Lecture 4: Streptophyta Flashcards
What is the representative of the earliest diverging land plants lineage?
bryophytes
- green land plants with gametophyte-dominated life cycle, bearing unbranched sporangia (sporophyte ephemeral, trophically dependent on gametophyte)
- gametophyte mostly consisting of 2 distinct phases – protonema and gametophore
What land plant lineage only has prevailing autotrophic gametophyte in their life cycle?
embryophytes
What is gametophyte?
life stage producing gametes (haploid, n)
Where are gametes produced?
in gametangia
- antheridia (♂) – motile sperm cells,
- archegonia (♀) – sessile egg cell
What is sporophyte?
life stage producing meiotic spores (diploid, 2n) following the meitotic division of spore mother cells (2n)
Does sporophyte depend pn gametophyte?
Yes, depends on it trophically
What are salient characteristics of liveworts
liverworts: <10,000 spp.,
- probably the oldest group (Silurian?);
- thallose or foliose gametophore
- protonema reduced, 1 gametophore from a spore
- thallose forms simply built (homogeneous) or complex (tissue differentiation); water conducting cells (hydroids) rare, with perforated ends
- foliose forms mostly with 3-ranked foliage, leaves often lobed
- oil bodies present in gametophytic cells
sporophyte ephemeral, composed of hyaline seta and simple sphaerical or ellipsoid sporangium which opens by rupturing
- sterile elaters among spores, no stomata in sporangial wall, synchronous spore maturing; hygroscopic elaters serving dispersal of spores
WHat are main characteristics of bryophyta and what are the main lineages?
- growth via individual meristematic (apical) cells, not meristematic tissues (meristems)
- absence of lignin in cell walls (→ reduced size, poor fossilization)
- 3 main lineages (probably paraphyletic): liverworts (Marchantiophyta), mosses (Bryophyta) and hornworts (Anthocerotophyta)
What are the salient characteristics of mosses
- gametophore always foliose (i.e., stem + leaves) protonema well-developed, branched, multiple buds multiple gametophores from 1 spore
- gametophore growth form erect ( sporophytes on top of stems –acrocarpous), or prostrate, often branched (sporophytes emerging on short side branches –pleurocarpous)
- gametophore common development of water-conducting cells (hydroids), rarely also assimilate-conducting cells (leptoids) (Polytrichales) in contrast to tracheids of vascular plants, no particular thickenings of cell walls, no lignin
- leaves not lobed but commonly multistratose at midrib (costa)
- leaf cells isodiametric or elongate, no oil bodies present
- stomata in the sporangium wall, sterile central cylinder – columella, no elaters
What are characteristics of hornworts
- gametophore similar to thallose liverworts – rosette- or ribbon-like
gametophor: - reduced protonema
- no differentiation of thalli except for mucilaginous cavities
invaded by symbiotic Nostoc-cyanobacteria - antheridia endogeneous, spermatozoids bilaterally symmetrical
sporophyte: - horn-like, without seta
- longitudinal symmetry resulting from the first zygotic division (PPT 3; 33)
- multi-layered wall with stomata
- both columella and elater-like cells (pseudoelaters) present
- continuous growth of the sporophyte by means of intercalary meristeme
- continuous spore maturation and release
How are polysporangiophytes characterized?
- has a structure of branching stems (axes) terminating in sporangia (vascular tissue may or may not be present; however, extant plants are (primarily) vascular)
- prevalence of sporophyte in their life cycle
Do Protracheophytes have vascular tissues?
no, they still have no true vascular tissues
- water-conducting cells without cell wall thickenings
What species of were the earliest Paleozoic polysporangiophytes?
Paratracheophytes and Protracheophytes
What species of Paratracheophytes have true vascular tissues?
Rhyniophytes and Cooksonia
What do true vasular tissues consist of?
xylem and pholem
