31 Years NEET Previous Year Questions: Anatomy Of Flowering Plants - 3 - NEET MCQ

The walls of xylem vessels are lignified and bordered pits are common in the walls.

Sapwood is less durable because it is susceptible to attack by pathogen and insects. It is physiologically active and conduction of water takes place through it. Heartwood is not attacked by pathogens and insects as it is physiologically inactive. It is filled with tannins, resins and gums which are not preferred by insects and pathogens.

Abnormal secondary growth occurs in some arborescent monocots (eg. : Dracaena, Yucca)

Bicollateral vascular bundles have phloem in both outer and inner side of xylem. These type of bundles occur in cucurbitaceae.

Quercus suber (Cork oak or Bottle cork) possess cork cells. Cork cells are dead, suberized and impervious to water and air, compactly arranged with no intercellular spaces.

Internally, sieve tubes possess peripheral layer of cytoplasm and are devoid of nucleus. They are living cells. Cell walls of sieve tubes are thickened than surrounding parenchyma cells.

With providing mechanical strength, collenchyma also provides flexibility to the organ and allow their bending eg. : Cucurbita.

Endodermis or innermost layer of cortex has casparian strips in roots. It is called starch sheath in dicot stems. It separate cortex from stele. The cell walls are thickened at the corners in angular collenchyma.

Vascular cambium produces secondary xylem on the inner side and secondary phloem to the outer side.

In monocot leaves, the mesophyll cells are undifferentiated.

In grafting, union between stock and scion produces undifferentiated mass of cells called callus.
Grafting is a method of plant propagation widely used in horticulture, where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially. Grafting is limited to dicots and gymnosperms. Monocots lack the vascular cambium required.

Pericycle in roots is active in the formation of root branches or lateral roots.

Collenchyma is abundant in climbing stems providing mechanical strength.

Collenchyma provides mechanical strength to young dicot stems, petioles and leaves.

Intercalary meristems are derived from apical meristems and separated from the same by permanent cells. They are responsible for localised growth.

Cork cambium and vascular cambium are responsible for secondary growth which increases the girth of the stem.

Ring porous wood is more advanced than diffuse porous wood as it provides for better translocation when requirement of plant is high.

Sieve tubes are elongated tubular conducting channels of phloem. The end walls possess many small pores and have thin cellulosic wall. The lumen is broad in nature.

Commercial fibres are obtained from Cocos nucifera (coconut) also called surface fibres and occur on surface of seeds.

Xylem performs the function of transport of water or sap inside the plant and it is a dead tissue i.e. devoid of protoplasm.

Cells of tunica divide anticlinally to form the outer layer, cells of corpus undergo division in different planes.

The ground tissue in monocot stem do not show distinction into cortex, endodermis, pericycle, pith and pith rays.

Phellogen present in outer cortical cells produces cork or phellem on the outer side which consists of dead and compactly arranged rectangular cells that possess suberised cell walls. Which causes them to become  buoyant. Phellogen also cuts off  cells on innerside called as phelloderm or secondary cortex.

The shoot apex or stem apical meristem has two zones, outer tunica and inner corpus. This theory was given by Schmidt 1924.

Lateral meristems occur on the sides of stem and help in increasing girth of stem and root. It divides only periclinally or radially and is responsible for increase in girth or diameter.