Summary TRANSPORT IN PLANTS AND ANIMALS

Transport in Plants and Animals

Transport in Plants and Animals: Introdu

 Transport is the movement of substances within an org
 All living cells require oxygen and food for various met
 These substances must be transported to the cells.
 Metabolic processes in the cells produce excretory pro
eliminated before they accumulate.
 The excretory products should be transported to sites
 Organisms like amoeba are unicellular.
 They have a large surface area to volume ratio.
 The body is in contact with the environment.
 Diffusion is adequate to transport substances across t
within the organism.
 Large multi-cellular organisms have complex structure
from each other hence diffusion alone cannot meet the
and removal of substances.
 Therefore an elaborate transport system is necessary.

Transport in plants

 Simple plants such as mosses and liverworts lack specialized transport system.
 Higher plants have specialized transport systems known as the vascular bundle.
 Xylem transports water and mineral salts.
 Phloem transports dissolved food substances like sugars.

Internal structure of roots and root hairs

The main functions of roots are;

 Anchorage
 Absorption.
 storage
 Gaseous exchange.

 The outermost layer in a root is the piliferous layer.
 This is a special epidermis of young roots whose cells give rise to root hairs.
 Root hairs are microscopic outgrowths of epidermal cells.
 They are found just behind the root tip,
 They are one cell thick for efficient absorption of substances.

,  They are numerous and elongated providing a large surface area for absorption
of water and mineral salts.
 Root hairs penetrate the soil and make close contact with it.
 Below the piliferous layer is the cortex.
 This is made up of loosely packed, thin walled parenchyma cells.
 Water molecules pass through this tissue to reach the vascuiar bundles.
 In some young plant stems, cortex cells contain chloroplasts.
 The endodermis (starch sheath) is a single layer of cells with starch grains.
 The endodermis has a casparian strip which has an impervious deposit
controlling the entry of water and mineral salts into xylem vessels.
 Pericyc1e forms a layer next to the endodermis.
 Next to the pericycle is the vascular tissue.
 In the Dicotyledonous root, xylem forms a star shape in the centre, with phloem
in between the arms.
 It has no pith. In monocotyledonous root, xylem alternates with phloem and there
is a path in the centre

Internal structure of a root hair cell




The main functions of the stem are;

 support and exposure of leaves and flowers to the environment,
 conducting water and mineral salts
 Conducting manufactured food from leaves to other parts of the plant.

 In monocotyledonous stems, vascular bundles are scattered all over the stem,
while in dicotyledonous stems vascular bundles are arranged in a ring.
 Vascular bundles are continuous from root to stems and leaves.
 The epidermis forms a single layer of cells enclosing other tissues.
 The outer walls of the cells have waxy cuticle to prevent excessive loss of water.
 The cortex is a layer next to the epidermis.
 It has collenchyma, parenchyma and schlerenchyma cells.