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In which plant will you look for mycorrhiza and coralloid roots? Also, explain what these terms mean.

Mycorrhiza, which is also known as ‘fungus-root’, is a mutually beneficial relationship between a plant root and a fungus. In most cases, the fungus grows within the roots of the plants and helps the plant to absorb water and nutrients, and in return, the plant provides the fungus with food, e.g., Pinus, a Gymnosperm.

Coralloid Roots: These roots are associated with nitrogen-fixing cyanobacteria. In coralloid roots, the nodules are formed in large numbers, giving the roots a coralloid appearance, e.g. Cycas and plants of Leguminosae.

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Safeer PP

How are the male and female gametophytes of pteridophytes and gymnosperms different from each other?

The size of gametophyte of of pteridophytes quite large compare  to gymnosperm's gametophytes. Gametophyte of pteridophytes are photosynthetic in nature while gametophyte of  gymnosperms are are not photosynthetic in nature

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LOKESH JAIN

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 Comment on the lifecycle and nature of a fern prothallus.

Pteridophytes show a haplo-diplontic life cycle.

Formation of spores:
The main plant body is a diploid sporophyte, which contains sporophylls. The plant can be homosporous, or it can be heterosporous, producing haploid smaller microspores and larger megaspores.

Germination:
Germination of spores produces haploid, free-living gametophytes called prothallus. The homosporous ferns give rise to bisexual gametophytes, and heterosporous ferns give rise to separate male and female gametophytes.

Formation of gametes:
The prothallus consists of a haploid male sex organ, antheridia and a female sex organ, archegonia, which give rise to antherozoids and eggs, respectively.

Fertilisation:
Fertilisation occurs with the help of water. The diploid zygote develops into an embryo that finally forms a sporophyte.

Nature of the prothallus:

Fern, which is a type of pteridophyte, reveals a haplo-diplontic state. It bears prothallus in the gametophytic stage. Prothallus is the free-living, multicellular, inconspicuous, haploid, photosynthetic, thalloid gametophyte of pteridophytes. It bears unicellular rhizoids for attachment to the substratum. The requirement for damp and moist places is due to the requirement of water for fertilization.

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Safeer PP

Draw labelled diagrams of the following:

(a) Female and male thallus of a liverwort.

(b) Gametophyte and sporophyte of Funaria.

(c) Alternation of generation in Angiosperm.

 

 (a) Female and male thallus of a liverwort:

(b) Funaria, gametophyte and sporophyte: -

(c) Alternation of generation in Angiosperm:

 

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infoexpert23

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Explain why sexual reproduction in angiosperms is said to take place through double fertilisation and triple fusion. Also, draw a labelled diagram of embryo sac to explain the phenomena.

In the process of double fertilisation in the case of angiosperms; one male gamete fuses with the female gamete, and the second male gamete fuses with the secondary nucleus. This fusion of the male and female gametes results in the outcome of the zygote. The fusion between the second male gamete and the secondary nucleus results in the outcome of the primary endosperm nucleus. Since the occurrences of fusion of two nuclei take place, thus it is called double fertilisation. The following figures show double fertilisation:

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infoexpert23

Lichen is usually cited as an example of ‘symbiosis’ in plants where an algal and a fungal species live together for their mutual benefit. Which of the following will happen if algal and fungal partners are separated from each other?

(a) Both will survive and grow normally and independently of each other.

(b) Algal components will survive while the fungal component will die.

(c) Both will die

(d) The Fungi component will survive while the algal partner will die.

Based on the answer, how do you justify this association as symbiosis?

(c) Both will die.

Explanation: The process of ‘symbiosis’ explains that the plant and the fungus which are growing together depend on each other for nutrients and if they are bound to get separated, they will both die because they are codependent.

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infoexpert23

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With the help of a schematic diagram, describe the haplo-diplontic life cycle pattern of a plant group.

Pteridophytes and Bryophytes both reveal a haplo-diplontic life cycle. The diploid phase is not independent in bryophytes; however, it is independent in the case of pteridophytes. Furthermore, the sporophyte is more clearly visible in the case of pteridophytes than in bryophytes.

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Gametophyte is a dominant phase in the life cycle of a bryophyte. Explain.

The dominant phase in bryophytes is represented by gametophytic plants. The gametophyte is self-reliant, photosynthetic, and erect. Antheridia and archegonia are developed and found on the gametophyte. These male and female organs are multicellular. The Antheridia and Archegonia carry the male and female gametes. The antheridium produces biflagellate antherozoids, while the archegonium produces a single egg. Water helps to carry the antherozoids to the archegonium. The antherozoids flagellate, which gives them the feature to be motile. After the process of fertilisation, the zygote is formed. The zygote develops into a multicellular figure called a sporophyte.

The sporophyte in bryophytes is smaller comparably and is not self-reliant. The sporophyte is attached to the gametophyte and gets its nutrition from the gametophyte. The gametophyte has control over the life cycle of a bryophyte in every phase. The gametophyte is self-independent and photosynthetic. The size of the gametophyte is larger as compared to the sporophyte. Also, the sporophyte is not independent and holds on to the gametophyte for nutrition.

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In which plant will you look for mycorrhiza and coralloid roots? Also, explain what these terms mean.

Mycorrhiza, which is also known as ‘fungus-root’, is a mutually beneficial relationship between a plant root and a fungus. In most cases, the fungus grows within the roots of the plants and helps the plant to absorb water and nutrients, and in return, the plant provides the fungus with food. E.g., Pinus. In some cases, the fungus could be harmful to the plants.

Coralloid Roots: These roots are associated with nitrogen-fixing cyanobacteria. In coralloid roots, the nodules are formed in large numbers, in the roots giving them a coralloid appearance. E.g. Cycas and plants of Leguminosae.

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infoexpert23

Comment on the lifecycle and nature of a fern prothallus.

Fern, which is a type of pteridophyte; reveals a haplo-diplontic state. In this situation, both the stages of gametophytic and sporophytic are multicellular. The diploid sporophyte is represented by a prepotent and independent, photosynthetic, vascular plant body. The haploid gametophyte is also independent, but the duration of its life is shorter than that of the sporophytes.
 

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infoexpert23

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