Seedless  vascular  plants  

Seedless vascular plants

Reduction of the gametophyte Monophyletic linage

Seedless vascular plants

•  Phyla or Divisions of seedless vascular plants

–  Rhyniophyte (extinct) –  Zosterophyllophyte (extinct) –  Trimerophyphyte (extinct) –  Lycopodiophyta –  Pteridophyta

Running-­‐cedar  or  Fan  Ground-­‐pine  

ferns  

Organization of the seedless vascular plant body

–  Root and shoot systems –  Dermal tissue system

•  dermal •  vascular •  ground

–  Vascular tissue system •  xylem •  Phloem

–  Ground tissue system

–  Primary growth –  Secondary growth

Evolu1on  of  the  vascular  system  • Tracheids (primitive conduction) • Vessel elements (convergent evolution)

or  stele  

Protostele: (Primitive) solid cylinder of vascular tissue. Siphonostele: Most common in seedless vascular plants. Central pith surrounded by vascular tissue Eustele: Organized with vascular bundles. Independent evolution from protostele

Microphylls:  with  single  strand  of  vascular  ;ssue.  Originated  as  ena;ons.    Megaphylls:  with  branching  veins,  associated  with  siphonosteles,  leaf  gaps  and  eusteles.  Originated  by  fusion  of  branch  systems.  

Reproduction

All vascular plants •  Oogamous •  Alternation of heteromorphic generations

(sporophyte dominant) •  Homosporous or heterosporous

–  Homosporous Produce bisexual gametophytes

•  (A) Antheridia •  (B) Archegonia •  Not self fertilized

Reproduction –  Heterosporous

•  megaspores produced in megasporangia

= ♀ gametophyte (a.k.a. megagametophyte)

•  microspores produced in microsporangia

= ♂ gametophyte (a.k.a. microgametophyte)

•  Unisexual gametophytes

•  Gametophytes of homosporous plants –  photosynthetic

•  Gametophytes of heterosporous plants –  dependent of sporophyte

Extinct groups •  Leafless •  Dichotomously branched •  Stems with terminal sporangia •  Vascular tissue similar to hydroids in mosses •  Homosporous •  Cuticle, epidermis, cortex, stomata and

photosynthetic stems •  Isomorphic generations •  Marshes

dichotomously  branched  

Minimal  differen;a;on  of  roots/stems  

Phylum / Division Rhyniophyta ���

 

Zosterophyllophyta •  370-408 MYA •  Laterally borne kidney-

shaped sporangia •  Grass-like appearance •  Ancestor of lycophytes

Phylum / Division Zosterophyllophyta and

Trimerophyta

Trimerophyta •  395-415 MYA •  Evolved from Rhyniophyta •  Large vascular strand •  Ancestor of pteridophytes and

progymnosperms

•  1200 sp. •  Trees or herbs with secondary growth •  All of them possess microphylls •  400 MYA divergence from

–  lycophytes – club mosses •  tree lycophytes dominant in

Carboniferous –  Euphyllophytes – ferns,

horsetails, seed plants

Phylum Lycopodiophyta

Spores  with  high  oil  content.  

•  15 genera, 1200 sp. •  Club moss (Lycopodium sp.) •  Arctic to tropics, evergreen •  Rhizome with roots and stems •  Spiral microphylls •  Sporangia on sporophyll •  Homosporous •  Some sporophylls non-photosynthetic •  Bisexual gametes •  Cross-fertilize

–  6 - 15 yrs for mature archegonia/antheridia

•  Biflagellate sperm •  Independent sporophyte

Family Lycopodiaceae

strobili Cone-like

•  1 genus, 750 sp. •  Tropics to deserts

•  Selaginella – resurrection plant

•  Ligule = small, scale-like outgrowth at the base of sporophylls

Family Selaginellaceae

Trabeculae  

Protostele  

•  Heterosporous

–  Megasporangia –  Microsporangia contained on single strobili

•  Biflagellate sperm

•  Suspensor connection between the embryo and the nutrient-rich tissue in the female gametophyte •  Sporophyte parasite of gametophyte

Family Selaginellaceae

•  1 genus Isoetes (quillwort)

•  Sporophyte body –  underground stem and roots –  microphllys

•  Heterosporous

•  Cambium produces 2º tissues ü  sieve elements ü  tracheids ü  parenchyma

•  Sediment as source of Carbon from sediment –  Lack stomata –  Thick cuticle, –  Minimal gas exchange with atmosphere –  CAM

Family Isotaceae

Phylum Pterophyta

•  11,000 sp. •  Some epiphytic •  Now includes Sphenophyta

(horsetails)

•  Homosporous or heterosporous

•  2 types of sporangia –  eusporangia = multiple initials or parent cells

•  inner layer = irregular mass, gives rise to spore mother cell •  outer layer = sporangium wall

Phylum Pterophyta

–  leptosporangia = one superficial initial •  stalked sporangium •  capsule with nutritive tissue (tapetum) •  tapetum è annulus that contracts to catapult spores •  inner tissue becomes spore mother cells

Phylum Pterophyta

Phylum Pterophyta. Equisetales

One genus: Equisetum (horsetails) Homosporus Spores with elaters

• Photosynthetic shoot

• Nodes and internodes Perennial rhizomes

• Shoot with terminal strobilus.

• Whorls of scale-like leaves

• Low content of chlorophylls or no chlorophylls