MORE ABOUT GYMNOSPERM

MORE ABOUT GYMNOSPERM

SEED FORMATION:-

Seed = (Embryo+ Seed coating)

Fertilisation (In case of gymnosperm)

1. Joibosphinogamy

2. Sphinogamy

• These type of fertilisation occurs in lower Gymnosperm in which male gamete is non-motile. I.e. in Zoidsphinogamy

Sphinogamy:- in higher Gymnosperm male gamete is non-motile and reaches the egg with the help of pollen tube. After pollination make gamete fuses with the egg as the result of which a diploid zygote is formed
        DEVELOPMENT OF ZYGOTE

• Embryo is formed by the development of zygote.After the formation of Embryo ovules is called seed.
• Embryo is enclosed inside the seed.
• Now,this seed rupurted by absorbing water and the embryo germinate to form a disposal plant  (sporophyte)

Life cycle of Gymnosperm is dislomtic.

Gymnosperm(types)

1. Cycadophyte:-Characters are similar to fern

• Plants are megaphyllous or macrophyllous
• Ramenta are present.
• Male gamete are motile.Ex-cycus(A living fossil) are included in this group.

      2. Coniferophyta ;- Maximum plants of this group are extinct.Ex:-Ginkgo- Living fossil.

• Pinus:- it gives us chilgoza and turtenpine oil.
• Cedrus (deodara) :- Known as devdar
• Sequaira:- Red tree.

 

ANGIOSPERM

• The angiosperm are large group of plant which occur in wide range of habitat.
• Smallest angiosperm plant:- Wolfia.
• Largest angiosperm plant- Eucalyptus. 
• They produce flower for sexual reproduction in which male sex organ (stamen), female sex organ (carpel)
• In another of stamen pollen grain are formed after meiosis which are carried by wind or any other agencies to the stigma of the female sex organ.
• Female sex organ consist of ovart in which one or many more ovule are produced.
• Body of the ovulezs is made up of diploid tissues called as Nucleus. One cell of nuclear acts as megaspore mother cell which forms megaspore after meiosis.
• With in ovules megaspore further produce 7 cell with 8 mucleated female gametophyte (embryo sac)
• Each cell of embryo sac is haploid.
• Embryo sac formation is decided by meiosis, so it is haploid (2n)
• Every Embryo sac has a three celled egg-apparatus one egg cell and two synergies at microphyl), 3 antipodes cell at chala and 2 polar nucleus.
• Embryo sac formation is decided by meiosis, so) it is haploid.
• Polar nuclei fused to form diploid secondary nucleus.
• The pollen grain germinate on stigma and produce pollen tube and reach the ovule.
• Pollen tube enters into embryo sac through the gap of release two male gamete.
• One Male gamete fused with the egg cell to form zygote (2n). The other male gamete fuses with diploid secondary nucleus to form (3n), primary endosperm nucleus (PEN).
• PEN forms nutritive tissues known as Endosperm (3n).
• Because of involvement of two fusion this is called double fertilisation. Which is a unique feature of angiosperm.
• Zygote develop ls 8nto embryo and formed new diploid plant on germination.
• After fertilisation ovule convert into seed and not maked but enclosed by fruits.

Nature of the following 

1. Antipodal cell (n) 
2. Synergids (n)

because it6outer layer is mbryo sac (female gametophyte nature is n so all the 7 cell nature is n.)

3. Megasporangium(2 n)- contain mega SMC (2n) so it's nature is 2n.

4.Embryo sac (n)- because it is a female gametophyte so, nature of gametophyte is (n).

5. Pollen grain (n)- (Male gametophyte)

6. Nucleus (2n)- ovule made up of diploid tissues, nature (2n).

7. Megasporophyll (2n)- contain megasporigum nature (2n). So, it's nature is (2n).

8. Anther(2n)- Male reproductive system. Nature of flower is (2n) so, Anther is (2n).
9. Ovule (2n)- later develop into fruit and part of female reproductive part, so its nature (2n)