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Select the correct pair. [NEET 2021]
The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium.
Identify the incorrect statement. [NEET 2020]
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.
Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following. [NEET 2019]
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.
Secondary xylem and phloem in dicot stem are produced by [NEET 2018]
The vascular cambium normally gives rise to [NEET 2017]
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.
As compared to a dicot root, a monocot root has
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 are also called soft wood spermatophytes because they lack :
Gymnosperms lack xylem fibres. Large amount of parenchymatous cells are present with secondary xylem tracheids. So, these are also known as softwood spermatophytes.
Water containing cavities in vascular bundles are found in :
Stem of maize has water containing cavities in vascular bundles.
Closed vascular bundles lack
In closed vascular bundle cambium is absent between xylem and phloem.
Companion cells are closely associated with :
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 a product of :
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
In Kranz anatomy, the bundle sheath cells have thick wall, no intracellular spaces and large number of chloroplasts.
Some vascular bundles are described as open because these
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 cells is
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.
Which one of the following is wrongly matched?
Smut is a disease of cereals, corn, grasses and sorghum caused by many species of fungi.
The cork cambium, cork and secondary cortex are collectively called:
Phellem, phellogen and phelloderm are collectively called periderm.
In land plants, the guard cells differ from other epidermal cells in having :
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
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:
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.
Which one of the following is not a lateral meristem?
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).
The chief water conducting elements of xylem in gymnosperms are:
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:
Reduction in vascular tissue, mechanical tissue and cuticle is characteristic of hydrophytes.
In barley stem vascular bundles are:
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:
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:
Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by
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:
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
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.
Which one of the following is resistant to enzyme action?
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.
Passage cells are thin-walled cells found in______.