Download Kingdom Plants chapter 29-30

Kingdom Plants chapter 29-30
Multicellular – formed of many specialized cells
Autotrophic – make food by photosynthesis
Eukaryote – formed of one or many eukaryotic cells
Gametophyte – haploid sexual generation, develops antheridia and archegonia
Sporophyte – diploid asexual generation mostly with true roots, stem and leaves
Thallus – A haploid plant body, without root stems and leaves, in nonvascular plants
Overview: The Greening of Earth
•
For the first 3 billion years of Earth’s history, the land was lifeless.
•
Thin coatings of cyanobacteria existed on land about 1.2 billion years ago.
•
About 500 million years ago, plants, fungi, and animals joined the cyanobacteria.
•
By about 385 million years ago, taller plants appeared, leading to the formation of the first
forests.
More than 290,000 species of plants inhabit Earth today
1. Plants are multicellular, autotrophic, eukaryotes.
2. Plants originated from ancestral green algae and the closest relatives today are stoneworts
(Charophyta) like Chara.
Adaptations for land life:
Mineral absorption helped by association with fungi – mycorrhizae
3.
4. Conserve Moisture: a) All aerial parts are covered by a waxy Cuticle b) Sex organs are covered by a
sterile jacket of cells c) stomata – small pores to regulate water loss from leaves
5. Reproduction on Land: A multi-celled Sporophyte is formed to produce Spores by Meiosis. The
dispersal by spores proved a good adaptation to live on land.
6. Vascular tissues: Xylem – airtight water channels; Phloem – special channels for passing organic
molecules
7. Now main plant groups include Nonvascular plants having liverworts, hornworts and mosses;
Seedless vascular plants include Ferns and fern like plants; Seeded plants include Gymnosperms,
including pines and cycads and Angiosperms, flowering plants.
8. Nonvascular Plants:
I.
This is not a clade and is polyphyletic.
II.
Main plant is gametophyte (n) and develops sex organs with sterile jackets, male sex organs are
antheridia and produce biflagellate sperms. Female sex organs are Archegonia and produce
eggs. Fertilization leads to protected embryo and sporophyte (2n). Sporophyte has foot, seta
and capsule. Foot absorbs food from female gametophyte. Seta projects the capsule. The
capsule produces spores by meiosis. Spores germinate to form gametophyte.
III.
Habitat – Live in moist and shady places. Some can live in dry places and have growth only in
rainy days.
1
IV.
This group has 3 phyla:
9. Liverworts – Hepatophyta (Marchantia polymorpha): Thallus is flat and dichotomously branched.
Upper region has polygonal areas with branched filaments of green cells lying in chambers with air
pores. Lower region stores food and bears unicellular rhizoids for anchoring to substratum.
V.
Upper region has gemma cups with gemma. Each gemma is green, multicellular and has 2
notches with growing points and asexually grows into 2 plants.
VI.
Sporophyte has foot seta and capsule. Capsule has diploid sporocyte cells. Each sporocyte
undergoes meiosis to produce 4 haploid spores. The capsule also has dead long elaters. The
elaters move when conditions are dry and help in release of spores under suitable conditions.
VII.
Hornworts – Anthocerophyta (Anthoceros): Gametophyte is flat and develops long sporophytes
that look like horns.
Liverworts – Hepatophyta Marchantia
Hornworts – Anthocerophyta Anthoceros
Mosses – Bryophyta - Polytrichum
1 Thallus is flat, dichotomously
branched, upper green for
photosynthesis and lower for
storage
Thallus is flat, rosette or ribbon
shaped, many species form
associations with Nostoc
Thallus vertical with stem and leaf like
green parts for photosynthesis
2 Rhizoids unicellular unbranched
Rhizoids unicellular unbranched
Multicellular and branched
3 Asexual reproduction by gemmae
absent
absent
4 Antheridia and archegonia on
separate vertical gametophores;
antheridia in chambers and
archegonia on underside
Archegonia are not distinct and
continuous with surrounding tissue,
distinct antheridia lie in chambers
Antheridia and archegonia develop on
top of stem like branch and leaf like
structures surround them
5 Capsule has elaters but no stomata
or green tissue
Capsule has elaters, stomata and
green tissue
Capsule has peristome, stomata and
green tissue
6 Spores directly form plant
Spores germinate into protonema
Spores germinate into protonema
VIII.
Has horn shaped long sporophytes
Mosses – Bryophyta (Polytrichum and Sphagnum):
IX.
Gametophyte is vertical and has stem like and leaf like parts but are not true due to lack of
vascular tissue. Rhizoids are multicellular branched hair like structures. Antheridia and
archegonia develop on top of stem like branch and leaf like structures surround them.
X.
Bryophyte sporophytes consist of a foot, an elongated stalk (the seta), and a capsule.
XI.
Embedded in the archegonium, the foot absorbs nutrients from the parent gametophyte.
XII.
The seta or stalk conducts these materials to the sporangium or capsule, which uses them to
produce spores by meiosis. One capsule can generate up to 50 million spores.
XIII.
In most mosses, the seta becomes elongated, elevating the capsule to enhance spore dispersal.
2
XIV.
In most moss species, the upper part of the capsule features a ring of interlocking, tooth-like
structures known as the peristome.
XV.
Spores germinate to produce branched filamentous juvenile stage, Protonema. It develops buds
which grow into adult plants, gametophores.
XVI.
Dominant generation is Gametophyte and has root like unicellular or multicellular Rhizoids for
absorption of water and minerals and anchor the gametophyte.
XVII.
Male sex organs called Antheridia – produce sperms and female sex organs called Archegonia –
have eggs inside. Sex organs produce gametes by Mitosis. Fertilization needs external water of
rain or dew for sperms to swim and reach inside ready archegonia. Fertilization leads to
development of embryo and Sporophyte by mitotic divisions.
XVIII.
Sporophyte is dependent on The Gametophyte. The Sporophyte has foot seta and capsule and
lacks vascular tissues xylem and phloem and also roots, stem or leaves. Sporophyte produce
spores by Meiosis. The spores germinate to produce gametophyte.
XIX.
Alternation of generations – Gametophyte  gametes  Sporophyte  spores  again
gametophyte and cycle goes on.
1. In Non-Vascular Plants, liverworts and mosses, main plant is Gametophyte, haploid sexual
generation. Zygote divides with Mitosis to form a multicellular Sporophyte, diploid asexual
generation but the Sporophyte remains attached to gametophyte and is dependent on it.
Sporophyte lacks xylem and phloem, the vascular tissues. Sporophyte produces haploid spores by
meiosis. Spores germinate to directly form gametophyte in liverworts. In hornworts and mosses
spores germinate to produce branched alga like filamentous Protonema. Protonema develops adult
gametophytes by developing buds.
2. In Seedless Vascular plants like ferns the main plant body is a Sporophyte and has xylem and
phloem. It is also differentiated into true roots, stem and leaves. Sporophyte produces spores by
3
Meiosis. Spores germinate to form a heart shaped, flat, green, tiny gametophyte called Prothallus.
Prothallus bears female sex organs Archegonia, just behind apical notch, in maximum thick part.
Prothallus also bears male sex organs Antheridia near posterior end. Therefore ferns exhibit an
alternation of 2 independent generations.
Seedless Vascular Plants have sporophyte dominant generation. It has true roots, stem and leaves due
to development of vascular tissues xylem and phloem. Gametophyte generation is reduced but
independent. Leaves are micorphylls with only one vein. Sporangia are present in axil of modified leaves
sporophylls. The clusters of sporophylls form spikes or strobili. Most plants in this group are
homosporous, produce only one kind of spores. Gametophyte is bisexual and has both archegonia and
antheridia.
Plants in this group have 2 phyla:
4
1. Lycophyta has club mosses (Lycopodium) and spike mosses (Selaginella). Club mosses are
homosporous. Spike mosses, like Selaginella, are heterosporous and has microsporophylls
bearing microsporangium and megasporophylls having megasporangium in axil.
2. Monilophyta or Pterophyta has horse-tails (Equisetum), Ferns (Dryopteris, Adiantum) and
whisk ferns (Psilotum). Refer to table 29.1, images and descriptions in lab manual for
comparison of these groups of plants.
In Gymnosperms like Pines the dominant plant body is Sporophyte and has root, stem and leaves. It has
vascular tissues Xylems and phloem. In addition it developed Pollens and Seeds to become more
successful on land. The plants bear 2 types of cones – male cones and female cones.
Pollen (Male) Cone  microsporophyll microsporangium  microspores (Pollen)  pollination 
sperm
Ovulate (Female cone) megasporophyll megasporangium = ovule female gametophyte  egg
There are no flowers therefore no ovary is present. The seeds remain naked.
Gymnosperms have 4 phyla:
1.
2.
3.
4.
Cycadophyta ( Cycas):
Ginkgophyta (Ginkgo biloba):
Gnetophyta (Gnetum):
Coniferophyta (Pinus):
Refer to table 30.1, images and descriptions in lab manual for characters of these groups of plants.
In Angiosperms just like gymnosperms dominant generation is Sporophyte, root-stem-leaves are
present. Xylem and phloem are present. But seeds develop in fruits. Flowers and fruits are present.
OVULE  SEED;
OVARY  FRUIT
5
Flowers lure insects and other animals to pollinate flowers. Pollination by insects/animals is more targetoriented and more efficient. Fruits invite them to disperse seeds.
Flower has modified leaves. Sepals - The outermost green ones protect the young flower. Petals – inner
to sepals, are colored or white. The petals attract insects/animals and may have nectar. Stamens- male
part– have stalk like part = Filament and upper swollen part = Anther, having pollens. Pistil-female part –
is formed of 3 parts. Ovary is the lowermost swollen part having ovules. Style is the stalk like middle part
and upper Stigma. The stigma is sticky and receives pollen during pollination.
The 2 major groups of flowering plants are monocots and dicots (Eudicots).
Characteristic
Monocots (Corn)
Dicots = Eudicots (Pea)
1.
1
2
2. Venation: arrangement of veins in leaves
parallel
Net like
3.
3 or multiple of 3
4 or 5 or its multiple
scattered
Arranged in a ring
# of cotyledons = embryonic leaves in seed
# of floral parts (petals, stamens etc.)
4. Vascular bundles in stem
6