Post-Fertilisation: Structures & Events

1 Mark Questions

1.Banana is a true fruit but is also a parthenocarpic fruit. Give reason.[Foreign 2010]

Ans. The fruit of banana is formed from the ovary, so it is a true fruit. It is a parthenocarpic fruit because the ovary develops into fruit without fertilisation and is thus, seedless.

1. Why is apple referred to as a false fruit? [HOTS; All India 2010 C] Ans. In apple, the thalamus also contributes to fruit formation. So, apples are called false fruits.
2. Name the mechanism responsible for the formation of seed without fertilisation in angiosperms. Give an example of a species of flowering plants with such seed formation. [Delhi 2010]

Ans. Apomixis is the mechanism responsible for the formation of seeds without fertilisation in angiosperms, e.g. grasses.

1. Name the part of flower that contributes to fruit formation in strawberry and guava respectively.[All India 2009 C]

Ans.(i)In strawberry, the fruit develops from the ovary, other floral parts degenerate and fall off. Thalamus also contributes to fruit formation. (ii)In guava, the wall of ovary develops into the wall of fruit called pericarp.

2 Marks Questions

5.List the post-fertilisation events in angiosperms. [Delhi 2014]

Ans. The post-fertilisation events in angiosperms include: (i)Endosperm and embryo development.

1. Maturation of ovule into seed.
2. Maturation of ovary into fruit

6.Some angiosperm seeds are said to be 'albuminous', whereas few others are said to have a perisperm, Explain each with the help of an example. [Foreign 2012]

Ans. Some angiospermic seeds are albuminous as they retain endosperm even after embryo development, i.e. not completely consumed by embryo, e.g. wheat, maize, castor. While in some angiospermic seeds remnants of nucellus are persistent which is referred to as perisperm, e.g. black pepper and beet.

7.Draw a labelled diagram of a matured embryo of a dicotyledonous plant.[All India 2014 C] Ans. The labelled diagram of a mature embryo of a dicotyledonous plant is as given below.

Plumule

Cotyledons

Hypocotyl

Radicle Root cap

A typical dicot embryo

8.Differentiate between albuminous and non-albuminous seeds, giving one example of each. [Delhi 2011]

Ans. Difference between albuminous and non-albuminous seeds are:

Albuminous seed Non-albuminous seed Endosperm is not Endosperm is completely completely used by used by the developing the developing embryo before the embryo, so a portion maturation of seed, so of it remains in the there is no endosperm seed. left in the seed. Examples coconut, Examples pea, bean and castor and maize. mustard.

9.Banana is a parthenocarpic fruit, whereas oranges show polyembryony. How are they different from each other with respect to seeds? [hots; Delhi 2009]

Ans. Since, banana is a parthenocarpic fruit, it is seedless, whereas oranges show polyembryony that leads to formation of many seeds

1. Name the cell from which the endosperm of coconut develops. Give the characteristic features of endosperm of coconut. [Delhi 2009]

Ans. In opconut, cell formation occurs and the endosperm becomes cellular. The number of free nuclei formed before cellularisation varies greatly. The coconut water is free nuclear endosperm. It is made up of thousands of nuclei and the surrounding white kernel is the cellular endosperm.

1. Name the blank spaces A, B, C and D from the table given below.

Item What it represents in the plant Pericarp Α В Cotyledon in seeds of grass family Embryonal axis С ............. D Remains of nucellus in a seed

Ans.A — Fruit wall, B — Scutellum

1. Plumule and radicle, D — Perisperm

3 Marks Questions

12.Describe endosperm development in angiosperm. [Foreign 2014]

Ans.(i)Embryo development occurs after endosperm development in angiosperms.

1. The three methods of endosperm development are:

(a)nuclear type (b) cellular type

(c)helobial type

1. Nuclear type is the common method in which triploid Primary Endosperm Nucleus (PEN)

undergoes repeated mitotic division without cytokinesis. This stage is called free-nuclear endosperm.

(iv)Cell wall formation starts from the periphery and the endosperm becomes completely cellular, e.g. coconut, rice, etc.

(v)Cells of the endosperm store food materials.

(vi)Endosperm may be completely utilised by the developing embryo before the maturation of seeds as in pea, bean, mustard, etc. These seeds are called non-albuminous or endospermic seeds.

1. In seeds like castor, maize, coconut, rice, etc., a portion of it may remain in the mature

seeds, such seeds are called albuminous or endospermic seeds