Is it possible to consider vegetative propagation observed in certain plants like Bryophyllum, water hyacinth, ginger, etc., as a type of asexual reproduction? Give two/three reasons.
The formation of new plants from vegetative units (vegetative propagules) such as buds, tubers, rhizomes. etc., is called vegetative propagation (vegetative reproduction). It can be considered as a type of asexual reproduction as it involves the production of new individuals.
(i) by a single parent
(ii) without the formation and fusion of gametes
(iii) without resulting in any genetic or morphological variations.
'Fertilisation is not an obligatory event for fruit production in certain plants'. Explain the statement.
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.
In a developing embryo, analyse the consequences if cell divisions are not followed by cell differentiation.
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.
List the changes observed in an angiosperm flower subsequent to pollination and fertilisation.
$$ \text { In an angiosperm flower, the post-fertilisation changes occur as follows } $$
| 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 |
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.
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.