UT Arlington BIOL BIOL 3427 - ch7 (11 pages)

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ch7



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ch7

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Pages:
11
School:
University of Texas at Arlington
Course:
Biol Biol 3427 - Plant Science
Plant Science Documents

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Chapter 7 ROOTS FUNCTIONS OF THE ROOT 1 2 3 4 Anchorage Absorption and conduction of water and minerals Storage of food Production of some hormones and secondary metabolites The cylindrical shape of the root allows all sides to have the same absorptive capacity The cylindrical shape also facilitates the penetration of the root through the soil EXTERNAL STRUCTURE OF THE ROOTS Taproot system Produced by gymnosperms eudicots and magnoliids The primary root originates in the embryo derived from the embryonic radicle It grows downward and is called then a taproot It produces lateral roots branch roots This system generally penetrates deep into the soil Fibrous root system It is found in monocots The primary root originates from the embryonic radicle It is short lived Adventitious roots develop from the stem This system is usually shallow Many eudicots are perennial and undergo secondary growth resulting in an increased quantity of functional tissue The taproot system allows an increase in the absorptive capacity of the roots to satisfy the demands of the above ground tissues Monocots do not have secondary growth and after their tracheary elements mature their conducting capacity cannot increase Extra leaves could not be supplied with water and minerals and the demands of the secondary growth of a taproot system could not be satisfied The fibrous root system is the most practical for monocots Some monocots add new tissue through the growth of stolons The stolons produce adventitious roots at regular intervals to supply the new growth with an adequate supply of water and nutrients Feeder roots are those laterals that are actively engaged in absorption of water and minerals Most of the absorption of water and minerals takes place in the upper 15 cm of soil the area richest in organic material Desert plants can have very long taproots that penetrate deep into the soil A mesquite bush near Tucson AZ had roots 53 3 m or 175 feet deep into the soil Acacia and Tamarix trees



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