Plant Kingdom 2 Flashcards
describe basic features of bryophytes
Bryophytes are known as amphibians of the plant kingdom because they need water to
complete their life cycle.
Bryophytes are the first land plant.
iii. Bryophytes are not considered as the successful land plants because vascular tissue is
absent and they need water for fertilization. The process of water transport in bryophytes
takes place with the help of Parenchyma.
iv. Roots are absent in bryophytes.Instead they have root like structure called rhizoids Stem like and leaf like structure of bryophytes are
functionally similar to the stem and leaves of higher plants.
v.
Bryophytes are sciophytes, i.e. bryophytes prefer to grow in moist and shady places.
vi) they are monoecious . has both male/female organs on same plant
explain male sex organ in bryophytes
-> antheridium- multicellular jacketed
- has spore mother cells whcih undergo meiosis to form gametes antherozoids(comma shaped, biflagellate)
explain female sex organ in bryophytes
-> archegonium
-multicellular jacketed
-it is flask-shaped
-the end of the neck of flask has hygroscopic cells whcih absorb water. they absorb water and then burst and cells lining the neck also burst. The antherozoids sense this and move towards the egg. This is chemotactic mvmnt.
explain sexual reproduction in bryophytes
In Bryophyta, fertilization takes place by zoidogamy i.e. male gamete reaches the female
gamete and fertilizes it.
vi. As a result of the fertilization, a diploid zygote is formed. Zygote does not undergo
reduction division (meiosis) immediately. This zygote initiates the sporophytic generation.
Sporophytic generation is a diploid stage.
vii. Zygote further develops by mitosis and forms sporophyte. The sporophyte of bryophyta is
not differentiated into root, stem and leaf but it is made of foot, seta and capsule so it is
known as Sporogonium.
what are the two types of germination of spore cells
The germination of spores is direct or indirect. In Liverworts & Hornworts the
germination of spore is direct i.e. each spore forms a gametophyte after germination i.e.
each spore forms one thallus.
But the germination of spores in Mosses is indirect. In mosses a multicellular filamentous
body is formed after the germination of spore. This filamentous body is known as
protonema. Now buds are formed on protonema. Each bud grows and form a
gametophyte or new plant. Mosses are gregarious in nature because they appear in
group.
what are the two types of protonema
In moss plants secondary protonema is formed by fragmentation of primary protonema or
by erect gametophyte or by the buds of primary protonema and this secondary
protonema again produces buds and form new gametophyte plants (leafy shoots).
Note : (1) Protonema developed from spores is called primary protonema and the
protonema developed from parts other than spores are known as secondary
protonema.
describe liverworts/hepaticopsida
(i)
(ii)
All the bryophytes included in this class are liver like in shape, (eg. Marchantia) or
flat (eg. Riccia) so they are known as liverworts.
Plant body of this group is thallus like and dorsiventral. Rhizoids and scales are
present on thallus.. Rhizoids are unicellular and unbranched. Scales are
multicellular.
(iii) The leafy members (eg. Porella) have tiny leaf like appendages in two rows on the
stem like structures.
(iv) The sporophyte of Liverworts completely depends on gametophyte for food,
water and habitat.
The sporophyte of Liverworts is made up of foot, seta and capsule. (In Riccia the
sporophyte is made up of only capsule).
(vi) True Elaters are present in sporophyte of some members of liverworts.
(eg. Marchantia). Elaters are hygroscopic and they help in dispersal of spores.
Examples of Liverworts –
Riccia
Marchantia
Porella
describe anthocerotopsida
The plant body of this group is thallus like. Rhizoids are present on thallus but
scales are absent. Rhizoids are unicellular and unbranched.
(ii) The sporophyte of Hornworts is divided into foot and capsule.
(iii) The sporophyte of Hornworts is not completely dependent on its gametophyte i.e.
it is semiparasite
(iv) sporophytr has pseudoelaters for spore dispersal.
example:
-anthoceros
describe mosses/bryopsida
The plant body of mosses is made up of
stem like, leaf like and rhizoids (roots like). The Rhizoids present in the plants of this
class are multicellular, branched and obliquely septate.
The presence of leaf like structure in gametophyte is the unique character of Moss
because in plant kingdom any gametophyte do not have leaf like structure. They
consist of upright slender axis bearing spirally arranged leaves.
The sporophyte in mosses is more elaborated (developed) than that in liverworts.The sporophyte of mosses is also partially dependent like that of hornworts. i.e. it is
photosynthetic. The moses have an elaborate mechanism of spore disperal.
Note : Peristomial teeth are present in moss sporophyte which help in spores dispersal.
peristome teeth are teeth like strructures. They are closed when spore are being formed. They are covered by an outer covering called operuclum (which is 2n). Once spores are developed, the operculum falls and the peristome teeth open and disperse the spores.
describe pteridophytes
first successful terrestrial plant
but not complete;y successfull as water is still needed for fertilisation
Pteridophytes are also called as vascular cryptogames. Pteridophytes are vascular plants
i.e. xylem and phloem are present in it.
they also have true roots.
explain the roots and stem of pteridophytes
The primary root remains alive for short period. After some time it is replaced by
adventitious roots.
Stem is erect or prostrate. When the stem is underground, it is known as rhizome.
what are two types of pteridophytes based on leaf size
- First in which stem is smaller while leaves are larger. They are known as megaphyllous Pteridophytes. Eg: FERNS
- Second, in which stem is larger and leaves are smaller. They are called as
microphyllous Pteridophytes.
e.g. Selaginella
what are the two types of leaves on sporophyte
The leaves on which sporangia are formed are called sporophylls (reproductive leaves)
and normal photosynthetic leaves are called trophophylls (vegetative leaves).In pteridophyta, sporophylls are also photosynthetic. This is a unique character of
pteridophyta.
what are sporangia? where they are found?
Formation of spores takes place in sporangia. Sporangia are formed at the abaxial surface
of leaves.
Sporangia
are present in groups, these groups are called sorus (Plural-sori). Sori are found on
sporophylls.
Spore mother cells are present in sporangia. Spores are formed with in sporangium by
meiosis in spore mother cells and these spores start the gametophytic generation. Germinatoion of spores is exosporic ( outisde plant body)
explain the gametophyte of pteridophyte
In soil, an inconspicuous, small and multicellular gametophyte is formed by the
germination of each spore, which is known as prothallus. The formation of gametophyte
takes place in the soil therefore it is free (independent) and mostly photosynthetic. It contains rhizoids for absorption of water. It is non vascular. In homosporus pteridophytes, gametophyte is monoecious. It is usually heart shaped. It bears archegonia and antheridium.
In some pteriophytes prothallus is saprophytic.
