Anatomy of Flowering Plants

The correct answer is Option A: Sclereids .

Here's why: Sclereids are a type of sclerenchyma tissue, characterized by their thick, lignified cell walls.

These rigid cells provide structural support and protection.

They are commonly found in the hard, protective layers of nuts and the gritty texture of pear pulp.

Let's break down why the other options are incorrect : Fibres are another type of sclerenchyma tissue, but they are long and slender, providing tensile strength.

While they are present in some plant structures, they are not the primary component of nut shells or pear pulp.

Parenchyma cells are thin-walled and loosely packed, making them suitable for storage and photosynthesis.

They are found throughout plants but don't provide the same level of rigidity as sclereids.

Collenchyma cells have thickened cell walls at the corners, offering flexibility and support to young, growing tissues.

They are not typically found in mature fruit structures.

In summary, the presence of sclereids with their thick, lignified walls explains the hardness of nut shells and the gritty texture of pear pulp.

The maintenance of the pressure gradient in sieve tubes is crucial for the process of translocation of nutrients, primarily sugars, within the phloem of vascular plants.

Among the given options, the correct answer is: Option D Companion cells Companion cells play a vital role in the maintenance of the pressure gradient in sieve tubes.

These cells are closely associated with sieve tube elements to which they are connected by numerous plasmodesmata.

Companion cells assist in maintaining the pressure gradient through the following mechanisms: 1.

Loading and Unloading of Sugars: Companion cells actively transport sugars into and out of the sieve tubes.

This activity creates a concentration gradient, leading to osmosis which in turn generates turgor pressure within the sieve tubes.

This pressure drives the flow of sap from source tissues (where sugars are produced) to sink tissues (where sugars are utilized or stored).

2.

Metabolic Support: Companion cells provide metabolic support to the sieve tube elements, which lack a nucleus and other organelles necessary for their own metabolism, thereby maintaining the functional integrity of the sieve tubes.

Therefore, companion cells are integral in managing the pressure gradient required for efficient phloem transport, making Option D the correct choice.

Radial vascular bundles are present in roots. Monocot roots have polyarch and exarch condition of xylem.

The correct sequence of tissues in the stelar region of the stem showing secondary growth from pith towards cortex is : Primary Xylem Secondary Xylem Secondary Phloem Primary Phloem

The large cells around the vascular bundles of C 4 plants form bundle sheath.

These cells have large number of chloroplasts to perform calvin cycle.

Option B : (B), (C) and (D) only Explanation : Lateral meristems are the meristems that add to the width or girth in a process known as secondary growth.

They are responsible for the secondary growth in plants and are found parallel to the sides of the plants.

1.

Axillary buds (A) are not lateral meristems; they are capable of forming branches or flowers.

2.

Fascicular vascular cambium (B) is a type of lateral meristem.

It contributes to secondary growth and produces secondary vascular tissues.

3.

Interfascicular cambium (C) is also a type of lateral meristem.

It also contributes to secondary growth in the stem.

4.

Cork cambium (D), also called phellogen, is a lateral meristem and it produces the cork, a part of the protective outer layer (periderm) in stems and roots.

5.

Intercalary meristem (E) is not a type of lateral meristem but rather a type of apical meristem located at the base of leaves or internodes on a plant stem, which is involved in primary growth and elongation of the plant.

Therefore, the correct answer is option B : Fascicular vascular cambium (B), Interfascicular cambium (C) and Cork cambium (D) only.

During secondary growth in dicot stem, the cells of medullary rays lie between the vascular bundles become dedifferentiated and give rise to new cambium called interfascicular cambium.

Initiation of lateral roots and vascular cambium during secondary growth takes place in pericycle cells of dicot roots.

Epiblema, endodermis and cortex do not dedifferentiate.

The girdling experiment shows that phloem is the tissue responsible for translocation of food; and that transport takes place in one direction i.e. towards the root.

In gymnosperms only sieve cells and albuminous cells are present but they lack sieve tubes and companion cells.