Anatomy of Flowering Plants Test - 82

Monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as endarch. 

Vascular bundles of dicot root are described as radial. There are four to six bundles each of xylem and phloem occurring alternately. Xylem is described as exarch. Pith is absent in the older root. Secondary growth is present in dicots and absent in monocots. Thus, option C is correct.

Dicot stem hypodermis is a region lying immediately below the epidermis. It is represented by a few layers of collenchyma cells with angular thickenings. The cells are compactly arranged without any intercellular spaces. Hypodermis provides mechanical support and additional protection. 

In a monocotyledenous stem, the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species. As in the dicots the xylem of the bundles is pre-orientated toward the middles of the stem. Maize is a monocot. So, the vascular bundles in maize stem are scattered in ground tissue. 

When the phloem surrounds the xylem tissue completely. The vascular bundle is known as an amphicribal vascular bundle or an androcentric type. Such vascular bundles are possible in pteridophytes.

In the Concentric bundle, xylem either encircles or is encircled by the phloem. Accordingly, the Amphivasal bundle is a vascular bundle in which xylem encircles the central strand of phloem and it is called amphivasal bundle or leptocentric bundle.

In the conjoint, these vascular bundles xylem and phloem are present on the same radii.

A collateral arrangement is having xylem and phloem next to each other.

So, the correct answer is 'Concentric leptocentric/amphivasal.

The correct option is B.

Cocos nucifera, the coconut palm, is a monocot perennial member of the Arecaceae (palm family), cultivated in tropical areas worldwide for its fruit and fiber. Coir is a natural fibre extracted from the husk of coconut and used in products such as floor mats, doormats, brushes, mattresses, etc. Coir is the fibrous material found between the hard, internal shell and the outer coat of a coconut. Other uses of brown coir are in upholstery padding, sacking and horticulture. Thus, option A is correct. 

Dicot stem vascular bundles are eight in number, arranged in form of a broken ring. The vascular bundles are conjoint, collateral and open. Xylem is on the inner surface and phloem on the outer surface. Xylem is described as endarch. 

Cork is an impermeable, buoyant material, a prime-subset of bark tissue that is harvested for commercial use primarily from Quercus suber (the cork oak), which is endemic to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance and because of its impermeable, buoyant, elastic and fire retardant properties, it is used in a variety of products, the most common of which is for wine stoppers. Cork's elasticity combined with its near-impermeability makes it suitable as a material for bottle stoppers, especially for wine bottles.
Cork stoppers represent about 60% of all cork based production. So, cork is an excellent material for making bottle stopper because it is air tight and not because of cheap, light or easily available. 
Thus, the correct answer is option C.

Stoma (plural stomata) is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening. Stomata is absent in cork or phellem. A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases. Cork contains lenticels. Thus, option A is correct. 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. 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. Sieve tube elements lacks nuclei. Quiescent zone is present in root apex.