Question

Compair and contrast the following -xylem and phloem Meridtematic tissue and dermal tissue

Answer 1

PhloemXylemFunctionTransportation of food and nutrients such as sugar and amino acids from leaves to storage organs and growing parts of plant. This movement of substances is called translocation.Water and mineral transport from roots to aerial parts of the plant.MovementBidirectional (Moves up or down the plant's stem from "source to sink")Unidirectional (Moves up the plant's stem)OccurrenceRoots, stems and leaves. transports sucrose to growth (roots and shoots) and storage regions of the plant (seeds fruit and swollen roots)Roots, stems and leavesAdditional FunctionsForms vascular bundles with xylemForms vascular bundles with phloem and gives mechanical strength to plant due to presence of lignin cells. The lignified secondary wall also makes the xylem waterproof and prevent it from collapsing under the pressure of water transpirationStructureElongated, tubular shape with thin walled sieve tubes. The sieve tubes have pores at each end in the cross walls and microtubulesthat extend between sieve elements allowing longitudinal flow of material.Tubular shape with no cross walls which allows a continuous column of water + facilitates more rapid transport within the xylem vessels. There are two types - protoxylem (first formed xylem) + metaxylem (mature xylem) depending on pattern of lignin.ElementsSieve tubes, companion cells, phloem parenchyma (loosely packed resulting in intercellular spaces which allows gas exchange), bast fibers, intermediary cells,Tracheids, vessel elements, xylem parenchyma (loosely packed resulting in intercellular spaces which allows gas exchange), xylem sclerenchymaNature of tissueLiving tissue with little cytoplasm but no nucleus/tonoplast.Dead tissue at maturity so it is hollow with no cell contentsShapePhloem is not star shaped.Xylem is star shaped.Location in vascular bundlePhloem occur on outer side of the vascular bundle.xylem occupy the center of the vascular bundle.It consists of single outermost layer called epidermis which extends over entire surface of plant body. At surface view the cells of the epidermis are irregular in outline but closely fitted together without intercellular spaces. They appear rectangular in transaction. Epidermal cells are parenchymatous in nature with colourless cell sap. In the leaves and young green shoots the epidermis possesses numerous minute openings called stomata.