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311 Syllabus

The Egg is a Polarized CellEggLab300.jpg (58516 bytes)

The Apical Region contains all the Plastids & the Nucleus.

The Basal Region contains a large Vacuole.

The first cell division is Polar (Asymmetrical)

It produces a small Apical Cell & a Large Basal Cell

The Apical Cell produces most of the Embryo

The Basal Cell Produces the Suspensor and  part of the Root Apical Meristem

This establishes the Axial Pattern of the Embryo and the resulting plant!

Embryo Development in Arabidopsis.

The Zygote undergoes an unequal Cell Division

The Apical Cell produces the Embryo while the Basal Cell produces the Suspensor.

ZygDiv-1Lab300.jpg (44773 bytes)

Once the Apical-Basal Polarity is established, embryos pass through a programmed sequence of events which involve Cell Division, Enlargement and Differentiation.

The first discernable stage of Embryo Development is called GLOBULAR. One of the Three Primary Meristems (Protoderm) is visible at this Stage.

Emb166ColrLab300.jpg (35866 bytes)

Localized growth at the apical end produces Cotyledon Primordia. This is called the HEART Stage.

The Cotyledons and the Axis undergo extensive elongation to produce the TORPEDO Stage.

The Shoot Apical Meristem (SAM) develops between the Cotyledons.

The Root Apical Meristem (RAM) develops at the opposite pole. The Hypocotyl (H) develops from the middle region of the Axis. The Hypophysis contributes to the RAM.

Regions of the adult plant can be traced back to regions of the Embryo.

 EmbGlobLab250.jpg (36715 bytes)

EmbHeart3DLab175.jpg (20744 bytes)
Heart Stage

EmbTorp3DLab200.jpg (28213 bytes)
Torpedo Stage

EMB166Color300.jpg (64855 bytes)
PrimaryMeristems3D300.jpg (40176 bytes) RootXSDiag3D300.jpg (46368 bytes)
There are three Primary Meristems in Plants. These produce the Three Primary Tissues. The Protoderm produces the Epidermis. The Ground Meristem produces Ground Tissues & the Procambium produces Vascular Tissues. These can be seen in cross-sections of the Root and Hypocotyl during Embryo development. This shows a cross section of an embryonic Root. It  has an Epidermis which encloses the Ground Tissues. The Endodermis is the innermost layer of Ground Tissue. The Vascular Tissues are Phloem and Xylem.

Three Essential Features of the Mature Plant are Established during Embryogenesis

The Apical <--> Basal Axial Polarity is fixed.

The Apical & Primary Meristems arise.

The Radial Pattern of the three Primary Tissues is apparent.

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