Chapter 25: Seedless Plants

Plants share a common ancestor with ___________ in the _______ supergroup of eukaryotes.

Plants share a common ancestor with ___________ in the _______ supergroup of eukaryotes.

Plants share a common ancestor with charophytes (green algae) in the archaeplastida supergroup of eukaryotes.

What are the shared characteristics between green algae and plants

• Chlorophytes, Charophytes & Plants share:

  • multicellularity

  • cell walls with cellulose

  • chloroplasts with same pigments (chlorophyll. a & b)

  • storage molecule is starch

What is desiccation, what needs to be protected , and how do plants adapt?

• Desiccation, or drying out, is a constant danger for an organism exposed to air

• Both gametes and zygotes must be protected from desiccation

• Plants need to develop structural support in a medium that does not give the same lift as water

• The male gametes must reach the female gametes using new strategies, because swimming is no longer possible

What is the advantage for plants on land?

• [CO2] higher

• light intensity higher

• more minerals

• no “herbivores”

• no competition

what is the disadvantage of plants in air?

• risk of desiccation (both adult & gametes)

• no “support” in air

What adaptations did plants make from water to land?

• Life cycle in all land plants exhibits the alternation of generations

• An apical meristem tissue in roots and shoots

• Evolution of a waxy cuticle to resist desiccation

• Cell walls with lignin to support structures off the ground.

Describe how plants have an alternation of generations

2n and n muticellular forms

Fill in the blank

How does the plant life cycle differ from the charophyte life cycle

• only multicellular is haploid

• zygote does meiosis to produce only 4 diverse offspring

• only 4 recombinant spores

• only one cell; does meiosis

• NOT alternation of generations

Where are haploid spores dispersed and made?

• dispersal thru air: sporopollenin protects

• made within multicellular sporangium

How do seedless plants protect sperm and in what structure?

• Multicellular gametangia

  • protecting sperm w/in antheridium

How do seedless plants protect eggs? What happens in this structure?

• egg protected within archegonium

• fertilization here: forming zygote

What is the Apical Meristem and where is it located. What function does it provide?

• plant root and shoots

• continuously dividing cells

• roots & shoots grow toward resources

Describe how the outer layer of plants help in protection and function?

• waxy coat stops desiccation

• pores needed to allow CO2/O2 exchange

  • controllable stomata in most plants

What do plants produce to deter, repel or poison competitors, herbivores, & parasites

chemicals called secondary metabolites

What is Mycorrhizae and when does it date back to?

• mutualism with fungi; helps water & mineral absorption

• dates back to first land plants (before true roots)!

What are seedless, non vascular plants called and give 3 examples.

• Collectively referred to as “Bryophytes”

• EX: Hepaticophyta (Liverworts), Anthocerotophyta (Hornworts), Bryophyta (Mosses)
  

What are some Bryophyte Characteristics relating to its haploid gametophyte? What does it make? Where does it grow?

• Haploid gametophyte is dominant form:

• Dominant=longest lasting or largest

• makes eggs & flagellated sperm

• most are small, low growing, moist areas

What are some Bryophyte Characteristics relating to its Diploid sporophyte? What is its relationship with the gametophyte? Where does it grow and what does it make?

• Diploid sporophyte depends on gametophyte for food & water

• grows within archegonium of gametophyte

• sporangium makes many haploid spores

What do the gametophytes and sporophytes on liverworts look like?

• Most have elevated gametophytes that resemble miniature trees (Marchantia)

• Reduced or very small sporophytes; Some “thalloid” and others “leafy”

What does the sporophyte of hornworts look like? With what organism do they have a symbiotic relationship with?

• Common name refers to horn-like long tapered shape of sporophyte

• Good colonizers of moist soils

• Symbiotic relationship with nitrogen-fixing cyanobacteria

How are mosses different from other nonvascular plants? How does its structure allow for spore dispersal?

• The most numerous of the non-vascular plants

• Inhabit extreme environments as mountain tops, tundra, and deserts

• Sporophyte grows up from female gametophyte to gain elevation for spore dispersal

What is the ecological importance of mosses? Give an example.

• “pioneer” species in nutrient-poor soils

• moss are major primary producers in cold or highaltitude regions

  • Sphagnum “peat moss” bogs: important wetlands, also harvested for fuel

  • some peatlands have preserved corpses for thousands of years

Before vascular tissue evolved, what did all land plants look like?

short, ground cover plants

Describe the sporophytes of seedless vascular plants. How is it different from those in seedless nonvascular plants?

• Branched sporophytes that are independent of gametophyte for nutrition (Seedless nonvascular sporophytes depend on gametophytes for food and water)

• Diploid sporophyte dominates life cycle

Describe the vascular system in seedless vascular plants.

• Transport in Xylem and Phloem (vascular system)

  • Xylem: cells specialized to move water and minerals

  • Phloem: cells specialized to move sugars, amino acids, other organic products

What two evolutions did SVP go through?

• Evolution of true roots

• Evolution of true leaves

What is the one type of seedless vascular plant that has microphylls? What does it look like?

Lycophytes (Small, spine-shaped leaves supported by a single strand of vascular tissue)

Instead of microphylls, what most other vascular plants have? How does it differ from microphylls?

• Megaphyll

  • Leaves with a highly branched vascular system

  • Greater photosynthetic productivity than microphylls

What are Sporophylls? How do they differ in ferns and lycophytes?

• Sporophylls are leaves modified to bear sporangia

• Fern sporophylls look like normal leaves but have sori that generate spores on underside

• Lycophyte sporophylls modified into a cone-like structure called a strobilus

Describe the 4 steps of Homosporous spore production and which types of plants undergo this process.

1. Sporangium on sporophyll

2. Single type of spore

3. Typically a bisexual gametophyte

4. Eggs or Sperm

Most seedless vascular plants undergo this

Describe two types of Heterosporous spore production, the steps of each one, and which types of plants undergo this.

• all seed plants and few seedless vascular plants undergo this

• Type 1: Megasporangium on megasporophyll

  1. Megasporangium on megasporophyll

  2. Megaspore

  3. Female gametophyte

  4. Eggs

• Type 2: Microsporangium on microsporophyll

  1. Microsporangium on microsporophyll

  2. Microspore

  3. Male gametophyte

  4. Sperm

What are Lycophytes? Describe them. Give 3 examples. Which ones are heterosporous and which one are homosporous?

• Club mosses and relatives

• Current species all small (1,200 spp.) - tropical and temperate

• EX: Selaginella apoda, a spike moss, Isoetes gunnii, a quillwort, Diphasiastrum tristachyum, a club moss

  • Spike mosses and quillworts are heterosporous

  • Club mosses are homosporous

What are Pterophytes? Give 3 examples and what phylum they belong to

• a group of vascular plants that reproduce by spores instead of seeds

• Horsetails, whisk ferns, and ferns belong to the phylum Monilophyta

Describe whisk ferns (Psilotum) , its structure, and where photosynthesis occurs in it

• dichotomous branching

• no true leaves or roots

• Homosporous

• Photosynthesis occurs in stem

Describe Horsetails (Equisetum), its structure and where photosynthesis occurs.

• jointed stems with tiny leaves

• Strobili (cone at top)

• Homosporous

• Photosynthesis occurs in stems

Describe ferns, its structure and where it grows

• most widespread & diverse Monilophytes

• homosporous

• large megaphylls

• sori on underside of sporophylls

• mostly in understory or as epiphytes : grows on the surface of a plant

Fill in the blank for the fern life cycle

What is the importance of mosses, ferns, peat moss, and SVPs

• Disappearance of mosses = Biological indicator of environmental pollution

• Ferns

  • Promotes weathering of rocks = Accelerates topsoil formation

  • Used as food

• Peat moss (Sphagnum)

  • Used as fuel (renewable resource)

  • Soil conditioner

• Extinct SVPs

  • Coal = Energy source