Plant Embrogenesis

7/28/2019 Plant Embrogenesis

1/14

Plant embryog


2/14

Process that produces a plant embryofrom a fertilised ovule by asymmetric cell

division and the differentiation ofundifferentiated cells into tissues.

Single-celled zygote undergoes a

programmed pattern of cell division

resulting in a mature embryo Occurs naturally as a result of sexual

fertilization and the formation of

the zygotic embryos.

Divided up into two phases, the firstinvolves morphogenetic events & second

phase, or postembryonic development,

involves the maturation of cells.
http://en.wikipedia.org/wiki/Zygotehttp://en.wikipedia.org/wiki/Zygotehttp://en.wikipedia.org/wiki/Morphogenesishttp://en.wikipedia.org/wiki/Morphogenesishttp://en.wikipedia.org/wiki/Zygotehttp://en.wikipedia.org/wiki/Zygote


3/14

seed formation andgermination


4/14

flower

Nectar


5/14

FLOWERING PLANT LIFE

CYCLE

Divided into Haploid & Diploid

generations.

Haploid generation begins after meiosis

with spores that undergo mitosis &

differentiate into either a pollen grain or

an embryo sac.

Diploid generation begins after

fertilisation with the zygote & forms the

mature plant with vegetative organs.


6/14


7/14

FERTILIZATIONsperm cell (n) + egg cell (n) ZYGOTE (2n)

EMBRYOTRIPLE FUSION:

sperm cell (n) + polar nuclei (2n)ENDOSPERM NUCLEUS (3n)


8/14

TWO FERTILISATION EVENTS OCCUR IN

FLOWERING PLANTS

One sperm unites with the egg cell to formzygote & initiate embryogenesis.

Second unites with a specialised cell withinthe embryo sac to initiate the differentiationof endosperm which is a triploid tissue.

Endosperm is present during seeddevelopment & provide nutrient to theembryo, the germintaing seedling or both.

Fertilisation also causes the ovule todevelop into a seed & ovary to differentiateinto fruit.


9/14


10/14

Embryo DevelopmentZygote (within the embryo sac)

First Division

Upper cell Lower cell

Proembryo Basal cell of the Suspensor

Mass of cells Suspensor Stalk

(surrounded by endosperm) Suspends embryo into endosperm

Proembryo, divided into 3 layers

Protoderm ---> Surface Tissues

Procambium ---> Vascular Tissues

Ground Meristem ---> Ground Tissues

The embr o takes on the sha e of an axis with meristems at both ends


11/14

PRIMARY ORGAN SYSTEMS IN A MATURE

EMBRYO

The AXIS & the COTYLENDON

Both are composed of 3 tissue layersprotoderm, procambium & groundmeristem.

These will develop in epidermal, vascular &parenchyma tissue of the young seedling.

Axis region contain the root & the shootmeristem.

Cotylendon is terminally differentiatedorgan that accumulates food reserves thatare utilised by the seedling for growth.


12/14

EMBRYO DEVELOPMENT The first division of the zygote produces a small proembryo cell and

a larger basal cell that develops the stalked suspensor, which

elevates the developing Proembryo into the endosperm tissue.

The embryo meristems are the apical shoot meristem and the apical

root meristem, from which structures of the shoot system and root

system will ultimately develop.

The cotyledons rapidly elongate, and the embryo is divided intoregions, with respect to the cotyledons.

The region above the attachment of the cotyledons is the epicotyl,

which contains the apical shoot meristem

The region below the attachment of the cotyledons is the hypocotyl

that ends with the rradicle, containing the apical root meristem. Typically the embryonic axis will have to fold, to fit within the embryo

sac

Endosperm may or may not be absorbed into the cotyledons. It may

be consumed completely in the maturation of the embryo, or some

may remain for germination.


13/14

EMBRYOGENESIS IN HIGHER PLANT

THEREFORE SERVES.

To specify meristem & root-shoot plant

body pattern.

To differentiate the primary plant tissue

types.

To generate a specialised storage organ

essential for seed germination.

To enable the sporophyte to lie dormantuntil the conditions are favourable for

postembryonic development.


14/14

Plant Embrogenesis

Documents

Transcript of Plant Embrogenesis