Explain
briefly the following terms with suitable examples:-
(i) protonema
(ii) antheridium
(iii) archegonium
(iv)
diplontic
(v)
sporophyll
(vi) isogamy
Explain briefly the following terms with suitable examples:-
(i) protonema
(ii) antheridium
(iii) archegonium
(iv) diplontic
(v) sporophyll
(vi) isogamy
(i) Protonema –
It is the first stage in the life cycle of a moss, developing
directly from the spore. It consists of creeping, green, branched,
and often filamentous structures.
(ii) Antheridium
– It is the male sex organ
present in bryophytes and pteridophytes and is surrounded by a jacket
of sterile cells. It encloses the sperm mother cells, which give rise
to the male gametes.
(iii) Archegonium
– It is the female sex organ
present in bryophytes, pteridophytes, and gymnosperms. In bryophytes
and pteridophytes, it generally has a swollen venter and a tubular
neck, and contains the female gamete called the egg.
(iv) Diplontic
– It is the term used for the
life cycles of seed-bearing plants (gymnosperms and angiosperms). In
these plants, the diploid sporophyte is dominant, photosynthetic, and
independent. The gametophyte is represented by a single-celled (or a
few-celled) structure.
(v) Sporophyll
– In pteridophytes, the
sporophytic plant body bears sporangia. These sporangia are subtended
by leaf-like appendages known as sporophylls. In gymnosperms,
microsporophylls and megasporophylls are found. These bear
microspores and megaspores respectively.
(vi) Isogamy –
It is a type of sexual reproduction involving the fusion of
morphologically-similar gametes. This means that the gametes are of
the same size, but perform different functions. This type of
reproduction is commonly observed in Spirogyra.
(i) Protonema – It is the first stage in the life cycle of a moss, developing directly from the spore. It consists of creeping, green, branched, and often filamentous structures.
(ii) Antheridium – It is the male sex organ present in bryophytes and pteridophytes and is surrounded by a jacket of sterile cells. It encloses the sperm mother cells, which give rise to the male gametes.
(iii) Archegonium – It is the female sex organ present in bryophytes, pteridophytes, and gymnosperms. In bryophytes and pteridophytes, it generally has a swollen venter and a tubular neck, and contains the female gamete called the egg.
(iv) Diplontic – It is the term used for the life cycles of seed-bearing plants (gymnosperms and angiosperms). In these plants, the diploid sporophyte is dominant, photosynthetic, and independent. The gametophyte is represented by a single-celled (or a few-celled) structure.
(v) Sporophyll – In pteridophytes, the sporophytic plant body bears sporangia. These sporangia are subtended by leaf-like appendages known as sporophylls. In gymnosperms, microsporophylls and megasporophylls are found. These bear microspores and megaspores respectively.
(vi) Isogamy – It is a type of sexual reproduction involving the fusion of morphologically-similar gametes. This means that the gametes are of the same size, but perform different functions. This type of reproduction is commonly observed in Spirogyra.
