Land Plants

Question 1

When did land plants arrive

Answer 1

500mya

Question 2

Major events that changed earths atmosphere to allow for land plants

Answer 2

1. 2.8-2.2 mya: first oceans formed and atmosphere was full of nitrogen and methane. Cyanobacteria in oceans produced oxygen to transform air.
2. 650mya: snowball earth: green house gases used up by photo-synthesizers, resulting in more oxygen and extreme low temperatures.
3. 500mya: trilobites, mollusks, sea stars and urchins arrive as well as early plants.

Question 3

How did the transition from water to land happen..

Answer 3

Algae moved to end of water, and had to adapt to dessication=poikilohydric

Question 4

The flagellated cells of Charophyceae are distinct from other classes because…

Why is this important for land plants?

Answer 4

Asymmetrical flagellar root system of microtubules that anchor flagellum

Multilayered structure (MLS) is associated with one of the flagellar roots

Flagellated root system of Charophyceae with its MLS is very similar to that found in the sperm of bryophytes and some vascular plants. Therefore Charophyceae green algae are considered closest relative to bryophytes and vascular plants.

Question 5

Two orders of early land plants

Answer 5

Charales

Coleochaetales -surface or submerged rocks or plants; uninucleate cells, one large chloroplast with embedded Pyrenoid

Similar chloroplasts and Pyrenoids found in hornworts

Question 6

Coleochaete

Reproduction

Answer 6

Sexual reproduction is oogamous

Zygotes retained on female mat (gametophyte), similar to other embryophytes such as Chara and land plants

Protected by layer of somatic cells that grow around them

Develop placenta that enables material distribution to its gametes, that consists of cells secretory cells (transfer cells) similar to the placenta that connects the sporophyte and gametophyte generations of land plants

Question 7

Charales

Reproduction

Answer 7

-eggs borne in enclosed Oogonia, positioned in a position analogous to seedless plants
-close resemblance with sperm of bryophytes

Question 8

Charales characterisitc

Answer 8

-calcification of Oogonia with calcium carbonate provides good fossil record
-apical growth
-attached to the sediment with branching underground rhizoids

Question 9

Embryophyta

Answer 9

-constitute the terrestrial or land plants
-first representatives around 450mya
-shared with all terrestrial plants is retention of the embryo by the parent organism.

Question 10

Embryo coverage of coleochaete, Charales and terrestrial paints

Answer 10

Coleochaete: covers the embryo (but not around the ovule until it is fertilized)

Charales and all terrestrial plants cover both the ovule (before fertilization) and the embryo

Question 11

Modern embryophytes share the following traits with ancestors:

Answer 11

-a life cycle with alternation of generations
-apical cell growth
-cuticle
-multicellular antheridia and archegonia

Question 12

General features of bryophytes

Answer 12

-eukaryotic
-have chlorophyll a and b, xanthophylls and carotenoid pigments
-store starch
-pectin-cellulose walls
-mitosis is open (nuclear membrane disappears in mitosis)
-cytokinesis is by formation of a cell plate along a phragmoplast

Question 13

All bryophytes have a _____ life cycle that is ______

Answer 13

Sporuc
Oogamous

Question 14

_____, _______ and ______ are very similar to each other and fundamentally similar to flowering plants

Answer 14

Hepatophytes
Anthocerophytes
Bryophytes

Question 15

Rhizosphere

Answer 15

Volume of soil influenced by the root
-contains over 1000 microbial cells per gram of soil with over 30,000 microbial species

Roots and root hairs support intense chemical and biological activity in narrow area surrounding young roots

Question 16

Mycorrhizosphere

Answer 16

Rhizosphere with symbiotic mycorrhizal fungi associate with roots

Question 17

Why is mycorrhizal associations so important to plants?

Answer 17

Important to the acquisition of phosphorous from soul
-hyphae access inorganic nutrients from soil beyond the Rhizosphere
-scavenging role and active transport of low soluble forms of phosphorous (P) and Zn2+, Cu2+ and NH4+

Symbiotic sharing of carbohydrates (fructose and glucose) from plant

Question 18

Endomycorrhizae (arbuscular mycorrhiza)

Ectomycorrhizae

Answer 18

-Form symbiosis with 90% of vascular plants
-Fungal hyphae penetrate surface cells of roots (primary cortex)
-zygomycota

-High taxonomic diversity
-form symbiosis with 3% of plants (shrubs and trees=woody)
-large, fruiting bodies
-grows mantle around root but does not penetrate root with hypahe
-hyphae penetrate between root cells
-Basidiomycota and ascomycota

Question 19

In addition to the enhances nutrient uptake, different categories of mycorrhizae may protect roots against….

Answer 19

Pathogens, produce plant hormones and translocates carbohydrates between plants

Question 20

Mycorrhiza infection area occurs only on the….

Answer 20

Smallest order of secondary roots. These are the root tips that are still growing, elongating and increasing in girth. That is the only part of the root system that will absorb water and minerals.

-Very small part of root system of a plant which will be infected by the mycorrhizal fungus
-in all mycorrhizae only the cortical cells of the root are invaded by the fungus. (Between epidermis and vascular tissue)

Question 21

Species with _______ root hairs and _____ root hairs are not as dependent on mycorrhizae as species with _______ roots

Answer 21

Fine
Many

Taproot

Question 22

We’re terrestrial plants first to have mycorrhizal associations?

Answer 22

Nope, aquatic

Question 23

Mycorrhizal associations can also occur with plants without____

Answer 23

Roots (mosses and liverworts)

Question 24

Endo-mycorrhizae: arbuscualr mycorrhizae

How it works

Answer 24

-aseptate mycelium penetrates root and develops thick-walled, multi-nucleate vesicles
-hyphae fork repeatedly to form an arbuscule
-plant and fungal membranes remain separated by an apoplastic space (periarbuscular space)
-exchange of nutrients and water across periarbuscular space

Question 25

Chlamydospores

Answer 25

Large, Resting, asexual spores

Contain energy reserves (lipid, glycogen and proteins)

Survive in soil for many years

Only sexual reproduction known for this group

Important elements of soil food web

Reproducing and resting fungal spores to establish new mycelium

ENDO-mycorrhizae

Question 26

How do hyphae penetrate root cell walls in Endo-mycorrhizae

Answer 26

Hypahe penetrate root cell walls by mechanical pressure or cell-wall-degrading enzymes

Plant membrane extends to encase fungus branches—> fungus is surrounded by the cell membrane

Question 27

Metabolic activity and cytoplasm volume is higher in root cells with ______

Answer 27

Arbuscules

Periarbuscular space is highly acidic: ATPases in plasma memebranes of both partners set up protein gradient for active uptake of sucrose (fungus) and mineral nutrients (plant)

Question 28

Vesicular arbuscular mycorrhizae

Answer 28

Vesicles: thick walled oval structures contain large amounts of lipids and often numerous nuclei.

I’m dead root fragments, vesicles can be infective propagules and re-grow hyphae to infect new roots.

Question 29

What type of mycorrhizae is more recent

Answer 29

Ecto-mycorrhizae

Question 30

Ecto-mycorrhizae facilitate ______ and _____ transfer across individuals in a forest

Answer 30

Carbon
Nutrient

Survival of young trees enhanced when connected to a network of old trees

Question 31

Hartig net

Answer 31

Complex of fungal hyphae found in the intracellular spaces between the cortical cells of a root in ecto-mycorrhizae

Question 32

What other job do ecto-mycorrhizal fungal do

Answer 32

Decomposers

Fungal sheaths that form around the secondary root tips, accumulate minerals from the decomposing litter, before they are able to pass into the deeper mineral layers of the soil

Question 33

Infected ecto-mycorrhizae roots have what appearance

Answer 33

Short, pairs of branches

Question 34

Orchid mycorrhizae

Answer 34

-endomycorrhizae (mostly basidiomycota)
-all orchids infected with mycorrhizal fungus
-orchid seeds have small food reserve for the embryo and it is depleted by the time that the first few cell divisions of the embryo have occurred, therefore they depends on mycorrhizae.
-most orchid seeds do not germinate until the fungus symbiont penetrates seed coat of the seed.
-fungus supplies minerals and organic compounds to orchid like carbohydrates

Question 35

Many orchids are epiphytes meaning they live on plants rather than soil. How does mycorrhizal fungus work around this?

Answer 35

Fungus acts as a parasite upon the plant which the orchid is growing -> food is transferred by the fungus, from the tree, on which the orchid is growing, to the orchid.

Question 36

Ericaceous mycorrhizae

Answer 36

-formed by ascomycota fungi and plants in the family epacridaceae, ericaceae, pyrolaceae

-

Question 37

Ericoid mycorrhizae

Answer 37

Ericoid mycorrhizae have evolved in association with plants that are continually stressed by factors within the soil

Soul is typically extremely acidic, low in available minerals because of mineralization is inhibited.

Plants with Ericoid mycorrhizae have high tolerance to these stresses

Question 38

Where does Endo and ecto mycorrhizae go in a root

Answer 38

Endo-into epidermis-cortical cells-inside cortical cells

Ecto-into epidermis-inbetween cortical cells

Question 39

Arbuscular mycorrhizae are _______ mutualists

Answer 39

Obligate
Need partner plant root to germinate