monilophytes

Question 1

what are euphyllophytes? what are their origins?

Answer 1

• clade containing monilophytes, gymnosperms and anthrophyta
• Multiple vascular strands in each leaf (lycophytes are microphylls)
• Functional ecological difference is not great but shows different evolutionary origins
• Probably evolved from leafless ancestors (ancestor of euphylls and lycopods)
• Two separate origins of euphylls in euphyllophytes

Question 2

the evolution of euphylls in trimerophyta

Answer 2

• 405-375 mya
• Larger plants that rhyniophytes with more complex dichotomous branching
• No leaves, but enations in some species; rhizomes but not roots
• Clusters of sporangia at tips of fertile branches

Question 3

features of leptosporangiate ferns

Answer 3

• Circinate leaf development (curled young leaf)
• Leaves: Peritole is the stem and lamina is the blade of the leaf and rachis is the centre of the lamina
• Lamina can be pinnate form or bipinnate form
• Ground level rhizomes but also have true roots

Question 4

where are the sporangia located in leptosporangiate ferns? How do they release spores?

Answer 4

• Cluster of sporangia on underside or margins of leaves
• Clustered in sorus (sori)
• Leptosporangium means that the sporangia are on a short stalk
• Spores are surrounded with an annulus (thickened cell walls on three sides)
• When spores develop, the annulus dries out and shrinks causing it to contract and rip open the spore sac and the spores are thrown out

Question 5

what happens when the spores land on the ground?

Answer 5

• Spores land on the ground and grow a haploid gametophyte with two thaloid lobes (small but photosynthetic)
• Gametangia are formed (antheridia and archegonia)
• Sperm are not dispersed at the same time that the eggs are receptive
• Larger gametophytes (just produce eggs) send out signals to smaller gametophytes telling them just to produce sperm (they can be bisexual but often are not)

Question 7

what are the two families of leptosporangiate ferns?

Answer 7

• Marsileaceae (rooted water ferns)
• Salviniaceae (floating water ferns)
• Independent evolution of heterospory in these groups

Question 8

describe marattiaceae

Answer 8

• Tropical and subtropical, often in montane forests
• Leaves large and 1- to 3- pinnate
• Commonly with large fleshy rhizome
• Gametophytes flat, surface-dwelling, photosynthetic, up to 2cm long
• Eggs and sperm are produced and fuse, growing a sporophyte

Question 9

describe Orphioglossaceae

Answer 9

• Leaves divided into basal vegetative part and sporangium-bearing upper segment (may have derived from dichotomous branching)
• Homosporous
• Subterranean gametophyte with symbiotic fungus

Question 10

describe Psilotum:

Answer 10

• Simplified seeming primitive traits like rhinophyltes
• Dichotomous branching; lacks leaves but has enations
• Simple vascular strand in stem (protostele)
• Lacks roots but has rhizomes with rhizoids and endomycorrhizae fungus
• Non-photosynthetic gametophyte with symbiotic fungus

Question 11

describe Equisitaceae:

Answer 11

• Usually in locally damp sites such as river banks
• Whorled branches and scale-like leaves at nodes
• Distinctive stem anatomy: hollow, ribbed stem with siliceous deposits
• Distinctive strobilus with sporangia set on short stalks (sporangiophores)
• Green, free-living gametophytes (1-3cm)