Kingdom Planate
INTRODUCTION
§ Includes all eukaryotic multicellular and chlorophyllous living
organisms, which have cell wall made up of true cellulose.
§ Majority of members are autotrophic but few are parasite e.g.:
“Cuscuta”
§ They have localized growth, regions of growth lying primarily at
the extremities that is root and stem apices.
CLASSIFICATION OF KINGDOM PLANTAE
Kingdom planatae is
divided into tow sub-kingdom on the basis of presence or absence of vascular
tissue (xylem and phloem).
A – SUB-DIVISION – BRYOPHYTES
(NON-VASCULAR)
§ Class Hepatica (Liverworts)
§ Class Musci (Mosses)
§ Class Anthroccrota (Hornworts)
B- SUB-DIVISION – TRACHEOPHYTES
§ Class Psilopsida (Psilopsids)
§ Class Lycopsida (Club Mosses)
§ Class Sphenopsida (Horse Tails)
§ Class Pteropsida (Ferns)
§ ClassSpermopsida (Seed Plants)
SUB –DIVISION BRYOPHYTA (AMPHIBIAN PLANTS) OR (NON-VASCULAR
PLANTS)
§ Absence of lignin-fortified tissue to support tall plants on
land.
§ Members of this sub-division usually sprawl horizontally as mats
over a large surface.
§ Always have a low profile (1-2cm-20cm tall).
Regular
heteromorphic alternation of generation is present w/t gametophytes dominancy
(Gametophytes large and long lived).
§ Sporophyte stage of bryophytes is generally smaller and shorter
lived, and it depends on gametophyte for water and nutrients.
§ The diploid sporophyte produces haploid spores via meiosis in a
structure called “sporangium”
§ The tiny, spores, protected by sporopollenim, disperse and give
rise to new gametophytes.
§ All members of bryophytes need water to reproduce.
§ Gametes produce within reproductive structures “Gametangia”
(Male-Antheridia and Female-Archer-gonium)
§ Antheridium produces flagellated sperm while female archegonium
contains one egg (ovum).
§ Fertilization occurs w/t in the archegonium
§ Zygote develops into an embryo within the protective jacket of
Archegonium.
§ Windblown spores disperse the speies.
§ All bryophytes belong to Silurian/Devonian period
(345-395Million yrs. Ago.)
ADAPTATION OF BRYOPHYTES TO LAND HABITAT
All Bryophytes show
amphibious form of land plants. Following are main adaptations exhibited by
them.
a. Rhizoid for water absorption
b. Conservation of water
c. Absorption of CO 2
d. Heterogamy
e. Protection of reproductive cells
f. Formation of embryos
a. Rhizoid for water absorption
b. Conservation of water
c. Absorption of CO 2
d. Heterogamy
e. Protection of reproductive cells
f. Formation of embryos
CLASSES OF BRYOPHYTES
1-MUSCI (MOSSES)
§ Plants grow in a tight pack, in the form of mat, in order to
hold one another up.
§ Mat of moss possess spongy quality and enables it to absorb and
retain water.
§ Rhizoids are elongated cells or cellular filaments of mats which
grip the substratum.
§ Photosynthesis occurs in upper part of the plant w/c has many
small stem like and leaf like appendages. E.g Funaria.
2-HEPATICAE (LIVERWORTS)
§ Usually present in tropical areas
§ Plant body is divided into lobes somewhat of the lobed liver, of
an animal.
§ These plants are less fimiliar than Mosses.
E.g Marchantia
3- ANTHROCERATAE:- (HORNWORTS)
§ These plants resemble w/t liverworts, but are differentiated by
their sporophytes plants.
§ Sporophyte are elongated capsules that grow like horn from mat
like gametophyte.
§ Sporophyte has stomata and chloroplast, performs photosynthesis
§ Sporophyte plant can survive even often the death of gametophyte
due to presence of Meristem.
§ Meristem is a specialized tissue, which keeps on adding new
cells in sporophyte plant.
§ Hornworts are the most advanced members of bryophytes.
E.g Arthroceros
SUB-DIVISION TRACHEOPHYTA (VASCULAR PLANTS)
Main characters are
as follow,
§ Conducting vessels Xylem and Phloem are present in plant body.
§ A protective layer of sterile “Jacket” cells around reproductive
organs are present.
§ Multicellular embryos retained within the archegonia.
§ On aerial parts protective covering “Cuticles” is present w/c
prevents excessive loss of water during hot climate.
§ In life cycle Sporophyte stage is dominant.
CLASSES OF TRACHEOPHYTES
1-PSILOPSIDA
§ These are the fossil representatives of the vascular plants,
belonging to “Silurain period” and “Devonian Period”
§ Sporophytes are simple dichotomously branching plants.
§ True leaves and true roots absent.
§ Underground stems that contain unicellular rhizoid similar to
root hairs.
§ The aerial stems are green and carry out photosynthesis.
§ Lacking secondary growth due to absence of “Cambium”
§ Reproductive structure “Sporangia” develop at the tips of some
of the aerial branches.
§ Meiosis produces haploid spores, within the sporangia.
E.g. Rhynia,
Psilotum Temesipteris
A) RHYNIA (FIRST VASCULAR
PLANT)
§ One of the most primitive vascular plant
§ It is an extinct genus, was named often the village “Rhynia of
Scotland where the first fossils of Rhynia were discovered.
§ It belongs to Devonian period, which started about 400 million
years ago.
§ The fossils of this plant are so well preserved that the stomata
are still intact.
STRUCTURE
§ The plant body (Sporophyte) was simple.
§ It consisted of slender, dichotomously branched creeping
rhizome, bearing erect, dichotomously branched aerial stem.
§ Instead of roots, rhizoids were given out from rhizome.
§ The aerial branches were leaf-less having terminal fusiform
naked sporangia.
MICROSCOPIC STRUCTURE
§ The internal structure of branches show a solid central core of
vascular tissues surrounded by Cortex.
§ The outer most layer is Epidermis having stomata.
§ The vascular tissue is differentiated into centrally placed
xylem and surrounded phloem
(FIGURE 9.06(a)
Reconstruction of Rhunia) TEXT BOOK BIO-XI Pg# 170
B) PSILOTUM AND TEMESIPTERIS
(LIVING SPECIES OF PSILOPSIDA)
§ Sporophyte plant produce spores, which give rise to minute
subterranean gametophytes.
§ Each gametophyte bears both female reproductive organ Archegonia
and male reproductive organ Antheridia w/c produce both egg and sperm
respectively.
§ As a result of fertilization a diploid zygote is formed which
develops into sporophyte plant.
§ Sporophyte stage of life cycle is dominant, but haploid
gametoplyte stage is still relatively large.
EVOLUTION OF LEAF
The leaf is the most important organ of a green plant because of its photosynthetic activity. Leaves are of tow types
1. Single veined leaves- Contain only one vein
2. Poly veined leaves- Contain two or more veins
The leaf is the most important organ of a green plant because of its photosynthetic activity. Leaves are of tow types
1. Single veined leaves- Contain only one vein
2. Poly veined leaves- Contain two or more veins
1- EVOLUTION OF SINGLE-VEINED
LEAF
§ It is assuming that a thorn like out growth emerged on the
surface of the naked stem.
§ With an increase in size of the leaf, the vascular tissues were
also formed for the supply of water and support to the leaf.
§ Another possibility is that a single veined leaf originated by a
reduction in size of a part of the leafless branching system of the primitive
vascular plants.
2-EVOLUTION OF POLY-VEINED LEAF
§ These are the evolutionary modifications of the forked branching
in the primitive plants.
§ The first step in the evolution of this leaf was the restriction
of forked branches to a single plane.
§ The branching system become flat.
§ The next step in the evolution was filling the space b/w the
branching and the vascular tissues.
§ The leaf so formed looked like the webfoot of a duck.
(Fig#9.7-9.8From
Text. Book)
2-LYCOPSIDA(THE CLUB MOSSES)
§ These plants belong to middle Devonian and carboniferous
periods.
§ They were very large trees that formed the earth’s first
forests.
§ Only five living genera of this group are present.
§ Two members, selaginella and lycopodium are common in many areas
of Pakistan
§ These plants have true branched underground roots.
§ True leaves also present w/c have arisen as simple scale like
outgrowth (emergence) from the outer tissues of the stem.
§ Specialized reproductive leaves bearing sporangia on their
surfaces, are present, such type of leaves are known as “Sporophylls”.
§ In some members, the sporophylls are collected on a short length
of stem and form cone like structure “Strobilus”.
§ The cone is rather club-shaped; hence name “Club-Mosses” for the
lycopsids.
§ Gametophytes plant may be homosporous or heterosporous .
A) HOMOSPOROUS GAMETOPHYTES
§ Spores produced by sporophyte plant are all alike, and each give
rise to a gametophytes that bear both archegonia (female reproductive
structure) and antheridia (male reproductive structure)
Example Lycopodium
(Running pine or ground pine)
B) HETEROSPOROUS GAMETOPHYTES
§ Sporophyte (2n) plant produces two types of sporangia, which
produced different kinds of spores.
§ One type of sporangium produces very large spores called
“Megaspores,” which develop in female gametophytes bearing archegonia.
§ Other type of sporangium produces small spores called
“Microspores, which develop into male gametophytes bearing antheridia.
§ That’s mean sexes are separate in the gametophytes generation
(Heterosporous).
Example:
Selaginella.
EVOLUTION OF SEED
Seeds are evolved from primitive spores.
Seeds are evolved from primitive spores.
STEPS OF EVOLUTION
1. PRIMITIVE SPORES
All spores of specie are nearly identical in size, structure and function.
All spores of specie are nearly identical in size, structure and function.
2. HETEROSPORES
§ There are many vascular plants that form two kinds of spores,
these plants are said to be “Heterosporous” and spores are called “Heterospores.”
§ These spores on germination give rise to two different types of
plants.
A) MALE SPORE: It
produces sperm forming gametophyte plant.
B) FEMALE SPORE: It grows into egg forming gametophyte.
B) FEMALE SPORE: It grows into egg forming gametophyte.
3. PROTECTION OF HETEROSPORES
§ The two different kinds of spores are formed in two different
kinds of sporangia.
§ Various enveloping structures develop in order to protect these
spores.
§ Certain fern like plants first developed seed like structures,
each of their sporangia, containing one or more female spores, was surrounded
by little branch like out growth structure forming “Integument.”
4. PERSISTANCE OF FEMALE SPORES
§ Instead of being shed from the sporangium, the female spores are
retained and protected inside the integument.
§ The female spore develops into a tiny female gametophyte
protected by the integuments.
5. FORMATION AND STRUCTURE OF
SEED
§ Seed is formed as the result of fertilization of male spore with
this protected female spore.
§ Immature seed is called “Ovule.”
§ Ovule is protected by integuments and it contains great
quantities of food.
§ Ovule not only protects the female gametophyte from the
environment but also provides food for the new off springs that is produced
when the seed matures and germinate. The development of seed has given the
vascular plants better adaptations to their environment.
3. SPHENOPSIDA (THE HORSE
TAILS)
§ These plants belong to late Devonian and Carboniferous period.
§ Only one living member “Equisetum” commonly called “Horse-tail”
exists today.
§ Ancient sphenopsids were large trees but now most of these are
small (Less than one meter).
§ Coal deposits of today was formed from the dead bodies of those
plants.
§ These plants possess true roots, stems and leaves.
§ Stems are hollow and are jointed, whorls of leaves occur at each
joint.
§ Secondary growth absent, because modern species do not possess
cambium.
§ Spore are born in terminal cones (Strobili) and all are alike
(i.e. plants are homosporous) and give rise to small gametophytes that bear
both archegonia and antheridia (i.e. the sexes are not separate).
4. PTEROPSIDA (THE FERNS)
§ These plants belong to Devonian and Carboneferous Period and
then decline in Paleozoid Period.
§ They are very well developed plants having vascular system with
true roots, stem and leaves.
§ Leaves are probably arisen from flattened web branched stems.
They are large and provide much greater surface area for photosynthesis.
§ Leaves of Ferns are sometimes simple, but more often they are
compound, being divided into numerous leaflets.
§ In most modern ferns of temperate regions, the stems are
prostrate on or in the soil, and the large leaves are only part normally seen.
SPOROPHYTIC STAGE
§ The large leafy plant (fern) is diploid sporophytic phase.
§ Spores are produced in sporangia (Reproductive structure) located
in clusters on the underside of some modified leaves “Sporophyll.”
§ Most modern ferns are homosporous i.e. all these spores are
alike.
§ Vascular sporophytes can live in drier places and grow bigger.
GAMETOPHYTE STAGE
§ After germination, the spores develop into gametophytes that
bear both archegonia and antheridia.
§ These gametophytes are tiny (less than one centimeter wide),
thin and often more or less heart-shaped.
§ Free-living, non-vascularized gametophytes can survive only in
moist places, their sperms are flagellated and water is required for
fertilization.Young sporophyte develops directly from the zygote without
passing through any protected seed like stage.
(LIFE CYCLE OF FERN-TEXT BOOK PAGE # 166 NEW ADDITION)
ALTERNATION OF GENERATION
§ In Kingdom Plantae, life cycle of many plants is completed in
two stages or generations known as Gametophyte and Sporophyte.
§ The two generations normally differ from each other in
morphology, reproduction and number of chromosomes.
§ The gametophyte is haploid and reproduces sexually by forming
the gametes, while the sporophyte is diploid and reproduces a-sexually by
forming the spores.
§ The two generations regularly alternate with each other and
therefore, the phenomenon is called “Alternation of generation” (Heteromorphic).
§ In Bryophytes, the main plant itself is the Gametophyte while
the sporophyte is reduced.
§ In Tracheophytes, the main plant is “Sporophyte” and the
“Gametophyte” is reduced.
5. SPERMOSIDA (THE SEED PLANTS)
§ First appeared in late Devonian and became dominant in
Carboniferous Period.
§ Gametophyte stage is even more reduced than in the ferns, and
non-photosynthetic or free-living.
§ The sperms of most modern species are not independent
free-swimming flagellated cells.
§ Young embryo, is enclosed within a seed coat and can remain
dormant for long periods.
§ Spermosida can be divided into two main sub-groups, which are as
follows:
i) Gymnosperms
ii) Angiosperms
ii) Angiosperms
I) GYMNOSPERM
These plants have naked seed because ovules are not covered by ovary i.e. fruit is absent.
Sub-divisions of Gymnosperms are
a) Cycads
b) Gnetae
c) Ginkgo
d) Conifers
These plants have naked seed because ovules are not covered by ovary i.e. fruit is absent.
Sub-divisions of Gymnosperms are
a) Cycads
b) Gnetae
c) Ginkgo
d) Conifers
A) CYCADS’
§ They have arisen from the seed ferns.
§ These plants appeared in “Permian Period” and Mesozoic Period
and declined in Cretaceous Period.
§ They possessed large palm like leaves with short height stems.
§ Living species commonly found in tropical regions and also known
as “Sago Palms.”
§ Nine living genera with over a hundred species exist today.
§ Cycads and its relatives.
B) GINKGOAE
§ Mostly contains extinct species, only one living specie, “the
Ginkgo” which is also known as “Maiden Hair Tree.”
§ Ginkgo often planted as lawn tree.
E.g: Ginkgo Biloba.
C) CONIFERS
§ Most familiar and best-known group of gymnosperms.
§ Leaves are small evergreen needles or scales with an internal
arrangement of tissues.
§ Reproductive organs are cone like modified leaves.
E.g: Pinus.
PINUS
This plant belongs
to Gymnosperms. It includes about 90 species.
HABIT AND HABITAT
§ It is distributed world-wide mostly in northern hemisphere. 30
species are found in the Himalayas. Some are reported in the planes of Punjab.
MORPHOLOGY
§ The pinus plant belongs to the “Sporophytic Phase.”
§ It is a tall tree, pyramidal in form and gives a conical
appearance and therefore commonly grouped under “Conifers.”
§ It is well differentiated into stem, root and leaves.
STEM
It is erect, cylindrical, solid and covered with thick, rough and brownish bark. The branches are dimorphic,
It is erect, cylindrical, solid and covered with thick, rough and brownish bark. The branches are dimorphic,
§ Branches of unlimited growth or long shoot.
§ Branches of limited growth or dwarf shoot.
ROOTS
Underground root system is formed by “Tap Roots” which disappear early and only lateral roots persist later on.
Underground root system is formed by “Tap Roots” which disappear early and only lateral roots persist later on.
LEAVES
It bears two types of leaves (dimorphic condition)
a) Scale leaves
b) Foliage leaves
It bears two types of leaves (dimorphic condition)
a) Scale leaves
b) Foliage leaves
A) SCALE LEAVES
§ Thin, membranous small scale like structures.
§ Provide protection and do not help in photosynthesis.
B) FOLIAGE LEAVES
§ Only develop on dwarf shoots.
§ Number of foliage leaves is fixed for particular specie.
§ Each leave is needle shaped, simple green therefore also known
as “Needles.”
§ They have smooth surface and are evergreen and persistent.
LIFE CYCLE OF PINUS
The adult plant of
Pinus represents the “Sporophytic Phase” of life cycle.
The sporophytic plant body of pinus reproduces asexually by means of spores and after passing through “Gametophytic Phase” of the life cycle again produce Sporophytic plant, showing distinct Alternation of Generation.
The sporophytic plant body of pinus reproduces asexually by means of spores and after passing through “Gametophytic Phase” of the life cycle again produce Sporophytic plant, showing distinct Alternation of Generation.
1. SPOROPHYTIC PHASE
§ The sporophytic plants of Pinus are mostly monoecious i.e. male
and female cones are found on same plant.
§ Special reproductive organs called “Cones,” developed on it.
A) MALE CONE OR O-STROBILUS
§ The male cones occur in clusters near the end of long branches
at the place of dwarf shoot. (Dwarf shoots are replaced by male cone).
§ Each male cone is simple ovoid structure 3-4 cm in length.
§ It has got single centrally located cone axis around which are
arranged spirally, many scaly microsporophylls (60-135).
§ Each microsporophyll has an expanded triangular central part and
a stalk like base.
§ Each microsporangium, which is born on the lower side bears
numerous “Pollen grain mother cells.”
§ When the microsporangium matures, on its lower side a horizontal
slit is formed through which numerous Pollen grains are liberated and dispersed
by wind.
§ Each pollen grain is winged structure and yellow in colour.
B) FEMALE CONE OR O-STROBILUS
§ The female cones are developed laterally in the axis of scale
leaves.
§ The female cones are much bigger, woody, dry and hard structure.
§ The young female cone is reddish green structure. Each female
cone consists of a central axis to which are attached the “Megasporophyll.”
§ Each megasporophyll on its surface has two ovules.
§ Each ovule is orthosporous and consists of a central mass of
tissue, surrounded by a single integument, made up of 3 layers.
§ The integument bears a wide gap, the microphyle.
§ Within the megasporangium, megaspore mother cells are present,
which undergoes reduction division to produce a “Megaspore.”
§ Only one megaspore is functional, however the other three
degenerate.
2. GAMETOPHYTE PHASE
§ The spores are the units of gametophytic phase of life cycle.
§ In case of Pinus the spores are of two types, microspores and
megaspores.
A) MALE GAMETOPHYTES
§ Microspore is a unit of male gametophyte.
§ Each microspore or pollen grain is a unicellular body, covered
with an outer layer, “Exine,” thick and heavily culticularized, while the inner
layer, the “Intine” is very thin.
§ The Exine forms the balloon shaped wings on either side, which
help in pollination.
§ The microspore is at this, four celled stage (consisting of one
generative cell and two prothalial cells and a tube cell).
B) FEMALE GAMETOPHYTE
§ The Megaspore is the first cell of female gametophyte.
§ The functional megaspore increases in size and forms a complete
cellular female gametophyte, also known as “Endosperm.”
§ The “Archegonia” are formed towards micropylar side.
§ The cells of the endosperm or Archegonia initial cell divides
and forms the central cell.
§ The central cell forms the venter canal cell and a large egg
cell.
POLLINATION
In case of Pinus, Pollination
is effected by wind (Anemophyllous).
FERTILIZATION
1. The pollen
grains reach the apex of the Archegonium.
2. The pollen tube carrying the two male gametes and the tube nuclei comes in contact with the archegonium.
3. The tip ruptures, discharging its contents into the egg.
4. One of the male gamete fuses with the egg nucleus and unites forming the oospore or zygote.
5. The second male gamete along with the tube and tube nuclei disintegrate.
2. The pollen tube carrying the two male gametes and the tube nuclei comes in contact with the archegonium.
3. The tip ruptures, discharging its contents into the egg.
4. One of the male gamete fuses with the egg nucleus and unites forming the oospore or zygote.
5. The second male gamete along with the tube and tube nuclei disintegrate.
PINUS SEED
§ Fertilized ovules get transformed into seeds.
§ Seeds are small elongated and winged.
GERMINATION OF SEED
The seed undergoes into a condition of dormancy when the conditions are favourable, the seed absorbs moisture and the embryo resume growth.
The seed undergoes into a condition of dormancy when the conditions are favourable, the seed absorbs moisture and the embryo resume growth.
STRUCTURE OF OVULE
§ Ovules are female part of flower, form seed after fertilization.
§ Microscopic study of an ovule reveals following structural
features of an ovule.
1. FUNICLE
It is slender stalk
of ovule through which it attaches to the placenta.
2. HILUM
It is the point of
attachment of the body of the ovule to its funicle.
3. RAPHE
In the inverted
ovule, the funicle continues beyond the hilum along side of the body of the
ovule forming a sort of ridge, which is called the “Raphe.”
4. CHALAZA
The distal end of
the raphe, which is the junction of integuments and the nucellus is called the
“Chalaza.”
5. NUCELLUS
It is the main body
of ovule.
6. INTEGUMENTS
Nucellus is
surrounded by two coats called the “Integuments.”
7. MICROPYLE
It is the small
opening at the apex of integuments.
8. EMBRYO-SAC
It is a large, oval
cell lying embedded in the nucellus towards the micropyle end. It is the most
important part of the ovule as it bears the embryo. It is further developed,
and in the mature embryo sac following cells can be seen:
A) EGG APPARATUS
§ It is the group of three cells lying towads the micropyle.
§ One cell of the group is the female gamete, the ovum/egg, and
the other two are called “Synergids.”
§ The ovum or egg-cell on fertilization gives the embryo,
synergids get disorganized soon after fertilization.
B) ANTIPODAL CELLS
This is the group of three cells lying at the opposite end of egg apparatus. These have no definite function.
This is the group of three cells lying at the opposite end of egg apparatus. These have no definite function.
C) DEFINITIVE NUCLEUS
In the middle of the embryo-sac there is a distinct nucleus known as a definitive nucleus, which is the fused product of the two polar nuclei.
In the middle of the embryo-sac there is a distinct nucleus known as a definitive nucleus, which is the fused product of the two polar nuclei.
STRUCTURE OF POLLEN GRAIN
§ Pollen grains are male part of flowers, and are contained in the
“Pollen-Sac.”
§ They are very small in size, usually varying from 10 to 200 μm.
§ Microscopic study of a pollen grain shows following features:
1. EXINE
§ It is the outer coat of the pollen grain.
§ It is tough, cutinized layer, which is often provided with
spinous out growths or markings of different patterns, sometimes smooth.
§ It has one or more weak slits or pores called “Germopores.”
2. INTINE
§ It is the inner coat of the pollen grain.
§ It is thin, delicate, cellulose layer lying internal to the
exine.
§ During fertilization in time grows to form pollen-tube.
3. INTERNAL STRUCTURE
§ Each pollen grain contains a bit of cytoplasm on a nucleus.
§ During germination of pollen grain nucleus further divides to
form a “Tube Nucleus,” and a smaller one the “Generative Nucleus.”
§ The generative nucleus soon divides into two male gametes.
0 comments :
Post a Comment