fungus
~50µm
TodayInvestigating mycorrhizae:
Comparative study of mycorrhizae in local plants
Work in groups of 2-3 to stain, observe, draw, and describe mycorrhizae in at least 3 different plant species
Draw and describe lichen and nodules without magnification, then section them, then draw them as they appear under the dissecting scope at a high magnification.
Recommended