Anatomy of Flowering Plants

In monocotyledons the seeds are generally endospermous.

The internal structure of grain can be studied in a longitudinal section.

It shows two distinct regions upper large region, the endosperm and lower smaller region, the embryo.

The endosperm is surrounded by a special one cell thick layer, called aleurone layer.

It is filled with aleurone grains which are proteinaceous in nature.

Other components of this layer are phytin, carbohydrates and small amounts of phospholipids are also present.

In most of the gymnosperms, like conifers and cycads, vessels are absent and the wood is made entirely of tracheids.

Such wood is known as nonporous.

In angiosperms, on the other hand, the wood consists of both tracheids and vessels.

The wide vessels appear as pores between otherwise small sized tracheary elements.

Such a wood is known as porous.

In porous wood, if vessels have essentially equal diameters and are uniformly distributed throughout the ring, the wood is known as diffuse porous.

It is characteristic of plants growing in tropics.

Chlorenchyma cells are those parenchymatous cell which contain chloroplast in them.

They are capable of photosynthesis.

A spore capsule of moss can perform photosynthesis, thus chlorenchyma are present in them.

The cells of queiscent centre have lower concentration of DNA, RNA and protein as compared to other cells in the root apex.

These cells do not divide, hence cytoplasm is light and nuclei are small in them.

This concept is based upon quiescent centre theory proposed by Clowes (1961).

Vessels are elongated, multicellular water conducting channels with wide lumen formed by end to end fusion of a large number of vessel elements.

Tracheids are elongated dead cells with tapering ends having lignified walls and large or wide lumen.

Their main function is conduction of water and minerals from root to leaf.

Generally gymnosperms do not have vessels but a few gymnosperms with vessels are Ephedra, Smilax etc.

Most of angiosperms have vessels except of few e.g., Trochodendron.

Apical meristems are situated at the tips of the root and shoot.

They take part in initial growth.

Plants elongate and increase in height as a result of divisions in this meristem.

Promeristem and primary meristem (root and shoot apices) are included in this type of meristem.

When xylem and phloem strands are present at different radii the vascular bundles are radial and 4 radial vascular bundles (tetrach condition) are present in dicot root.

This is called tetrach conditions.

Inulin is a water soluble fructosan.

It is a common reserve food in members of family compositae.

Pectin is a mucopolysaccharides and occur in plant cell walls.

At the time of fruit ripening wall of pectins hydrolyse to give constituent sugars.

In plants during vascularisation, differentiation of procambium occurs followed by the formation of primary phloem and xylem simultaneously.