Charophyte Green Algae

Question 1

Charophyte Green Algae are?

Answer 1

1. Basal lineages, unicellular

Question 2

What traits do Charophyte algae share with land plants

Answer 2

1. cytokinesis by phragmoplast & cell plate 
    in most
2. Asymmetrical flagellar roost system & 
    multilayered structure
3. Lateral / subapical flagella
4. Rosette configuration of cellulose  
    synthase
5. Several enzyme/enzyme systems
6. Capacity to produce sporopollenin
7. Oogamy

Question 3

Oogamy

Answer 3

Unequal size and motility. Eggs are larger (no motility) and Sperm are small (motile)

Question 4

Isogamy

Answer 4

Equal size of Egg and Sperm

Question 5

Present in most Charophytes, but not all?

Answer 5

1. Plasmodesmata
   
   • microscopic channels enabling
     transport and communication between
     cells
2. Apical growth
   
   • division of single large apical cell
     results in length growth

Question 6

Charophyte: Zygnematales

Answer 6

1. Unicells, filaments, colonies
   
   • extensive mucilage production
2. Among the most common algae in
   freshwater
3. Conjugation
   
   • no motile cells
   • Amoeboid isogametes
   • Conjugation tubes
   • Zygotic meiosis

Question 7

Charophyte: Spirogyra

Answer 7

1. Unbranched filaments
2. Spiral arrangement of ribbon chloroplasts
3. Asexual reproduction by fragmentation
4. Sexual reproduction triggered by adverse environmental conditions (usually in the fall)

Question 8

Charophyte: Desmids

Answer 8

1. One cell in two mirror-images parts
   
   • two halves (semi-cells) connect in the
     center by the narrow constriction, the
     isthmus (nucleus present there).
   • At cytokinesis, desmids separate at
     center and each daughter cell gets half
     of parent wall

Question 9

Charales: Chara?

Answer 9

1. Mostly freshwater
   
   • grows submerged (extensive
     underwater meadows)
2. Stoneworts (calcified cell walls)
3. Apical growth
4. Thallus attached to mud or silt by
   RHIZOIDS

Question 10

Chara Morphology

Answer 10

1. Nodes and Internodes
   
   • internodes composed of one relatively
     long multinucleated cell (parenchyma-
     like)
   • Nodal region are parenchymatous.
     Plasmodesmata connect node cells.
     Whorled branches arise at nodes

Question 11

Chara Reproduction

Answer 11

1. Gametangia (gamete producing
   structure) more complex than in other
   algae
2. Surrounded by vegetative (non-
   reproductive) cells
   * Antheridia
   * Oogonia
3. Zygote released when mother thallus
   decays (zygotic meiosis)

Question 12

Antheridia

Answer 12

1. Spherical
2. Shield cells are orange due to carotene
3. Flagellated sperm

Question 13

Oogonia

Answer 13

1. oblong
2. One egg
3. Tube Cells: helically twist around the
   central egg cell
4. Crown Cells: sit on top of the tube cells

Question 14

Colechaetales: Coleochaete

Answer 14

1. Few species in freshwater
2. Attached to aquatic plants, rocks, or soil
3. Sheathed hairs are assumed to have an
   anti-herbivory function
4. Single chloroplast in each cell
5. Diverse morphology
   
   • filamentous
   • pseudoparenchyma
   • parenchymatous disks
     (cell divison only by outermost cells
     and often in shallow water, where
     frequent exposed to desiccation)

Question 15

Coleochaete orbicularis Reproduction

Answer 15

1. Multicellular antheridia produce sperm
   
   • sperm have no plastids
2. Upright oogonia produce one egg, which
   is retained & fertilized on the thallus
3. Sterile sheath encloses zygote after
   fertilization
   
   • sporopollenin in cell walls of sterile
     sheaths
   • Sterile sheath nourishes zygote via
     cell-wall ingrowths.
4. Zygote divides by meiosis and then by
   mitosis while on the parental thallus
   (mitotic divison = more spores)