Roots

Lateral root

a branch root that forms endogenously (from within the root itself). these roots come from the pericycle, and bore through the endodermis, cortex, and epidermis in order to reach soil.

Aerial roots

roots that are modified to absorb water and ions out of the air rather than from the ground. these are sometimes photosynthetic, and often found in epiphytes: nonparasitic plants that grow on other plants.

Storage roots

roots that function to store starch. primary roots have a large cortex and store starch. Secondary roots have little conducting tissue and thus are ideal for the large numbers of storage parenchyma found in them. ex carrots, radishes.

Prop roots

roots that grow out of a stem and function to keep a plant upright. they are a type of adventitious root.

Adventitious roots

roots that grow out of a stem rather than another root. these include prop roots.

Root regions

rthe four zones of primary root growth. root cap +mucigel, region of cell division, region of cell elongation, region of maturation+root hairs

Velamen

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Fibrous root system

A root system in which lateral and adventitious roots form a dense network of shallow, soil-bound roots that do not undergo secondary growth. large root surface area. found in monocots (grasses)

Root functions

Primary: anchoring of the plant in soil, absorbing water and ions. Secondary: storage of starch and conduction of water.

Primary growth in roots

a continuous process of elongation of the roots carried out by the apical meristem. The region of actively dividing cells is called the zone of division. The zone of elongation is actually responsible for growth in length of the root. A root cap of parenchymal cells that secrete protective mucigel in order to lubricate the tip of the root is also present.

Mucigel

a highly hydrated polysaccharide produced by the root cap that lubricates the root tip as it passes through soil. also known as mucilage,

Root cap

a mass of living parenchymal cells that protect the apical meristem and aids in root penetration of the soil by secreting mucigel, a lubricant. It is also responsible for orienting the plant as to which way is down.

Vascular cylinder

a region of the root within the endodermis that is made up of three regions (from outermost to innermost): -pericycle: -primary phloem -primary xylem

Zone of elongation

a region proximal to the zone of cell dvision, only about a few millimeters in length. cells in tis region elongate, which accounts for the lengthening of roots.

Suberin

a waxy substance found in Casparian strips whose function is to repel water.

Cortex

ground tissue iof parenchyma in a stem or root, surrounded externally by the epidermis and internally by the vascular cylinder. it has prominent amyloplasts for starch storage, intercellular spaces for gas exchange, and an endodermis to make water flow into the vascular cylinder.

Taproot system

in this type of root system, long primary roots grow deep and can form branch roots and undergo secondary growth. often found in dicots.

Casparian Strips

strips of suberin, a waxy substance, that are located along the top, bottom, and sides of cells that line up in order to create a water-proof seal. they blocj apoplastic water flow and force water to go instead through plasmalemma. Found in the endodermis.

Apoplastic movement

the flow of water through intercellular spacess and along the primary cell walls. The water does not cross a membrane.

Endodermis

the innermost layer of the cortex, made of densely packed parenchymal cells, that have a casparian strip. it functions to direct water flow into the vascular bundle.

Pericycle

the nonvascular portion of the vascular cylinder.it is composed of layers of parenchyma cells. -gives rise to -more pericycle - lateral roots. -cork cambium and periderm. -contributes to the vascular cambium when plants undergo 2ndary grwth

Epidermis

the outermost layer of cells of the primary plant body. it provides mechanical protection, minimizes water loss, and controls gas exchange. in the root its function is to absorb minerals and water, and therefore has little to no cuticle and many root hairs to incread absorptive surface.

Zone of division

the region of actively dividing cell sin a root. proximal to the root tip.

Zone of maturation

the region proximal to the zone of elongation. cells in the area have reached maturity and have become differentiated. root hairs are often found in this region, and it is thus sometimes called the root hair zone.

Root hairs

tubular extensions of the epidermal cells that greatly increase the absorptive surface of the root. the are found in the zone of maturation.

Symplastic movement

water movement from cell to cell through the plasmodesmata. the water must cross a membrane in this type of movement.

Transcellular movement

water movement through vacuoles cell membranes, and cell walls. athe water must cross a cell membrane in this type of h2o movement.