Chapter -02 Question Answer Part -02

7.Explain the structure of Megasporangium? 


• The ovule is a small structure attached to the placenta by means of a stalk called funicle. 

• The body of the ovule fuses with funicle in the region called hilum. 

Thus, hilum represents the junction between ovule and funicle. 

•  Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyles organised.  

• Opposite the micropylar end, is the chalaza, representing the basal part of the ovule. 

• Enclosed within the integuments is a mass of cells called the nucellus. 

• Cells of the nucellus have abundant reserve food materials. Located in the nucellus is the embryo sac or female gametophyte. 

• An ovule generally has a single embryo sac formed from a megaspore. 

8.  Explain  the process of Megasporogenisis?  

• The process of formation of megaspores from the megaspore mother cell is called megasporogenesis. 

•  Ovules generally differentiate a single megaspore mother cell (MMC) in the micropylar regionof the nucellus. It is a large cell containing dense cytoplasm and a prominent nucleus. 

•  The MMC undergoes meiotic division. 

•  Meiosis results in the production of four megaspores. 

9.What is mean by pollination            

Pollination is the mechanism to achieve this objective. Transfer of pollen grains (shed from the anther) to the stigma of a pistil is termed pollination. 

10. What are the different types of pollination? 

1.Autogamy : In this type, pollination is achieved within the same flower. Transfer of pollen grains from the anther to the stigma of the same flower . In a normal flower which opens and exposes the anthers and the stigma. 

2.Geitonogamy – Transfer of pollen grains from the anther to the stigma of another flower of the same plant.  

3.Xenogamy – Transfer of pollen grains from anther to the stigma of a different plant. This is the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma. 

11. Write a difference Structure of dicot embryo and monocot embryo


Dicot embryo

Monocot embryo

 A typical dicotyledonous embryo , consists of an embryonal axis and two cotyledons.

Embryos of monocotyledons  possess only

one cotyledon.

The portion of

embryonal axis above the level of cotyledons is the epicotyl,

which terminates with the plumule or stem tip.

 At its lower end, the embryonal axis has the

radical and root cap enclosed in an undifferentiated sheath called


The cylindrical

portion below the level of cotyledons is hypocotyl that

terminates at its lower end in the radicle or root tip.

The portion of the embryonal axis above the level of

Attachment of scutellum is the epicotyl

The root tip is covered with a root cap.

. Epicotyl has a shoot apex and a

few leaf primordia enclosed in a hollow foliar structure, the coleoptile.


12 . What is mean by dormancy                         

A)-As the seed matures, its water content is reduced and seeds become relatively dry (10-15 per cent moisture by mass). The general metabolic activity of the embryo slows down. The embryo may enter a state of inactivity called dormancy. 

13.what is apomixis ?                     

A)-a few flowering plants such as some species of Asteraceae and grasses, have evolved a special mechanism, to produce seeds without fertilisation, called apomixis. 

14. What is polyembryony                    

A)-Occurrence of more than one embryo in a seed is referred to as polyembryony.