Explain the development of the zygote into an embryo and of the primary endospermic nucleus into an endosperm in a fertilised embryo sac of a dicot plant.
Explain the development of the zygote into an embryo and of the primary endospermic nucleus into an endosperm in a fertilised embryo sac of a dicot plant.
Explain the development of the zygote into an embryo and of the primary endospermic nucleus into an endosperm in a fertilised embryo sac of a dicot plant.
Development of endosperm (i) Embryo development occurs after endosperm development in angiosperms. (ii) The three methods of endosperm development are: (a) nuclear type (b) cellular type (c) helobial type (iii) 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. (vii) 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.
Embryo development in dicot plant (i) Embryo formation starts after a certain amount of endosperm is formed. (ii) Zygote divides by mitosis to form a proembryo. (iii) Formation of globular and heart-shaped embryo occurs which finally becomes horse shoe-shaped mature embryo. (iv) In dicot plant, embryo consists of two cotyledons and an embryonal axis between them. (v) The portion of embryonal axis above the level of attachment of cotyledons is epicotyl and terminates in the plumule. (vi) The portion of embryonal axis below the level of attachment of cotyledon is the hypocotyl, it becomes radicle (root tip).
Explain the development of the zygote into an embryo and of the primary endospermic nucleus into an endosperm in a fertilised embryo sac of a dicot plant.
Answers
Jay shri
Development of endosperm
(i) Embryo development occurs after endosperm development in angiosperms.
(ii) The three methods of endosperm development are:
(a) nuclear type (b) cellular type
(c) helobial type
(iii) 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.
(vii) 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.
Embryo development in dicot plant
(i) Embryo formation starts after a certain amount of endosperm is formed.
(ii) Zygote divides by mitosis to form a proembryo.
(iii) Formation of globular and heart-shaped embryo occurs which finally becomes horse shoe-shaped mature embryo.
(iv) In dicot plant, embryo consists of two cotyledons and an embryonal axis between them.
(v) The portion of embryonal axis above the level of attachment of cotyledons is epicotyl and terminates in the plumule.
(vi) The portion of embryonal axis below the level of attachment of cotyledon is the hypocotyl, it becomes radicle (root tip).