What is self-incompatibility?
The device to prevent inbreeding is self-incompatibility or self-sterlity. This is a genetic mechanism and prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
In case of polyembryony, if an embryo develops from the synergid and another from the nucellus which is haploid and which is diploid?
Fill in the blanks:
(a)Humans reproduce————— (asexually/sexually).
(b)Humans are————— (oviparous, viviparous,ovoviviparous).
(c)Fertilization is————— in humans (external/internal).
(d)Male and female gametes are—————(diploid/haploid).
(e)Zygote is————— (diploid/haploid).
(f)The process of release of ovum from a mature follicle is called————— .
(g)Ovulation is induced by a hormone called—————
(h)The fusion of male and female gametes is called————— .
(i)Fertilization takes place in—————
(j)Zygote divides to form————— which is implanted in uterus.
(k)The structure which provides vascular connection between foetus and uterus is called————— .
If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?
Which is the triploid tissue in a fertilised ovule? How is the triploid condition achieved?
Arrange the following terms in- the correct developmental sequence : Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.
What is the function of the two male gametes produced by each pollen grain in angiosperms?
What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.
Which are the three cells found in a pollen grain when it is shed at the three- celled stage?
Embryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.
The generative cell of a two-celled pollen divides in the pollen tube but not in a three-celled pollen. Give reasons.
Name the parts of anangiosperm flower in which development of male and female gametophytes take place.
Why does the zygote begin to divide only after the division of Primary Endosperm Cell (PEC)?
Can an unfertilised, apomictic embryo sac give rise to a diploid embryo? If yes, then how?
Starting with the zygote, draw the diagrams of the different stages of embryo development in a dicot.
Does self-incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.
In the figure given below, label the following parts: male gametes, egg cell, polar nuclei, synergid and pollen tube
What is meant by emasculation? When and why does a plant breeder employ this technique?
What b triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
Given below are the events that are observed in an artificial hybridization programme. Arrange them in the correct sequential order in which they are followed in the hybridisation programme.
(a) Re-bagging, (b) Selection of parents, (c) Bagging, (d) Dusting the pollen on stigma, (e) Emasculation, (f) Collection of pollen from male parent.
List three strategies that a bisexual chasmogamous flower can evolve to prevent self-pollination (autogamy).
Differentiate between:
(a)hy pocotyl and epicotyl;
(b)coleoptile and coleorrhiza;
(c)integument and testa;
(d)perisperm and pericarp.
Draw the diagram of a mature embryo sac and show its 8-nucleate, 7-celled nature. Show the following parts: antipodals, synergids, egg, central cell, polar nuclei.
In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of egg apparatus.
Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?
With a neat diagram explain the 7-celled, 8- nucleate nature of the female gametophyte.
Draw the diagram of a microsporangium and label its wall layers. Write briefly on the role of the endothecium.
