31 Years NEET Previous Year Questions: Anatomy of Flowering Plants - 1 - NEET MCQ

The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium.

In a large tree, only the outer secondary xylem (sapwood) serves in water conduction, while the inner part (heartwood) is composed of dead but structurally strong secondary xylem and is darker in colour due to the deposition of tannins, resins and oils.

In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells. When the bulliform cells in the leaves have absorbed water and arc turgid, the leaf surface is exposed. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss.

• Vascular cambium is a type of lateral meristem that produces secondary tissues (xylem and phloem) during secondary growth. 
• It is produced by two types of meristem: intrafascicular cambium (primary meristem occurring as strip in vascular bundles) and interfascicular cambium (secondary meristem which develops from permanent cells of medullary rays which occur at the level of intrafascicular strips).
• The cells of vascular cambium are of two types : fusiform initials which produce secondary xylem towards outside and secondary phloem towards inner side and ray initials which give rise to vascular rays.

Cells of vascular cambium divide periclinal both on the outer and inner sides to form secondary permanent tissues, i.e., secondary xylem and secondary phloem.

The vascular bundles are arranged in a loose circle inside the endodermis of a monocot root. In a monocot root, more than six vascular bundles are present. It shows polyarch condition.

 Gymnosperms lack xylem fibres. Large amount of parenchymatous cells are present with secondary xylem tracheids. So, these are also known as softwood spermatophytes.

Stem of maize has water containing cavities  in vascular bundles.

In closed vascular bundle cambium is absent between xylem and phloem.

Companion cells are narrow, elongated and thin walled living cells. They lie on the sides of the  sieve tubes and are closely associated with them through compound plasmodesmata. It is supposed that the nuclei of the companion cells control the activities of the sieve tube through plasmodesmata. Companion cells also help in maintaining a proper pressure gradient in the sieve tube elements.

The common bottle cork is the product of phellogen. Phellogen produces cork or phellem on the outer side. It consists of dead and compactly arranged rectangular cells that possess suberised cells walls. The cork cells contain tannins. Hence, they appear brown or dark brown in colour.

In Kranz anatomy, the bundle sheath cells have thick wall, no intracellular spaces and large number of chloroplasts.

Open means presence of cambium during secondary growth. Vascular cambium divides to form secondary xylem towards inner side while secondary phloem towards outside.

Function of companion cell is to load sugar and amino acids into sieve elements. These cells use transmembrane proteins to take up by active transport.

Smut is a disease of cereals, corn, grasses and sorghum caused by many species of fungi.

Phellem, phellogen and phelloderm are collectively called periderm.

Guard cells differ from epidermal cells in having chloroplast. The cell wall of guard cells are not uniform, inner walls are thicker than the outer walls, epidermal cells are uniformly thin.

Ground tissue includes all tissues except epidermis and vascular bundles. The ground tissue comprises the bulk of the primary plant body. Parenchyma, collenchyma and sclerenchyma cells are common in the ground tissue.

Heartwood differs from sapwood in having dead and non-conducting elements. In old trees, the inner region that comprises dead elements with highly lignified walls is called heartwood. Heartwood does not conduct water but gives mechanical support to the stem. On the other hand, the peripheral region, which is lighter in colour are called sapwood. It is involved in the conduction of water and minerals from root to leaf.

Meristem is divided on the basis of position in plant bodies into apical meristem, lateral meristem and intercalary meristem. Lateral meristem is present on the lateral sides, that is fascicular and interfascicular cambium and cork cambium (phellogen).

Tracheids are chief water conducting elements of xylem in gymnosperms. They are devoid of protoplasm and hence dead. The wall constituting the tracheids is hard, thick and lignified. These are elongated cells with tapering ends.

Reduction in vascular tissue, mechanical tissue and cuticle is characteristic of hydrophytes.

In barley stem vascular bundles are closed and scattered. They are open only for a hours in the day time and never open at night. e.g Cereals.

Palisade parenchyma is absent in leaves of Sorghum. It is a leaf tissue composed of columnar cells containing numerous chloroplasts in which the long axis of each cell is perpendicular to the leaf surface. The palisade parenchyma is usually directly beneath the epidermis of the upper surface of the leaf. The cells of the palisade parenchyma are cylindrical. Neighbouring cells look like the stakes of a palisade. Cells of the palisade parenchyma contain three to five times as many chloroplasts as those of the spongy parenchyma. The chloroplasts stay usually near the cell’s wall, since this adjustment guarantees optimal use of light.

The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is maturing.​​​​​​This is the time when protoxylem develops or produces annular and spiral thick carrier elements. They also grow plants to provide mechanical support.

Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by position of protoxylem. In dicot root the protoxylem is located near the periphery of the vascular cylinder while in dicot stem the protoxylem is located near the centre of vascular bundle i.e. the xylem is endarch.

Vascular tissues in flowering plants develop from plerome. Plerome is a central core of primary meristem which gives rise to all cells of the stele from the pericycle inward. 

The length of different internodes in a culm of sugarcane is variable because of intercalary meristem. Intercalary meristem is not a part of apical meristem, occurs in the internodes of grasses (sugarcane) between leaf nodes and enables longitudinal growth of the stem.

Pollen exine is resistant to enzyme action. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzymes that degrades sporopollenin is so far known. 

• The endodermis is the central, innermost layer of cortex in some land plants.
• It is made of compact living cells surrounded by an outer ring of endodermal cells, that are impregnated with hydrophobic substances to restrict the apoplastic flow of water to the inside.  
• Passage cells are endodermal cells of older roots, which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside from cortex to pericycle.