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Chapter 17 Notes

by: Min-Young Kim

Chapter 17 Notes BIOL 3040

Marketplace > Clemson University > Biology > BIOL 3040 > Chapter 17 Notes
Min-Young Kim
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These notes cover the entire content of Chapter 17 in the textbook for Dr. Wells' class.
Biology of Plants
Christina Wells
Class Notes
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This 6 page Class Notes was uploaded by Min-Young Kim on Wednesday February 3, 2016. The Class Notes belongs to BIOL 3040 at Clemson University taught by Christina Wells in Spring 2016. Since its upload, it has received 41 views. For similar materials see Biology of Plants in Biology at Clemson University.


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Date Created: 02/03/16
Chapter  17  Notes     -­‐ Vascular  plants:  sporophytes  more  prominent  than  gametophytes  and  are   free-­‐living.     o Xylem  and  phloem  solved  problem  of  food  and  water  transport   throughout  plant  body.     o Ability  to  synthesize  lignin  also  helped  (adds  rigidity  allows   vascularized  sporophytes  to  reach  great  heights)   o Branch  profusely  at  apical  meristems,  produce  multiple  sporangia     -­‐ Ancient  vascular  plants  gave  rise  to  more  specialized  plants  with  highly   differentiated  plant  body   o Roots  (anchorage  and  absorption)   o Stem  and  leaves  (acquisition  of  energy,  carbon  dioxide,  and  water)   o Seeds  (structures  that  provide  embryonic  sporophyte  with  nutrients   and  protect  it  from  rigors  of  life  on  land)   -­‐ Sporophytes  of  early  vascular  plants  were  dichotomously  branched  axes  that   lacked  roots  and  leaves     o Root  system  and  shoot  system  (stems  and  leaves)   -­‐ Dermal  tissue  system:  outer,  protective  covering  of  plant   -­‐ Vascular  tissue  system:  conductive  tissues  (xylem  and  phloem),  embedded   in  ground  tissue  system   -­‐ Primary  growth:  growth  that  occurs  relatively  close  to  the  tips  of  roots  and   stems;  initiated  by  apical  meristems,  involved  with  extension  (usually   vertical)  of  the  plant  body;  (primary  tissues,  primary  plant  body)   -­‐ Secondary  growth:  thickens  stem  and  root.  Results  from  activity  of  lateral   meristems   o Vascular  cambium:  produces  secondary  vascular  tissues   (secondary  xylem  and  phloem)   o Cork  cambium:  forms  periderm,  composed  mainly  of  cork  tissue;   replaces  epidermis  as  dermal  tissue  system  of  plant   o Secondary  vascular  tissues  and  periderm  make  up  secondary  plant   body   -­‐ Tracheary  elements:  conducting  cells  of  xylem;  distinctive  lignified  wall   thickenings     -­‐ Sieve  elements:  conducting  cells  of  phloem,  soft  walls  and  often  collapse  after   death,  don’t  fossilize  well   -­‐ Tracheids:  only  type  of  water-­‐conducting  cell  in  most  vascular  plants;   provide  channels  for  water  and  minerals,  as  well  as  support  for  stems;  rigid   lignin  in  walls   -­‐ Vessel  elements:  principal  water-­‐conducting  cell  in  angiosperms.  Evolved   independently  in  several  groups  of  vascular  plants  (good  example  of   convergent  evolution)   -­‐ Stele:  central  cylinder  in  primary  plant  body  made  up  of  primary  xylem  and   phloem,  as  well  as  pith  (central  column  of  ground  tissue)   o Protostele:  simplest  and  most  ancient;  solid  cylinder  of  vascular   tissue;  phloem  either  surrounds  xylem  or  interspersed  in  it  (in  extinct   seedless  vascular  plants,  lycophytes,  and  most  roots)   o Siphonostele:  in  stems  of  most  seedless  vascular  plants;  central  pith   surrounded  by  vascular  tissue;  phloem  on  outside  of  xylem  or  on  both   sides  of  it  (in  ferns,  leaf  traces  marked  by  leaf  gaps,  called  leaf  trace   gaps)   o Eustele:  primary  vascular  cylinder  consists  of  system  of  discrete   strands  around  pith  (siphonosteles  evolved  independently  from   protosteles.  None  of  the  seedless  vascular  plants  gave  rise  to  any   living  seed  plants)   -­‐ Microphylls:  relatively  small  leaves  that  contain  only  single  strand  of   vascular  tissue;  typically  associated  with  stems  possessing  protosteles  and   characteristic  of  lycophytes   o Leaf  traces  not  associated  with  leaf  gaps,  usually  only  single  vein  in   each  leaf   o May  have  evolved  as  superficial  lateral  outgrowths  of  stem  or  from   sterilization  of  sporangia  in  lycophytes  ancestors   -­‐ Megaphylls:  larger;  associated  with  stems  that  have  either  siphonosteles  or   eusteles   o Leaf  traces  associated  with  leaf  gaps  and  leaf  trace  gaps;  blade  has   complex  system  of  branching  veins   o Unequal  branching  resulted  in  more  aggressive  branches   “overtopping”  weaker  ones   -­‐ All  vascular  plants  oogamous  and  have  alternation  of  heteromorphic   generations   -­‐ Homosporous:  early  vascular  plants  produced  only  one  kind  of  spore  as  a   result  of  meiosis   o Found  in  most  ferns,  horsetails,  and  some  lycophytes   o Condition  from  which  heterospory  evolved   o Homosporous  plants  have  potential  to  produce  bisexual   gametophytes,  but  most  fern  sporophytes  are  heterozygous   -­‐ Fern  mechanism  for  cross-­‐fertilization:  maturation  at  different  times  for   antheridia  and  archegonia.  Sperm  produced  by  one  gametophyte  fertilize   eggs  of  neighboring   o Sex  expression  determined  by  age  of  plant  of  water-­‐soluble   substances  called  antheridiogens.  Self-­‐fertilization  does  occur   -­‐ Heterospory:  production  of  two  types  of  spores  in  two  different  kinds  of   sporangia     o Found  in  some  lycophytes,  few  ferns  and  all  seed  plants   o Microspores  and  megaspores  produced  in  microsporangia  and   megasporangia;  differentiated  based  on  function  and  not  necessarily   size.  Microspores  à  male  gametophytes.  Megaspores  à  female   gametophytes.   o Heterosporous  plants  –  gametophytes  form  within  the  spore  wall   (endosporic).  Homosporous  plants  –  gametophytes  develop  outside   spore  wall  (exosporic  development)   -­‐ Relatively  large  gametophytes  of  Homosporous  plants  are  independent  of   sporophyte  for  nutrition.  Gametophytes  of  many  Heterosporous  vascular   plants,  especially  seed  plants,  are  dependent  on  sporophyte  for  nutrition   -­‐ Within  vascular  plants,  evolution  of  gametophytes  is  characterized  by  overall   trend  toward  reduction  in  size  and  complexity   -­‐ In  angiosperms  and  in  most  gymnosperms,  entire  microgametophytes   (pollen  grains)  are  carried  to  vicinity  of  megagametophyte.  Transfer  of   pollen  grains  is  pollination.  Germination  of  pollen  grains  produces  special   structures  called  pollen  tubes,  through  which  motile  sperm  swim  to  the  egg   to  achieve  fertilization   -­‐ Overall  pattern  of  diversification  of  plants:   1. Early  vascular  plants,  characterized  by  relatively  small  stature  and   simple  presumable  primitive  morphology  (rhyniophytes,   zosterophyllophytes,  trimerophytes)  425-­‐370  mya   2. Monilophytes,  lycophytes,  and  progymnosperms.  375-­‐290  mya   3. Seed  plants;  380  mya   4. Flowering  plants;  135  mya   -­‐ Rhyniophyta:  seedless  plants,  consisting  of  dichotomously  branching  axes   with  terminal  sporangia     o Rhynia  Gwynne-­‐vaughanii.  Marsh  plant,  numerous  lateral  branches   and  short  branches  on  which  sporangia  often  borne;  single  layer  of   superficial  cells  (epidermis)  surrounded  by  photosynthetic  tissue  of   cortex;  center  of  axis  consisting  of  xylem  and  phloem-­‐like  cells   o Aglaphyton  major:  extensive  dichotomously  branched  rhizome   system;  protracheophytes  (intermediate  stage  in  vascular  plants);   ells  more  like  hydroids  of  modern  mosses  than  tracheids   o Cooksonia:  rhyniophyte  inhabited  mud  flats;  oldest  known  vascular   plant;  slender  leafless  aerial  stems;  long  and  terminated  in  globose   sporangia;  tracheids  identified   -­‐ Zosterophyllophyta:  leafless  and  dichotomously  branched;  aerial  stems   covered  with  cuticle,  only  upper  ones  contained  stomata;  lower  branches   produced  lateral  branches  forking  into  two  axes;  sporangia  borne  laterally  on   short  stalks;  homosporous;  centripetal  differentiation;  ancestors  of   lycophytes   -­‐ Trimerophytophyta:  evolved  from  rhyniophytes;  diverse  evolutionary   relationships  and  ancestral  stock  of  both  ferns  and  progymnosperms;  larger   and  more  complex;  relatively  short  period  of  existence;  lacked  leaves  but  had   complex  branching;  more  massive  vascular  strand   -­‐ Lycopodiophyta:  representatives  of  evolutionary  line  extending  back  to   Devonian  period;  basal  split  separated  lycophyte  clade  (modern  lycophyte   lineage)  and  euphyllophyte  clade  (monilophytes  and  seed  plants);  non-­‐ woody  herbaceous  plants;  possess  Microphylls   o Lycopodiaceae  (club  mosses):  sporophytes  consist  of  branching   rhizome  from  which  aerial  branches  and  roots  arise;  both  stems  and   roots  protostelic;  Microphylls  usually  spirally  arranged;   homosporous;  sporangia  on  sporophylls;  strobili:  cones  at  ends  of   branches   § Upon  germination,  spores  give  rise  to  bisexual  gametophytes   that  are  either  green  irregularly  lobed  masses  or  subterranean   non-­‐photosynthetic  mycorrhizal  structures   § Gametophytes  predominantly  cross-­‐fertilize;  self-­‐fertilization   rates  low   § Water  required  for  fertilization.  Biflagellated  sperm  à   archegonium  àfertilization  àzygote  àembryo  àyoung   sporophyte  remains  attached  to  gametophyte,  but  eventually   becomes  independent   o Selaginella  (spike  mosses):  resurrection  plant;  bears  Microphylls  and   sporophylls  arranged  in  strobili;  small  scale-­‐like  outgrowth  (ligule)   near  base  of  upper  surface  of  each  microphyll  and  sporophyll;  stem   and  root  protostelic   § Heterosporous:  unisexual  gametophytes.  Each  sporophyll   bears  single  sporangium  on  upper  surface.  Megasporangia   borne  by  megasporophylls,  and  microsporangia  borne  by   microsporophylls;  both  occur  in  same  strobilus   § Microgametophytes  develop  within  microspore,  lack   chlorophyll;  microspore  wall  must  rupture  for  sperm  to  be  free   § Megaspore  wall  ruptures  and  gametophyte  protrudes  through   rupture  to  outside  (megagametophyte)     § Water  required  for  fertilization;  occurs  after  gametophytes   shed  from  strobilus   § During  development  of  embryos  in  both  Lycopodiaceae  and   Selaginella,  suspensor  formed:  serves  to  thrust  developing   embryo  deep  within  nutrient-­‐rich  tissue  of  female   gametophyte;  developing  sporophyte  emerges  from   gametophyte  and  becomes  independent   o Iosetes  (quillworts):  nearest  living  relative  of  ancient  tree  lycophytes   of  Carboniferous.  Sporophyte  has  short  fleshy  underground  stem   (corm)  bearing  quill-­‐like  microphylls  on  upper  surface  and  roots  on   lower  surface   § Heterosporous:  megasporangia  borne  on  megasporophylls;   microsporangia  borne  on  microsporophylls   § Specialized  cambium  adds  secondary  tissues  to  corm;  only   parenchyma  tissue  externally,  but  internal  tissue  of  sieve   elements,  parenchyma  cells,  and  tracheids   § Leaves  of  plants  lack  stomata;  have  thick  cuticle;  no  gas   exchange;  CAM  photosynthesis   -­‐ Monilophyta:  ferns  and  horsetails;  ferns  are  largest  and  most  diverse  group   of  plants  other  than  angiosperms;  third  of  all  tropical  ferns  grow  on  trunks  or   branches  as  epiphytes;  most  homosporous   o Lygodium:  climbing  fern;  leaves  with  long  twining  rachis;  tissues   primarily  at  origin;  thickness  is  fibrous  root  mantle   o Eusporangium:  parent  cells  located  at  surface  of  tissue  from  which   sporangium  produced;  inner  and  outer  series  of  cells;  inner  layer   gives  rise  to  irregularly  oriented  cells  from  which  spore  mother  cells   ultimately  arise   § Psilopsida  and  Marattiopsida:  single  leaf  produced  each  year   from  stem:  1)  vegetative  portion  2)  fertile  segment   • Sporophyte  of  Psilotum  has  dichotomously  branching   aerial  portion  and  underground  branching  portion  of   rhizomes  and  rhizoids;  generally  aggregated  on  ends  of   short  lateral  branches   • Tmesipteris:  grows  as  epiphyte  on  tree  ferns  and  rocks   • Marattiopsida:  ancient  group  resembling  ferns   § Equisetopsida:  single  homosporous  herbaceous  genus;   horsetails;  internodes  ribbed;  roots  at  nodes  of  rhizomes;   carinal  canals  associated  with  xylem  and  phloem;   sporangiophores  (sporangia-­‐bearing  branches  clustered  into   strobili);  sporangia  contract  and  split  along  inner  surface,   releasing  numerous  spores;  elaters  (thickened  bands)  coil   when  moist  and  uncoil  when  dry;  green  and  free-­‐living   gametophytes  (in  bisexuals,  archegonia  develop  before   antheridia)     o Leptosporangia:  arise  from  single  superficial  initial  cell;  divides   transversely  or  obliquely;  cells  either  produce  large  part  of  sporangial   stalk  or  remain  inactive;  outer  cell  gives  rise  to  elaborate  stalked   sporangium,  with  a  spherical  capsule  (two-­‐layered  tapetum);  inner   mass  divides  into  spore  mother  cells   § Tapetum  nourishes  cells;  material  from  tapetum  deposited   around  spores;  spores  exposed  to  lip  cells  of  sporangium;   sporangia  stalked,  containing  annulus;  sporangium  dries;   annulus  tears  middle  of  capsule;  explosion  and  snap  back;   catapult-­‐like  discharge  of  spores   § Polypodiopsida:  homosporous;  nearly  all  ferns;  siphonostelic   rhizomes  produce  new  sets  of  leaves  each  year;  fronds  are   megaphylls,  high  surface-­‐to-­‐volume  ratio  allows  effective   capture  of  sunlight;  lamina  divided  into  pinnae,  attached  to   rachis;  circinate  vernation;  sporangia  commonly  occur  in   clusters  called  sori;  young  sori  covered  by  indusia;     • Gametophyte  develops  into  prothallus  (flat,  heart-­‐ shaped,  numerous  rhizoids  on  lower  surface)   • Archegonia  and  antheridia  develop  on  ventral  surface  of   prothallus;  timing  of  maturation  of  antheridia  and   archegonia  can  determine  self-­‐fertilization  or  cross-­‐ fertilization   • Embryo  (young  sporophyte)  receives  nutrients  through   foot;  develops;  independent  plant;  gametophyte   disintegrates  (exceptions)   § Salviniales:  heterosporous;     • Marsilea:  leaves  resemble  four-­‐leaf  clover;  grow  in  mud   or  on  surface  of  water;  sporocarps:  drought-­‐resistant   bean-­‐shaped  reproductive  structures   • Azolla  and  Salvinia:  plants  on  surface  of  water;  Azolla   has  bi-­‐lobed  leaves  with  pouches  of  cyanobacteria;   Salvinia  has  undivided  leaves  “roots”  hanging  down,   bear  sporangia  


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