Roots

Front 1

Root

Back 1

an organ that typically originates from the lower portion of a plant or cutting, grows downward, has a rootcap and lacks nodes, so it never flowers or has leaves

Front 2

Functions

Back 2

-Absorption of H2O and nutrients dissolved in it
-Anchorage and Support
-Supply Oxygen
-Vegetative propagation
H2O storage in xerophytic plants in special cells with high colloid content for H2O to adhere to
-synthesis of organic molecules, including some hormones
-Give off CO2, which when combined with H2O forms carbonic acid to help dissolve a path for the root through the soil
-Haustoria of parasitic plants penetrate and absorb nutrients

Front 3

Extension of roots

Back 3

generally extend past the dripline, unless there is one very long taproot
Shallow rooted crops (radish or strawberry) of 1' will use all available water from a sandy loam soil in about 1 week (well established beans, lettuce, etc 2' available H2O 2 weeks, etc)

Front 4

Young vs old needs for H2O

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Young crops, transplants, seedlings and cuttings need more H2O than the same plant later; however as the plant ages, it will require more frequent H2O

Front 5

Primary and Secondary Growth

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Primary growth arises from cells produced by the apical meristem and result in increased length; secondary growth occurs in the vascular cambium in Dicots and Gynosperms

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Root cap

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Thimble-like structure of loosely arranged parenchyma cells that cover the root tip; secretion of CO2

Front 7

Apical Meristem

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region of elongation or enlargement; consists of cells that are enlarging and just beginning to differentiate. (3) meristems are evident

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Protoderm

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Single layer of cells on the outside, that will differentiate into the epidermis

Front 9

Ground Meristems

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Several cell layers thick, extending from the protoderm to near the center. These cells within this region will differentiate into the cortex and the endodermis

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Procambium

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Several layers of cells that occupy the central region. It will give rise to the tissues of the stele.

Front 11

Region of Maturation

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Root hair zone; where cells reach their final form (and can be seen); Each root hair is an extension of the cell wall

Front 12

Epidermis

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single layer of cells, not highly cutinized as in stems

Front 13

Cortex

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broad region of parenchyma where most starch is stored

Front 14

Endodermis

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single layer of cells with Casparian strips of suberin on the transverse and radial walls. May also be lignified.

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Pericylcle

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one of several layers of parenchyma that remain easily able to become meristematic in order to initiate branch roots

Front 16

Primary Phloem

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most sieve tube elements and companion cells; fewer fibers than stems, so more flexible

Front 17

Primary Xylem

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complex tissue as in stems. Protoxylem matures first, then metaxylem. The vascular cylinder or stele is enclosed in endodermis

Front 18

Monocot vs Dicot stem center

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Monocots center is pith made of parenchyma and dicots have a vascular cambium between the xylem and phloem. Monocot pericycle is several cells thick, while in dicots the pericycle is one cell thick

Front 19

Secondary root growth

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seen in dicots and gymnosperms; each year the vascular cambium produces new xylem and phloem just as in stems. The center remains an exarch configuration of xylem and phloem with at least 3 arms. After a year, the vascular cambium forms a ring as in stems, making xylem to the inside and phloem to the outside. Eventually a cork cambium differentiates and begins to produce cork and cork parenchyma, therefore older roots have bark.

Front 20

Carrot roots

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are almost all stele, they lack a cortex

Front 21

Adventitious Roots

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Prop roots in corn Aerial roots of aeroid also used for support Climbing roots of vines like English Ivy roots on cuttings

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Storage roots

Tuberous roots

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are starchy as in carrot.

are fleshy as in a sweet potato

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Roots in symbiotic relationships

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Nodule forming bacteria fix atmospheric N and get CHO in return (ie Rhizobia on legumes HOST SPECIFIC

Front 24

Mycorrhizae or fungus roots

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have been reported in most groups of vascular plants. Many forest trees can't live without them as they help to absorb essential nutrients such as P, K, Ca, N, Zn, Cu, an Mo. In return, they get CHO and vitamins

Front 25

Endomycorrihizae

Ectomycorrhizae

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fungal filaments extend from the soil into the cortex cells

less common, either form a mantle around the roots or invade the space between the cortical parenchyma cells or both