Amphibian of land plants, Bryophytes, Multiple Choice questions: NEET
🌑General features of Bryophytes:
🔴Occurence - Bryophytes grow in humid ,damp and shady places and hilly areas.
🔴Gametophyte stage -
👉The dominant and main plant body is gametophyte which is haploid .
👉The gametophyte bears unicellular or multicellular rhizoids for attachment with the substrate.
🔴Sex organs -
👉Gametophyte is well developed and bear sex organs. These sex organs are multi-cellular and jacketed.
👉The male sex organ is anthredia and female sex organ is archegonia.
👉Anthredia produces antherozoids or male gamete whereas archegonia produces eggs enclosed in its ventral canal cells.
👉Antherozoid use water as medium and reach to the egg for fertilization.
👉After the fusion, zygote is formed. This zygote does not undergo reduction division and develops into multicellular sporophyte.
🔴Sporophyte-
👉Sporophyte is not free living and depends on gametophyte for nutrition so it is attached with the gametophyte.
👉Sporophyte is differentiated into foot, seta and capsule.
👉Capsule produces haploid spores by the reduction division. These spores germinate and form gametophyte.
👌👌Remember - Bryophytes have alternation of generation with the gametophyte and sporophyte.
🌑Importance of Bryophytes:
🔴Bryophytes, especially mosses, prevent soil erosion caused by running water. They are also involved in the process of succession.
🔴Mosses are an important link in plant succession on rocky areas. They take part in binding soil in rock crevices formed by lichens. Growth of Sphagnum ultimately fills ponds and lakes with soil.
🔴Peat is a dark spongy fossilized matter of Sphagnum. Peat is dried and cut as cakes for use as fuel. Peat used as good manure.
🔵Extra shot of Importance of Bryophytes
Mosses are a good source of animal food in rocky and snow covered areas.Polytrichum is used to remove kidney and gall bladder stones. Sphagnum is used for treatment of eye diseases
🌑Classification of Bryophytes-
Bryophytes are classified into three classes:🌑General features of Liverworts.
🔴Liverworts are present in moist areas , at banks of rivers, damp, soil, bark of trees etc.
🔴Generally the gametophytic plant body is thalloid. Thallus is dorsiventral Sometimes it is foliose or having tiny leaves without midrib.
🔴The leafy members have tiny leaf like appendages in two row on stem like structure.
🔴Asexual reproduction takes place by the fragmentation of thallus.
🔴They also reproduce asexually by the special structure called gemmae or Gemma cup. These are asexual buds that are green and multicellular. Gemmae originated on the thallus of liverworts.
🔴Sexual reproduction takes place in antheridia and archegonia. Both are located on different thallus or same thallus at the dorsal surface.
🔵Extra shot of Importance of Liverworts
Each cell in the thallus contains many chloroplasts; the chloroplasts are without pyrenoid. Sporophyte may be simple in Riccia having only a single capsule or differentiated into foot, seta and capsule in Marchantia. Spores are formed in capsule by meiosis. For Example - Riccia, Marchantia, Pallia and Porella.
🌑General features of Musci or moss
🔴The dominant stage of moss is gametophyte that is differentiated into two stages - Protonema and leafy stage.
🔴Protonema is creeping, green stage and developed directly from the spores. 🔴Leafy stages are developed from the protonema. Leafy stages bear leaves like appendages and are attached with the soil by multicellular rhizoids.
🔴They reproduce vegetatively by fragmentation and budding of protonema. 🔴They do sexual reproduction by producing antheridia and archegonia as a result zygote is formed. The zygote divides by meiosis and produces spores that develop into sporophytes.
🔴In mosses, sporophytes are divided into foot seta capsules and more developed than other groups.
🔴It's capsule has a more advanced mechanism of spore dispersal. For Ex- Funeria, Polytrichum Sphagnum,
🔵Extra shot of Importance of Moss
Marchantia polymorpha has been used to cure pulmonary tuberculosis. Bryophytes are used as packing material for fragile goods, glass wares etc. Some bryophytes act as indicator plants.
🌑General features of Hornworts
🔴Gametophytic plant body is simple, thallus like dorsiventral without air chambers. Each cell of the thallus possesses a single large chloroplast with a pyrenoid.
🔴Sporophyte is not completely dependent on gametophyte for its nourishment.
🔴It is differentiated into foot seta and capsules. Seta is meristematic. Columella is present in a capsule.
🔴The sporophytes produce spores, which play a key role in reproduction. Hornworts do not have vascular tissue.Thallus has thread-like rhizoids to attach the plant’s substrate.
🔴Rhizoids also absorb water and minerals from the environment. Thallus also has a cyanobacteria called nostoc as a symbiotic association with the hornwort.
🔴Nostoc supplies the hornwort with nitrogen in turn the hornwort supplies Nostoc with carbohydrates produced through photosynthesis.
🔴Hornworts have a life cycle that contains both sexual gametophyte and asexual sporophyte generations. The gametophyte stage is the dominant generation Because it has male sex organ or antheridium and the female sex organ, or archegonium. 🔴Male gamete or antherozoids release from the antheridium and travel through the water and reach the archegonium, where they fertilize the eggs.
🔴Each fertilized egg develops into a diploid embryo that gives rise to sporophyte. Sporophytes produce haploid spores. The spores are released into the environment and form a thallus like gametophyte. 🔴They also exhibit the alternation of generations. For Example - Anthoceros, , Folioceros, Megaceros, , Notothylas etc.
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