Chapter 27
Chapter 27
SEED PLANTS
SEED PLANTS
SEED
SEED SPORESPORE
1
1.. MMuullttiicceelllluullaar r eemmbbrryyoo SSiinngglle e cceellll 2
2.. FFooood d ssuupppplliieed d bby y ttiissssuuee FFooood d oonnlly y iin n tthhe e cceellll 3
3.. MMuullttiicceelllluullaar r sseeeed d ccooaatt CCoovveerriinng g nnoot t cceelllluullaar r 4
4.. DDiippllooiid d ssppoorroopphhyyttee aappllooiid d cceellll !
!.. ""rroodduucct t oo# # ##eerrttiillii$$aattiioonn ""rroodduucct t oo# # mmeeiioossiiss
%here are t&o groups o# seed producing plants'
%here are t&o groups o# seed producing plants' gymnospermsgymnosperms and and angiospermsangiosperms..
•
• "roduce seeds."roduce seeds. •
• (ascular tissue) xylem(ascular tissue) xylem #or &ater and mineral transport and #or &ater and mineral transport and phloemphloem #or dissolved #or dissolved
sugars. sugars.
•
• *ametophyte is very reduced and totally dependent on the sporophyte.*ametophyte is very reduced and totally dependent on the sporophyte. •
• eterosporous) microspores and megaspores.eterosporous) microspores and megaspores.
GYMNOSPERMS GYMNOSPERMS
%here are about 72+ species #ound in all terrestrial habitats grouped into #our divisions ,phyla-. %here are about 72+ species #ound in all terrestrial habitats grouped into #our divisions ,phyla-. %hey have great economic importance) lumber' paper' chemicals.
%hey have great economic importance) lumber' paper' chemicals. I. CARACTERISTICS O! GYMNOSPERMS
I. CARACTERISTICS O! GYMNOSPERMS 1.
1. ooodody y tretrees es anand d shshrubrubs.s. 2.
2. /y/ylem lem madmade oe o# t# tracracheheidsids.. 3.
3. SeeSeeds ads are bre borneorne' e0' e0posposed' ed' in cin coneones ,mes ,megasgastrobtrobilusilus-.-. 4.
4. "oll"ollinatinated bed by &y &ind' ind' seldseldom bom by iny insectsects.s. !.
!. SinSinglgle #erte #ertiliili$at$atioion) spn) sperm eerm egggg embryo. embryo.
II. CONIPEROPYTA
II. CONIPEROPYTA or coni#ers or coni#ers %here are about !!+ species o# coni#ers. %here are about !!+ species o# coni#ers. Many coni#ers produce
Many coni#ers produce resin$resin$ a comple0 mi0ture o# organic compounds that protect the plant a comple0 mi0ture o# organic compounds that protect the plant #rom insect and #ungal attac.
#rom insect and #ungal attac.
•
• esin is stored in resin ducts in the roots' stem' leaves and cones'esin is stored in resin ducts in the roots' stem' leaves and cones'
Cone bearing gymnosperms' e. g. pines' #irs' cypresses' etc. Cone bearing gymnosperms' e. g. pines' #irs' cypresses' etc. 5eaves are needles or scale6lie' rarely broad
5eaves are needles or scale6lie' rarely broad %ena&ion%ena&ion is parallel and open. is parallel and open. 8
8 male cone male cone is calledis called mi"ros&ro'il#smi"ros&ro'il#s' and contains the' and contains the mi"rosporangiami"rosporangia that produce that produce mi"rospores
mi"rospores through meiosis that &ill develop into through meiosis that &ill develop into mi"rogame&ophy&esmi"rogame&ophy&es ,pollen grains-. ,pollen grains-. %he #emale cone is called the
%he #emale cone is called the megas&ro'il#smegas&ro'il#s' &hich produce' &hich produce megasporangiamegasporangia in each o# &hich in each o# &hich a
a megasporemegaspore is produced through meiosis and &ill develop one is produced through meiosis and &ill develop one megagame&ophy&emegagame&ophy&e. 8n egg. 8n egg &ill #orm &ithin the
&ill #orm &ithin the megagame&ophy&emegagame&ophy&e .. "ollination is by &ind.
"ollination is by &ind. No&e(
No&e( Study the life cycle of pine and learn the terminology. Pages 572 - 574.Study the life cycle of pine and learn the terminology. Pages 572 - 574.
III. CYCADOPYTA
III. CYCADOPYTA or cycads or cycads
9mportant in the %riassic ,24:6213 m .y. a-' &hich is called sometimes the 8ge o# Cycads . 9mportant in the %riassic ,24:6213 m .y. a-' &hich is called sometimes the 8ge o# Cycads . Most species are e0tinct. %here are about 14+ living species in tropical and subtropical parts o# Most species are e0tinct. %here are about 14+ living species in tropical and subtropical parts o# the &orld.
the &orld. Cy"a)s
Cy"a)s are palm or #ern6lie plants &ith compound leaves and simple seed cones. are palm or #ern6lie plants &ith compound leaves and simple seed cones. %he are
%he are )ioe"io#s)ioe"io#s) plants are either male or #emale.) plants are either male or #emale.
%hey have a very large motile sperm &ithin the pollen grain but do not need &ater #or pollen %hey have a very large motile sperm &ithin the pollen grain but do not need &ater #or pollen transport.
transport.
"ollination is by air and in some cases by ants. "ollination is by air and in some cases by ants.
I*. GIN+GOPYTA
I*. GIN+GOPYTA or gingoes or gingoes
%here is a single species o# gingo alive today. 9t is native to China &here it has been under %here is a single species o# gingo alive today. 9t is native to China &here it has been under cultivation #or centuries. 9t has been #ound in the &ild in only t&o locations.
cultivation #or centuries. 9t has been #ound in the &ild in only t&o locations. *ingoes are dioecious and have #lagellated sperms.
*ingoes are dioecious and have #lagellated sperms.
"ollination is by air and seeds are borne e0posed rather than in cones. "ollination is by air and seeds are borne e0posed rather than in cones.
9t is commonly planted in 8merican cities because it is very resistant to pollution. 9t is commonly planted in 8merican cities because it is very resistant to pollution.
*. GNETOPYTA *. GNETOPYTA
%he gnetophytes consists o# three genera and about 7+ species. %he gnetophytes consists o# three genera and about 7+ species. 8
8 group o# group o# rare planrare plants that shats that share some trare some traits &ith aits &ith angiospermngiosperms.s.
•
• ;##icient &ater conducting cells in the 0ylem called vessel elements.;##icient &ater conducting cells in the 0ylem called vessel elements. •
• eproductive structures resemble #lo&ers.eproductive structures resemble #lo&ers.
ANGIOSPERMS ANGIOSPERMS
%here are about 23!'+++ species o# #lo&ering plants. %here are about 23!'+++ species o# #lo&ering plants.
%his is the dominant group in terrestrial habitats. <ur survival depends on them. %his is the dominant group in terrestrial habitats. <ur survival depends on them.
•
• #ood' medicine' lumber' etc.#ood' medicine' lumber' etc.
%here are t&o groups o# angiosperms)
%here are t&o groups o# angiosperms) mono"o&smono"o&s and and )i"o&s)i"o&s.. First appeared in the Cretaceous about 13+ million years ago. First appeared in the Cretaceous about 13+ million years ago. I. CARACTERISTICS
I. CARACTERISTICS 1.
1. ooodody or hy or hererbabaceceouous.s. 2.
2. /yle/ylem elemem elements hants have vesve vessel elsel elemenements and tts and trachracheidseids.. 3.
3. "r"rododucuce e #l#lo&o&erers.s. 4.
4. "o"ollillinanated ted by &by &ind oind or anr animaimals.ls. !.
!. DouDoublble #erte #ertiliili$a$atiotion) egn) egg sperg spermm embryo and embryo and 2 2 polar polar nuclei nuclei spermsperm endosperm. endosperm. .
. SeSeededs ens encloclosed sed in a in a #ru#ruit.it.
M<=<C<%S have #loral parts in multiples o# three and the seed contains one cotyledon. %he M<=<C<%S have #loral parts in multiples o# three and the seed contains one cotyledon. %he endosperm provides the #ood #or the embryo. (enation is usually parallel ,there are e0ceptions-. endosperm provides the #ood #or the embryo. (enation is usually parallel ,there are e0ceptions-. %heir vascular bundles are scattered throughout the ground tissue. %he root system is #ibrous. %heir vascular bundles are scattered throughout the ground tissue. %he root system is #ibrous. D9C<%S have #loral parts in multiples o# #our or #ive' and their seeds contain t&o cotyledons. D9C<%S have #loral parts in multiples o# #our or #ive' and their seeds contain t&o cotyledons. %he cotyledons usually absorb the #ood #rom the endosperm #irst' and then provide the #ood #or %he cotyledons usually absorb the #ood #rom the endosperm #irst' and then provide the #ood #or the embryo. (enation is netted. %he vascular bundles in the stem cross6section are arranged in the embryo. (enation is netted. %he vascular bundles in the stem cross6section are arranged in circles ,rings-. %hey usually have a taproot system #or at leas part o# their li#e.
circles ,rings-. %hey usually have a taproot system #or at leas part o# their li#e.
II. TE !LO,ER II. TE !LO,ER
%he #lo&er is a reproductive shoot or branch. %he #lo&er is a reproductive shoot or branch.
9t has #our parts arranged in &horls or circles on a stal or peduncle. 9t has #our parts arranged in &horls or circles on a stal or peduncle.
%he parts o# the #lo&er are the
%he parts o# the #lo&er are the sepalssepals ,caly0-' ,caly0-' pe&alspe&als ,corolla-' ,corolla-' s&amenss&amens and and "arpels"arpels..
•
• Stamens consist o# a #ilament and an anther.Stamens consist o# a #ilament and an anther. •
• Carpels are also re#erred to asCarpels are also re#erred to as pis&ilspis&ils. %hey consist o# an ovary' a style and a. %hey consist o# an ovary' a style and a
stigma. stigma.
Flo&ers may be borne singly or in clusters called
Flo&ers may be borne singly or in clusters called in-lores"en"ein-lores"en"e.. Flo&er parts are considered modi#ied leaves.
Flo&er parts are considered modi#ied leaves. Flo&ers may be ...
Flo&ers may be ...
•
• Comple&e i# has the #our parts orComple&e i# has the #our parts or in"omple&ein"omple&e i# it lacs one o# the parts. i# it lacs one o# the parts. •
• Per-e"& i# it has both stamens and carpels orPer-e"& i# it has both stamens and carpels or imper-e"&imper-e"& i# it lacs one o# them. i# it lacs one o# them.
See figure 27-10, page 579, for additional details of the floral structure See figure 27-10, page 579, for additional details of the floral structure ..
III. DO/LE !ERTILI0ATION III. DO/LE !ERTILI0ATION..
9t is characteristic o# #lo&ering plants. 9t is characteristic o# #lo&ering plants.
Double #ertili$ation results in the #ormation o# a
Double #ertili$ation results in the #ormation o# a )iploi) 1ygo&e)iploi) 1ygo&e and a and a &riploi) en)osperm&riploi) en)osperm.. %he #emale
%he #emale game&ophy&e or em'ryo sa"game&ophy&e or em'ryo sa" has an egg nucleus and t&o polar nuclei. has an egg nucleus and t&o polar nuclei. <ne sperm #ertili$es the egg nucleus and #orms the $ygote' 2n.
<ne sperm #ertili$es the egg nucleus and #orms the $ygote' 2n. 8nothe
8nother sperm >oins r sperm >oins the t&o pthe t&o polar nucleolar nuclei #orming thi #orming the triploid ,3e triploid ,3n- nutritive n- nutritive tissue caltissue called theled the endosperm.
endosperm.
See figure 27-12, page 51, for details. See figure 27-12, page 51, for details.
Seeds develop #rom the ovule #ollo&ing #ertili$ation. Seeds develop #rom the ovule #ollo&ing #ertili$ation. %he ovary enlarges and #orms the #ruit.
%he ovary enlarges and #orms the #ruit.
9n some instances other tissues also enlarge and become part o# the #ruit. 9n some instances other tissues also enlarge and become part o# the #ruit. Fruits serve t&o purposes) protect the seed and aid in dispersal o# the seeds. Fruits serve t&o purposes) protect the seed and aid in dispersal o# the seeds.
E*OLTION O! SEED PLANTS E*OLTION O! SEED PLANTS
"rogymnosperms appeared about 37! million years ago in the Devonian. "rogymnosperms appeared about 37! million years ago in the Devonian.
•
• they reproduced by spores.they reproduced by spores. •
• had megaphylls.had megaphylls. •
%heir reproductive structures appear to be intermediate bet&een those o# spore producing %heir reproductive structures appear to be intermediate bet&een those o# spore producing plants and seed plants.
plants and seed plants.
coni#ers coni#ers "rogymnosperms
"rogymnosperms
seed #erns seed #erns cycads and possibly gingoes cycads and possibly gingoes Seed producing plants appeared in the Devonian' about 3+ m. y. a.
Seed producing plants appeared in the Devonian' about 3+ m. y. a.
?y the end o# @urassic' 1:+ million years ago' several lines o# gymnosperms e0isted &ith ?y the end o# @urassic' 1:+ million years ago' several lines o# gymnosperms e0isted &ith #eatures that resembled those o# #lo&ering plants.
#eatures that resembled those o# #lo&ering plants.
Di##erent groups o# seed plants apparently appeared independently several times. Di##erent groups o# seed plants apparently appeared independently several times. 8ngiosp
8ngiosperms probaberms probably arose #roly arose #rom ancient m ancient gymnospgymnosperms. %hey erms. %hey must have must have been dbeen dicots' &hiicots' &hichch then gave rise to monocots.
then gave rise to monocots.
%he oldest #ossil record o# angiosperms is pollen #rom the Cretaceous' about 13+ m. y. a. %he oldest #ossil record o# angiosperms is pollen #rom the Cretaceous' about 13+ m. y. a. %he oldest #lo&er #ossil is 12+ m.y.a.
%he oldest #lo&er #ossil is 12+ m.y.a.
?y late Cretaceous angiosperms had began to replace gymnosperms as the dominant group o# ?y late Cretaceous angiosperms had began to replace gymnosperms as the dominant group o# land plants.
land plants.
Many angiosperm species apparently arose #rom changes in chromosome number. Many angiosperm species apparently arose #rom changes in chromosome number.
COMPA
COMPARISON RISON O! GYMNOSPERMS O! GYMNOSPERMS AND ANGIOSPERMSAND ANGIOSPERMS.. *
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