Tag: biology

Passage cells are endodermal in origin. These are found in cells of older roots which have retained thin walls and casparian strips to allow some symplastic flow to the inside. These do not get suberized or thickened.
Experimental evidence suggests that passage cells function to allow transfer of solutes such as calcium and magnesium into the stele, in order to eventually reach the transpiration system. For the most part, however, old roots seal themselves off at the endodermis and only serve as a passageway for water and minerals taken up by younger roots downstream. So, passage cells occur in endodermis and not in pericycle, cortex or epidermis.
Thus, the correct answer is option C.

Cotton, seed hair fibre of a variety of plants of the genus Gossypium, belonging to the hibiscus, or mallow family (Malvaceae) and native to most subtropical parts of the world. Cotton is a soft, fluffy staple fibre that grows in a boll or protective capsule, around the seeds of cotton plants of the genus Gossypium in the family of Malvaceae.
The fibre is almost pure cellulose. Under natural conditions, the cotton bolls will tend to increase the dispersion of the seeds. The epidermis cells is a single-layered group of cells that covers plants leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. Cotton fibres are collected from epidermal layer of seeds. So, cotton fibres are epidermal hairs of seed and not epidermal hairs of fruits, fibres taken out from roots or fibres taken out from the stem. 
Thus, the correct answer is option B.

The epidermal tissues system forms the outer protective covering of primary plant body in form of epidermis and of secondary plant organs in form of periderm. 

The apical meristematic tissue is continuously dividing tissue which mainly helps forms different specialized cells. Periblem is the histogen in plants that gives rise to the cortex. It does not give rise to the epidermis, pericycle, and the pith. It is the multilayered zone that lies beneath the dermatogen. The periblem cells divide into anticlinal and periclinal planes and give rise to cortex and endodermis. Pleurome gives rise to pericycle, vascular tissues, pith and medullary rays. Dermatogen gives rise to an epidermal layer of plant organs. 
Thus, the correct answer is option B.

The bark is composed of periderm and stem's secondary phloem, the cork cambium, phelloderm and cork cells together make up the periderm. Formation of new periderm layer renders the previous layer dead due to stoppage of water and nutrient supply and differentiates the bark into two regions, namely outer and inner bark. The cork, secondary cortex and phloem present just outside the innermost phellogen constitute outer bark while rest of the tissues present in the outer bark make inner bark. Formation of subsequent periderm layers as overlapping scales gives scaly bark as is present in Psidium. When the bark is peeled off as large sheets, it is termed as intermediate bark as is found in Eucalyptus and Betula.
Thus, the correct answer is option C.

The epidermis cells are the cells which form the outer layer and plays an important role in protection. It helps to prevent the water loss by transpiration. Nerium, is a xerophyte which has layers of epidermal tissue to curtail the rate of transpiration. It is a type of xerophytic adaptation.
Thus, the correct answer is option D.

Prostele is a primitive and simple type of stele. It consists of a solid mass of xylem surrounded by phloem, pericycle, and endodermis. It is permanently present in adult stems of many living pteridophytes, e.g. Lygodium, Lycopodium, Hymemophyllus, and Selaginella. It is present in vascular plants. Protostele is of four types as haplostele, actinostele, plectostele and mixed protostele. Thus, option C is correct.

Laticiferous vessels are the specialized thin walled parenchymatous cells that secrete latex and are found in the cortex. They lack pits and are composed of cellulose and hemicelluloses and serve to secrete latex. Epidermis is the outermost covering of the primary plant body and is mostly represented by a single layer of compactly arranged, barrel-shaped parenchyma cells.
The innermost layer of cortex forms endodermis which has compactly arranged barrel shaped cells. The primary thin walled endodermis shows suberin deposition in form of bands or strips that run around the radial and end walls of the cells and forms casparian strips. Vascular bundle consists of xylem, phloem and cambium (in dicot only) which are derived from procambium and serve in translocation of food and sap.
Thus, the correct answer is option A.

Hypodermis lies below the epidermis. These cells are sometimes modified to give additional structural support or to store food materials or water. Since its cell walls are heavily suberized and impermeable to water its apparent function is to keep the water and nutrients from leaking out through the cortex. The hypodermis is especially well developed in plants of arid regions and in those with shallow root systems. It also deters the entrance of soil microorganisms. So, the function of hypodermis is support and not storage, hardness or protection. Thus, option C is correct.