Advertisements
Advertisements
प्रश्न
Why does self-pollination not lead to seed formation in self-incompatible species?
Advertisements
उत्तर
Self-incompatibility is a gene-physiological event. A single gene, known as the S-gene, regulates incompatibility reactions and contains many alleles. Pollen grains with the S-allele, which is shared by either of the two alleles in pistil cells, won’t work on that pistil. However, any pollen grain that does not share S-alleles with the pistil will function on that plant’s pistil. Self-pollens are unable to fertilize the egg, preventing the formation of an embryo; hence, seeds do not form in self-incompatible species.
APPEARS IN
संबंधित प्रश्न
With the help of a suitable example, explain protandry.
List the different types of pollination depending upon the source of pollen gain.
A flower of tomato plant following the process of sexual reproduction produces 200 viable seeds.
Answer the following questions giving reasons :
(a) What would have been the minimum number of ovules present in pre-pollinated pistil ?
(b) How many microscope mother cells would minimally be required to produce requisite number of pollen grains ?
(c) How many pollen grains must have minimally pollinated the carple ?
(d) How many male gametes would have used to produce these 200 viable seeds ?
(e) How many megaspore mother cells were required in this process ?
Make a list of any three outbreeding devices that flowering plants have developed and explain how they help to encourage cross-pollination.
What is meant by emasculation?
Draw a diagram of a section of a megasporangium of an angiosperm and label funiculus, Micropyle, embryosac and nuclleus.
Compare the characteristic features of insect pollinated and wind pollinated flowers. Explain how the respective features assist in pollination.
Which one of the following is one of the characteristics of self-pollinated flowers?
State the name of the chief pollinating agent against the corresponding plant by choosing from those given in brackets.
Dahlia_______ .
Answer the following question.
Express the process of pollination in Vallisneria.
Differentiate between geitonogamy and xenogamy (allogamy).
Answer the following question.
Write the difference in the characteristics of the progeny produced as a result of the two processes.
What are the adaptations which are required in cross-pollinated
From among the situations given below, choose the one that prevents both autogamy and geitonogamy.
Even in absence of pollinating agents seed-setting is assured in ______.
Feathery stigma occurs in ______.
During Hybridization process anther of the bisexual flower is removed before it dehisces is called ______.
Which of the following floral adapation are adapted by hydrophilous flowers?
Describe any three adaptations in hydrophilous flowers.
Mention any one example of the hydrophilous flower.
What are the major abiotic factors that influence habitat?
Complete the following table:
| Sr. | Type of pollination | Agent | Kind of flower | Examples |
| (i) | ______ | Wind | ______ | Maize |
| (ii) | Chiropterophily | ______ | Dull colour, with strong fragrance, abundant nectar | Adansonia |
| (iii) | Entamophily | Insects | ______ | Rose/Jasmine |
| (iv) | Ornithophily | ______ | Brightly coloured, large and showy. They secrete profuse, dilute n ectar | ______ |
When and why does a plant breeder employ the emasculation technique?
Identify the set of correct statements:
- The flowers of Vallisneria are colourful and produce nectar.
- The flowers of waterlily are not pollinated by water.
- In most of water-pollinated species, the pollen grains are protected from wetting.
- Pollen grains of some hydrophytes are long and ribbon like.
- In some hydrophytes, the pollen grains are carried passively inside water.
Choose the correct answer from the options given below:
Bird pollinated flowers are usually ______.
In sea grass, pollens are long, ribbon like and without exine exhibiting ______ pollination.
What is the definition of pollination?
Which of the following is an abiotic agent of pollination?
Anemophily is the process of pollination by which agent?
Entomophily refers to pollination by which agency?
