With a neat labelled diagram, describe the parts of a typical angiosperm ovule.
Structure of ovule. Each ovule consists of nucellus surrounded by two integuments and a stalk or funiculus.
(i) Funiculus is stalk-like structure by which ovule is attached to the placenta.
(ii) Hilum. It is the point of attachment of the body of the ovule with the funiculus.
(iii) Raphe. It is the longitudinal ridge formed by lengthwise fusion of funiculus with the body of ovule in a typical anatropous ovule.
(iv) Nucellus. It is a mass of diploid cell called megas-porangium. It provides nourishment in the development of embryo sac.
(v) Embryo sac. It is the female gametophyte which contains the egg apparatus, antipodal and polar nuclei.
(vi) Integuments form seed coats i.e. testa and tegmen.
(vii) Micropyle. It is small opening which is left by the integument in the ovule for the passage of pollen tube into the ovule.
(viii) Chalaza. The basal region of ovule from where the integuments arise is called chalaza.
(vii) Micropyle. It is small opening which is left by the integument in the ovule for the passage of pollen tube into the ovule.
(viii) Chalaza. The basal region of ovule from where the integuments arise is called chalaza.
V.S. of mature ovule to show various parts.
(a) hypocotyl and epicotyl
(b) Coleoptile and coleorhiza
(c) Integument and testa
(d) Perisperm and pericarp.
What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
(a) Draw a diagrammatic sectional view of a mature anatropous ovule and label the following parts in it:
(i) that develops into seed coat.
(ii) that develops into an embryo after fertilization.
(iii) that develops into an endosperm in an albuminous seed.
(iv) through which the pollen tube grains entry into the embryo sac.
(v) that attaches the ovule to the placenta.
(b) Describe the characteristic features of wind pollinated flowers.(a) Explain the different ways apomictic seeds can develop. Give an example of each.
(b) Mention one advantage of apomictic seeds to farmers.
(c) Draw a labelled mature stage of a dicotyledonous embryo.(a) Explain the post-pollination events leading to seed production in angiosperms.
(b) List the different types of pollination depending upon the source of pollen grains.