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39

'Fertilisation is not an obligatory event for fruit production in certain plants'. Explain the statement.

Explanation

Fertilisation is not an obligatory event for fruit production in certain plants. Some fruits are developed from unfertilised ovary called parthenocarpic fruits.

These are seedless fruits, such as pomegranate, grapes, etc. Flowers of these plants are sprayed by a growth hormone that induces fruit development even though fertilisation has not occurred. The ovules of such fruits, however, fail to develop into seeds.

40

In a developing embryo, analyse the consequences if cell divisions are not followed by cell differentiation.

Explanation

Cell divisions increase the number of cells in the developing embryo, while cell differentiation helps group of cells to undergo certain modifications to form specialised tissues and organs to form an organism.

At many stages of embryogenesis, if cell differentiation does not occur, the embryo cannot develop into a new organism. It will only remain as a mass of cells.

41

List the changes observed in an angiosperm flower subsequent to pollination and fertilisation.

Explanation

$$ \text { In an angiosperm flower, the post-fertilisation changes occur as follows } $$

Sepal Fall off
Petal Fall off
Stamen Fall off
Zygote Embryo
Primary endosperm nucleus Endosperm (3n)
Synergid Disintegrate
Antipodals Disintegrate
Ovary Fruit
Ovule Seed
Ovary wall Pericarp (epicarp+mesocarp + endocarp)
Integument Seed coat (testa+tegmen)
Funicle of the ovule Stalk of the seed
Micropyle Seed pore
42

Suggest a possible explanation why the seeds in a pea pod are arranged in a row, whereas those in tomato are scattered in the juicy pulp.

Explanation

In pea, fruit is legume. The pea pod is developed from monocarpellary, unilocular and half superior ovary. At maturity, the fruit splits along the dorsal and ventral sutures and discharge its seeds.

In gynoecium with single carpel, ovules are always attached to the ventral suture. This results in the fruit with marginal placentation. Thus, the seeds are arranged in a row in legume (pea) pod.

In tomato, the fruit is berry. It is fleshy fruit develop from superior or inferior ovary. In this, the margins of the carpels grow inward to the centre of the ovary dividing the central chamber into compartments called locules.

So that, the ovules are arranged radially on the axis, attached by placenta that is called axial placentation. That's the reason the seeds are embedded in the juicy pulp.

43

Draw the sketches of a zoospore and a conidium. Mention two dissimilarities between them and atleast one feature common to both structures.

Explanation

The feature common to zoospores and conidia is that both of these are the asexual reproductive structures, which facilitate the process of reproduction in asexually reproducing organisms.

$$ \text { The two dissimilarities between these (zoospore and conidium) are as follows } $$

Zoospore
(Found usually in Algae)
Conidium
(Found usually in Fungi)
Flagellated
Formed inside a sporangium (endogenously)
Non-flagellated
Formed at the tip of conidiophores (exogenously)