Transcript 1001plants - Michigan State University

Plant Diversity
Fossilized plant spores
place plants on land
over 500 mybp.
Sporopollenin in cell wall
is the most durable
organic material known
C&R distinguish
Green Algae from Plants
by adaptations to terrestrial living
Plants and nearest relative green algae use chlorophyll a as photosynthetic pigment
& chlorophyll b as an accessory (catch photons at other colors - see ch 10)
Plants w/ chlorophyll look green
because chlorophyll does NOT absorb green
- it absorbs red and violet.
Photosynthesis uses light energy to
split H2O, release O2,
make ATP & NADPH, and
put the ‘hydrate’ in carbohydrate.
Fig 10.4
12H2O
6CO2
Fig 10.13
Fig 10.8
6O2
6H2O
1C6H12O6
Note reduced ratio
of red/(far-red) in shade:
Manipulative approaches to testing adaptive plasticity:
Phytochrome-mediated shade-avoidance responses
in plants. {see C&R ch 39}
Schmitt et al. 1999. AM NAT 154:S43-S54.
Because chlorophyll selectively absorbs red wavelengths,
the ratio of red (R) to far-red (FR) wavelengths
is an accurate signal {to phytochrome, Fig 39.20}
of vegetation shade and neighbor proximity.
Many plants respond to low R : FR with a suite
of photomorphogenic changes such as stem elongation,
suppression of branching, altered biomass allocation,
and accelerated flowering, commonly referred to as
the "shade avoidance syndrome".
Such responses are often elicited by FR reflected
from neighboring plants before canopy closure,
indicating that plants can detect and respond to
potential future competitors …
{bolt - race up high to compete for scarce light vs
branch – spread out low to collect abundant light}
C&R Fig 29.2:
Several lines of evidence suggest that
modern Chara (common pond algae)
is in sister group to modern plants.
{It is not the ancestor, any more than
chimps are ancestors to humans}
The cellulose-manufacturing rosettes found only
in the plasma membranes of charophyceans and land plants
are evidence of cell wall homology.
Charophyceans are the only algae with their anti-photorespiration
enzymes packaged in peroxisomes, as they are in plants.
Phragmoplasts occur during cell division
only in plants and charophyceans
Many plants have flagellated sperm, which match
charophycean sperm closely in ultrastructure.
Comparisons of chloroplast DNA place the charophyceans
as the green algae most closely related to land plants.
Molecular systematics of key nuclear genes for
cytoskeletal proteins support all the other evidence
connecting charophyceans and plants to a common ancestor.
Five derived characters unique to land plants.
1. apical meristems
In terrestrial habitats, the resources
that a photosynthetic organism needs
are found in two very different places.
Light and carbon dioxide
are mainly available aboveground;
water and mineral nutrients
are found mainly in the soil.
Thus, the complex bodies of plants show
varying degrees of structural specialization
for subterranean and aerial organs
- roots and leaf-bearing shoots …
Though plants cannot move from place to place,
the elongation and branching
of their shoots and roots maximize their
exposure to environmental resources.
This growth in length is sustained
by the activity of apical meristems
localized regions of cell division at the tips of
shoots and roots
Fig 35-12. Apical meristems near the tips of roots and shoots
are responsible for primary growth in length.
Woody plants also have lateral meristems that function in secondary growth.
Five derived characters unique to land plants.
2. “the embryophyte condition”
Multicellular plant embryos
develop from zygotes that are retained
within tissues of the female parent.
The parental tissues provide the developing embryo
with nutrients, such as sugars and amino acids.
The embryo has specialized placental transfer cells …
This interface is analogous to
the nutrient-transferring embryo-mother interface
of eutherian (placental) mammals.
Land plants are also known as embryophytes,
a distinction that recognizes
multicellular, dependent embryos
as a derived characteristic common to the land plants.
{note: only seed plants package these embryos
into a seed}
embryophytes
Five derived characters unique to land plants.
3. Alternation of generations
two multicellular body forms alternate,
diploid sporophytes &
haploid gametophytes,
each form producing the other.
Alternation of generations
is a special type of
haploid - diploid sexual cycle
w/ both stages represented
by multicellular bodies.
C&R Fig 30.1
In bryophytes,
the gametophyte is larger and more conspicuous.
In pteridophytes, gymnosperms, and angiosperms
the sporophyte form is the dominant.
The fern plant most of us are familiar with
is the diploid sporophyte.
The gametophyte is a tiny plant.
In gymnosperms & angiosperms
the gametophyte is retained within the sporophyte.
Five derived characters unique to land plants.
4. Walled spores {in flowering plants - pollen}
Plant spores are haploid reproductive cells,
produced by the diploid sporophyte sporangia,
that grow into
multicellular, haploid gametophytes by mitosis.
This chemical adaptation makes it possible for
wind-carried spores {pollen} to disperse
through dry air without harm.
All four major plant groups produce spores.
Fossilized plant spores
place plants on land
over 500 mybp.
Sporopollenin in cell wall
is the most durable
organic material known
5. Multicellular gametangia …
note sperm need water film to swim to egg
C&R Fig 30.1
C&R
Fig
29.16
Life cycle w/ alt of gen
in Bryophytes
sporophyte (2n)
sphagnum - future peat
moss
Gametophyte (n)
dominates
liverwort
hornwort
Pteridophytes: Seedless Vascular Plants
w/ a little independent gametophyte
‘homosporous condition’
C&R Fig 29.23
Life cycle w/ alt of gen
in Ferns
- note sperm need
water film to swim to egg
division Pterophyta - ferns
ground pines
or club mosses
whisk ferns
horsetails
ferns
C&R Fig 30.1
Seed plants are vascular plants that produce seeds.
The two clades of seed plants
are gymnosperms and angiosperms
Three important reproductive adaptations:
reduction of the gametophyte,
the advent of the seed,
and the evolution of pollen.
C&R Fig 30.1
Vascular Seed Plants - Gymnosperms
Life cycle w/ alt of gen
in Pine
C&R Fig 30.9
wind-blown pollen
Sporophyte dominates
seed
> year after
pollination
wind-blown pollen
- works in dry air
- no swimming sperm
Gymnosperms: Conifers +
http://taggart.glg.msu.edu/bot335/cycads.htm
Although
significant elements of Mesozoic vegetation,
cycads today are represented by only 10 genera,
confined to the semi-arid tropics and subtropics.
Mexico has the highest diversity of living cycads.
http://daphne.palomar.edu/wayne/plapr96.htm#ginkleaf
The unique, fan-shaped leaves and naked seeds of living
Ginkgo biloba trees
have changed very little in more than 200 million years.
Although the naked, stalked seed resembles a cherry,
IT IS NOT A FRUIT!
The perfectly preserved cell structure of 15 million-year-old Ginkgo beckii wood
http://www.botany.utoronto.ca/courses/BOT307/D_Families
gnetophytes Welwitschia Hook. f., monotypic genus
of the deserts of Namibia and southern Angola.
Plants are adapted to terrestrial/air env:
separation of light (and CO2) from soil nutrients & water - distribution problems:
Fig 36.1,11; lignin, vascular
system etc {wood is former plumbing}
Vascular Flowering Seed Plants
- Angiosperms
Life cycle w/ alt of gen
in ‘a
flower’
often carried by an animal
C&R Fig 30.17
seed
self incompataiblity
C&R Fig 38.7
http://hortwww-2.ag.ohiostate.edu/hcs/TMI/hcs200/seed.html
Double fertilization: also in gnetophytes
1. of 1n egg: diploid 2n zygote
2. of 2x1n double haploid cell:
triploid 3n endosperm (food)
… tomatoes, as well as squash,
strawberries, water melons,
peanuts and wheat are all fruits,
according to the
definition of a fruit
as a mature ovary
{all angiosperms
produce their seeds
inside a ‘fruit’}
Plant Manipulation
Digestion And Dispersal
…
Many plants have ripe, fleshy, coloured fruit
scientists observed … animals living around
in order to attract animals that will eat them
a group of wild-growing chillies in Arizona. …
and then disperse their seeds in droppings.
desert mice and rats avoided spicy chillies,
However, the chilli plant has developed
but birds fed almost exclusively on the plants.
another way of ensuring its seeds
{the vanilloid receptor subtype 1 (VR1) in birds
are spread far and wide.
does NOT react w/ capsaicin}
… when birds ate the chillies,
What raises the roof of your mouth when you
many seeds germinated,
eat a chilli is a substance called capsaicin.
but there was no germination
This stimulates the areas of the skin and tongue after mice had eaten the chilli seeds.
that normally sense intense heat and pain,
falsely telling the brain that the area affected
… seeds pass through a birds’ digestive systems
is burning.
very quickly and come out unharmed,
whereas in mice, rats and other mammals,
New research carried out by scientists
the seeds don’t make it out in one piece …
in Arizona, has discovered that
this characteristic peppery taste
The researchers suggest that chilli plants
repels certain animals {mammals}
have evolved to produce capsaicin
– which are no good at dispersing the seeds.
as a repellent for animals {mammals} …
whilst still allowing birds to eat their seeds.
Seed dispersal –
Directed deterrence by capsaicin in chillies.
Tewksbury JJ, Nabhan GP
NATURE 412 (6845): 403-404 JUL 26 2001
Molecular basis for species-specific sensitivity to "hot" chili peppers.
Jordt SE, Julius D . CELL 108 (3): 421-430 FEB 8 2002
Abstract:
Chili peppers produce the pungent vanilloid compound capsaicin,
which offers protection from predatory mammals.
Birds are indifferent to the pain-producing effects of capsaicin
and therefore serve as vectors for seed dispersal.
Here, we determine the molecular basis for this species-specific behavioral response
by identifying a domain of the rat vanilloid receptor
that confers sensitivity to capsaicin to the normally insensitive chicken ortholog.
Our findings provide a molecular basis
for the ecological phenomenon of directed deterrence
and suggest that the capacity to detect capsaicin-like inflammatory substances
is a recent acquisition of mammalian vanilloid receptors. {then exploited by chilli peppers}
Coevolution w/ pollinators:
Pollination Syndromes
C,R&M Fig 30.9
http://farrer.csu.edu.au/ASGAP/APOL15/sep99-1.html
Some relationships
between
flower shape,
pollination vector
and flower colour
http://bio.fsu.edu/~winn/3402L/WinnCH4.html
Bee eyes have trichromatic vision … sensitive to green, blue, or ultraviolet.
Bees are blind to red. Typical bee flowers are open in the daytime,
have a minty fragrance, and offer their visitors nectar, pollen, or both.
… are brightly colored (often yellow or blue) … but are not red.
Butterflies are sun lovers that like to perch while feeding.
They have long and slender probosces,
can perceive a wide spectrum of colors,
and have an excellent sense of smell.
With few exceptions, they are nectar feeders.
… typical butterfly-pollinated flowers are open in the daytime, possess a long, thin
corolla tube … and are generally vividly colored (often red), although sometimes
white.
They also provide their butterfly visitors with a platform to land and walk on.
Birds have excellent color vision and appear to favor red.
… their sense of smell is very poor.
Bird-pollinated flowers have no odor.
The amount of nectar produced can be quite large, up to a cupful a day
The colors … vary enormously. Many are red, but others are yellow
or blue or almost any other color. … bird pollinated flowers are generally open all day.
… corollas are often tubular (and are larger in diameter than butterfly flowers)
Moths: Hawkmoths, also known as sphinx moths
htm#manduca2.gif
are the nocturnal counterparts of hummingbirds.
… normally feed on the wing, … quite large, fly at high speeds …
like warm blooded animals, having higher energy requirements …
can consume a good teaspoon of nectar at a single sitting.
… equipped with a long, thin, and very flexible proboscis
http://daphne.palomar.edu/wayne/manduca2.
… flowers that cater to hawkmoths
open in the evening and are extremely fragrant.
They are snow-white or light-colored, offer no landing platform …
Many have both visual and olfactory nectar guides.
The corolla tube is long and narrow, a feature that discriminates short-tongued
visitors,
and nectar is abundant.
http://bio.fsu.edu/~winn/3402L/WinnCH4.html
… a number of flies and beetles
are not really adapted to flowers at all
(although the flowers are adapted to them!).
These are the carrion, dung, and mushroom flies and beetles
that are {tricked} trapped by various flowers or inflorescences.
Species in this group are primarily attracted by smell.
Some are looking for food, others are looking for egg-laying sites.
In either case, they are tricked by the flower odor into thinking
that they have found their normal prey.
They … figure out that they have been fooled, then move on.
Common traits of the flowers that use such pollinators include
dull colors, often large, open flowers,
Symplocarpus foetidus
(although some species instead have enclosures,
(skunk cabbage)
which trap the pollinator for a time),
and distinct odors, which are sometimes quite unpleasant to humans.
http://web.ngdc.noaa.gov/paleo/image/gsafinal.gif
Ranges of
Most pollen misses its target.
white pine If it falls into anaerobic,
acidic bogs, it fossilizes.
hickory
Core & construct pollen profiles:
from pollen
shows the surrounding plant community.
record Date the strata with carbon-14 dating.
Pollen profile
Shelton Mastodon Site
(Oakland County, Michigan)
http://www.calvin.edu/academic/geology/mastodon/shel2.htm
Carbon date:
 9.6kybp
 11 kybp
Global warming?
Grasses are flowering plants
http://fwkc.com/encyclopedia/low/articles/g/g010000624f.html
Most grasses are pollinated by wind, so that their flowers are highly reduced …
All the world's cereal crops are grasses.
The world's 5 top crops produce more tonnage than the next 25 combined, and
4 of the top 5 are the cereals rice, wheat, corn, and barley.
Human well-being depends on these few grasses,
Grasses are the primary source of food for domestic and wild grazing animals …
The total land area devoted to these kinds of croplands
is greater than the land area for all other kinds of croplands combined.
Another economically significant use of grasses is lawns …
grasses are well adapted for use in lawns, because their
basal meristems (growing points) are not lost with mowing.
{or grazing, or burning - used in prairie restoration}
http://www.colostate.edu/Depts/CoopExt/PUBS/NATRES/06108.html
Grass plants and grazing mammals
appeared in the fossil record
at the same time
in the lower Miocene Epoch about
20 million years ago. {recent!}
Grass plants, grazing mammals,
and grassland plant communities
have evolved together.
Prairie Meadows Burning
by George Catlin
Plants are sensitive!
Fig 39-26.
Altering gene expression by touch in Arabidopsis .
The shorter plant on the left was touched twice a day.
{hiding from grazers?}
The unmolested plant (right) grew much taller.
Calmodulin as a versatile calcium signal transducer in plants.
Snedden WA, Fromm H. 2001. NEW PHYTOLOGIST 151: 35-66.
… This review summarizes current knowledge
of the Ca2+-calmodulin messenger system in plants
and presents suggestions for future areas of research.
Induced defenses:
Plants facultatively allocate more to defense after attack.
http://entomology.wisc.edu/~raffa/rafres.html
(a) Chemical change in pines during (b) Bark beetle killed by
induced defensive response.
induced defensive response
… and warn their neighbors!
(“Talking Trees”)
see: http://dogbert.gi.alaska.edu/ScienceForum/ASF7/762.html
Sometimes they call for help!
Herbivory, induced resistance,
and interplant signal transfer in Alnus glutinosa.
Tscharntke et al. 2001.
Biochemical Systematics and Ecology 29:1025-1047.
Abstract:
Field experiments with manually defoliated black alders (Alnus glutinosa)
showed that defoliation affected herbivory by the major alder antagonist,
the leaf beetle Agelastica alni.
Herbivore damage increased
with increasing distance to the defoliated tree,
suggesting induced resistance not only on the damaged tree,
but also on the neighbouring trees.
The beetles also avoided leaves
from the nearest neighbours
Fig. 1. Number of individuals
for both feeding and oviposition of phytophagous arthropods
on the defoliated trees,
in a laboratory assay,
their nearest neighbours
so the alders showed
and their farthest neighbours
interplant resistance transfer.
(0, 1.3 and 10.6 m distance to the
Natural enemies did not appear
manually defoliated tree),
81 days after defoliation …
to shape this pattern, …
(b) phytophagous specialists:
F=6.43, n=30, p<0.005.
Tscharntke et al.
Mechanisms causing this pattern, found in the field,
were studied in more detail using biochemical analyses and further bioassays.
Responses of alder leaves to herbivory of A. alni were shown to include
ethylene emission and the release of a blend of volatiles
with mono-, sesqui- and homoterpenes. …
jasmonic acid (JA) showed the activation … following herbivory.
Further evidence that airborne interplant communication may be important
in the response of alder trees to beetle attack came from container experiments,
In airtight chambers,
unattacked leaves significantly increased
the activity of proteinase inhibitors
when they were associated with leaves
previously attacked by beetle larvae.
… the relative importance of airborne and
possible soil-borne signals
as well as unknown effects of
intensified nutrient absorption of defoliated trees,
possibly reducing foliage quality
of undamaged neighbours,
remains to be shown.
Herbivore-infested plants selectively attract parasitoids
De Moraes et al. 1998. NATURE 393:570-573.
Abstract: In response to insect herbivory,
plants synthesize and emit blends of volatile compounds
from their damaged and undamaged tissues,
which act as important host-location cues for parasitic insects.
Here we use chemical and behavioural assays to show that
these plant emissions can transmit herbivore-specific information
that is detectable by parasitic wasps (parasitoids).
Tobacco, cotton and maize plants each produce distinct volatile blends
in response to damage by two closely related herbivore species,
Heliothis virescens {tobacco budworm} and Helicoverpa zea {corn earworm}.
The specialist parasitic wasp Cardiochiles nigriceps exploits these differences
to distinguish infestation by its host, H. virescens, from that by H. zea.
The production by
phylogenetically diverse plant species and
the exploitation by parasitoids of highly specific chemical
signals, keyed to individual herbivore species,
indicates that the interaction between plants and
the natural enemies of the herbivores that attack them
is more sophisticated than previously realized.
Polydnavirus-mediated suppression of insect immunity.
Shelby KS, Webb BA. 1999. Journal Of Insect Physiology 45: 507-514.
bstract:
Polydnaviruses are symbiotic proviruses of some ichneumonid and braconid wasps
that modify the physiology, growth and development of host lepidopteran larvae.
Polydnavirus infection targets neuroendocrine and immune systems, altering
behavior, stunting growth, and immobilizing immune responses to wasp eggs and
larvae. Polydnavirus-mediated disruption of cellular and humoral immunity renders
parasitized lepidopteran larvae suitable for development of wasp larvae as well as
more susceptible to opportunistic infections.
…the unique genomic organization of polydnaviruses may have evolved to amplify
the synthesis of immunosuppressive viral proteins. …
from deBuron & Beckage,
1992.