Test: Anatomy of Flowering Plants - 1

The parenchyma is widely distributed in plant bodies such as stems, roots, leaves, flowers, and fruits.

The parenchyma tissue is found in the soft parts of the plants such as the cortex of roots, ground tissue in stems & mesophyll of leaves.

They function in storage, photosynthesis, and the bulk of ground and vascular tissues.

It is also distributed in the pith, medullary rays & packing tissue in the xylem and phloem.

Trapa < Nicotiana < Pisum < Castanea

Reticulate venation is a characteristic in Dicotyledonous leaves. In reticulate venation, veins are interconnected and form a web-like network. There is a prominent vein called the midrib from which many small veins arise which finally form a net-like structure in the lamina. The veins vary in thickness in the reticulate venation of the dicot leaves.

Vascular bundles in which cambium is present between xylem and phloem are called open vascular bundles and those in which cambium is absent are called closed vascular bundles.

Both apical meristems and intercalary meristems are primary meristems because they appear early in life of a plant and contribute to the formation of the primary plant body.

Fig: Longitudinal section of shoot apex showing location of meristems and young leaves

In angiosperms, vascular tissue develops from the plerome.
Plerome is the primary meristem that forms the central core of a plant or plant part which gives rise to the stele (includes the vascular tissue, pith and pericycle). The part of plerome from which vascular tissues are formed is called procambium.

Secondary growth occurs in most seed plants, but monocots usually lack secondary growth. If they do have secondary growth, it differs from the typical pattern of other seed plants. The formation of secondary vascular tissues from the cambium is a characteristic feature of dicotyledons and gymnosperms.

• Tracheids are the chief water-conducting elements in gymnosperms and seedless vascular plants. They can also be found in angiosperms. They are elongated cells, closed at both ends.
• Vascular element, found in angiosperms, is the vessel element that are joined end to end to form vessels in which water flows unimpeded, as in a pipe.

Sclerenchyma is lignified supportive simple permanent tissue composed of thick walled and dead cells as the living protoplast is absent in the cells. They are generally hard and found in rough fruits and stem.

The stomata are more numerous over the abaxial (lower) epidermis of the leaf than the adaxial (upper) epidermis.

Exceptions:

• Floating leaves where most or all stomata are on the upper surface.
• Vertical leaves, such as those of many grasses, often have roughly equal numbers of stomata on both surfaces. 

In isobilateral leaves of monocot, certain adaxial epidermal cells along the veins modify themselves into large sized, thin walled, empty, colourless cells. These are called bulliform cells.

Exarch xylem is the arrangement in which the protoxylem (the first formed primary xylem cells in a plant shoot/root) is directed towards the periphery and metaxylem (later formed primary xylem cells in a plant shoot/root) is directed towards the centre. Its development follows a centripetal pattern and is characteristic of roots. 

Thus the correct answer is option D.

The parenchymatous cells which lie between the xylem and the phloem are conjunctive tissue. It is concerned with the formation of vascular cambium and storage of food and water.

Jute is an agricultural product and chemically known as lignocellulosic fiber.
The ultimate cells of individual fibers are formed by the alpha-cellulose whereas the presence of hemicellulose and lignin cements the ultimate fibers.

Jute is mainly composed of polysaccharides and lignin, but it also contains a smaller amount of fats and waxes, pectin, nitrogenous, coloring and inorganic matters. 

It is the anatomy of monocotyledonous roots.

In the arborescent monocot stem, secondary cambium grows in the hypodermal region for secondary growth that increases the girth of the stem.

The companion cells are specialized parenchymatous cells, which are closely associated with sieve tube elements.
The sieve tube elements and companion cells are connected by pit fields present between their common longitudinal walls.

Companion cells help in maintaining the pressure gradient in the sieve tube.

In monocotyledons, the guard cell of stomata are dumb-bell shaped, thicker on top and bottom and thinner in the middle.

Tunica-Corpus Theory: Schmidt in 1924 postulated tunica- corpus theory on the basis of studies of shoot apices of angiosperm.

This theory is concerned with planes of cell division in the apex. In contrast to apical cell theory and histogen theory, tunica-corpus theory is applicable only to shoot apex and not to root.

This theory divides the region (shoot apex) into two tissue zones known as tunica and corpus.

The shoot apex is composed of two layers of cells of tunica and corpus  (layer L1, L2 and L3 to denote the outer layer of tunica, the inner layer of tunica and corpus respectively).

The plasmodesmata connections exist between the cells of tunica and corpus.

The vascular bundle shown in the figure is closed and conjoint as cambium is absent between xylem and phloem tissue.

Plants have different kinds of meristems. The meristems which occur at the tips of roots and shoots and produce primary tissues are called apical meristem.

The endodermis forms the outermost layer of vascular bundles. Anything entering inside the plant body must cross the endodermis to be transported via xylem and phloem.
Thus, endodermis is called a biological check post of the cell.

Grasses belong to monocotyledonous angiosperms in which secondary growth does not occur. Plants elongate by the activity of both apical and intercalary meristem.

In dicot stems, the cells of cambium present between primary xylem and primary phloem is intrafascicular cambium.

A tissue is a group of cells having a common origin and usually performing a common function.