Types of Root

8/14/2019 Types of Root

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introduction

• Roots are the principal water-absorbing organof a plant.

•

• They are present on essentially all vascularplants.

•

• By definition, a root must have vascular tissues,water conducts in xylem and sugar conductsin phloem, arranged in a particular way.

•

• Much thinner, threadlike rhizoids (means "root-like") are present on the nonvascular plants,such as mosses and liverworts, and ongametophytes of vascular plants without

seeds, such as ferns, horsetails, and clubmosses.





• There are three primary functions of roots:

– to anchor the plant to a substrate,

– to absorb water and dissolvedminerals, and

– to store food reserves.

–

• Typically we see roots in soil, but thereare specialized types of aerial roots(air roots) that enable climbingplants and epiphytes to becomeattached to rocks, bark, and othernon-soil substrates.

• In addition, parasitic plants may form



•

•

To absorb water and dissolved minerals,a young sector of a root commonlypossesses numerous single-celledprojections called root hairs, which

greatly increase the absorbing surfaceof the root and achieve much greatercontact with soil particles.

•

• Water uptake into the young root israpid because there is little resistancethrough the outer cell walls, and ingeneral these walls contain virtually

no water-repellent wax (cutin).



• Both young and old roots can be

important repositories forcarbohydrates, usually in the form of starch grains located in root cortex,

but in addition older roots may storemassive quantities of starch and evenbecome specialized below-groundstorage organs.

•

• Storage of carbohydrates in roots andother below-ground plant organs is an

important plant strategy for surviving



FIBROUS ROOT•

A fibrous root system (sometimesalso called adventitious root system)is the opposite of a taproot system. Itis usually formed by thin, moderatelybranching roots growing from the

stem. A fibrous root system isuniversal in monocotyledonous plantsand ferns, and is also common indicotyledonous plants.

•



• Most trees begin life with a taproot,

but after one to a few years changeto a wide-spreading fibrous rootsystem with mainly horizontalsurface roots and only a fewvertical, deep anchoring roots.

• A typical mature tree 30-50 m tallhas a root system that extends

horizontally in all directions as faras the tree is tall or more, but wellover 95% of the roots are in the top

50 cm depth of soil.



TAP ROOT

• Taproots result when the mainroot growing downward, theprimary root, grows much

larger than the secondaryroots.

• If you have dug up dandelions in

your backyard, you've seentheir taproots

• . In gardens, carrots are even

better taproot examples. Oak,



• At the right you see

the taproot of aseedling WaterOak. The yellowline denotes where

the soil's surfacewas when wepulled the seedlingfrom my garden

soil, so you can seethat, at least in thecase of thisseedling, thetaproot canpenetrate the soil



• How tap root can beneficial to plant?

– allows the plant to reach downquite far to find water to sustainitself. In drier climates, or areaswhere water tends to run deep, this

can be incredibly useful. – Indeed, many desert plants have

incredibly well-developed tap rootsystems, allowing them to survive in

even the most arid of climates.



• Also function as a reservoir forfood and water.

• The tap root can grow very wide,and remain relatively protectedunderground, allowing the

plant to save up energy fortimes when it may need it, suchas when producing seeds.

• Many plants that use their tap

root as a source of foodactually create tap roots thathumans find appealing as well,and the so-called rootvegetables are generally plants



AERIAL ROOT

• You can see aerial roots on English Ivy,Poison Ivy, Trumpet Creeper, and lotsof other vines and creepers.

•

Aerial roots anchor climbing stems tovertical surfaces. the vine's aerialroots stick to one of the slats of ayellow-painted window shutter. Thediagonal item is the vine's stem,

which in real life is about the size of asmall lollipop's rolled-paper handle (2mm diameter), and you can plainlysee how each tendril of the aerial rootends in a flat appendage that sticks tothe slat's old paint..



Example of aerialroot



• These things stick so well that whenlater we pulled the stem away, theroots broke but the stickers stayedstuck. Remember that here we areseeing roots arising from along the

plant's stem, not at it's base.• You could follow this stem to the

ground and then below the ground

you'd find regular fibrous roots.



• Function

–

The main job of these aerial roots isto support the vine as it climbs upthe window shutters, not to absorbwater and nutrients.

– Organs arising where they are nottypically found, such as these rootsarising from along a stem, are saidto be adventitious



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Types of Root