Roots Stems Leaves Ch 23 2 Roots o

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Roots, Stems & Leaves Ch 23. 2

Roots, Stems & Leaves Ch 23. 2

Roots o Roots function as an _____ and are capable of absorbing _____ and

Roots o Roots function as an _____ and are capable of absorbing _____ and dissolved minerals. o They also have _________ for transporting water & nutrients. o Ideally roots want a large _______ for absorbing water and dissolved minerals.

Roots o They vary in shape: short, long, thick, thin, massive, threadlike o Ideally

Roots o They vary in shape: short, long, thick, thin, massive, threadlike o Ideally roots want a large _______ for absorbing water and dissolved minerals.

Roots

Roots

Roots o There are 2 types of root systems (depends on environment). n A)

Roots o There are 2 types of root systems (depends on environment). n A) taproot = single, thick structures (ex: carrots, beets) n B) fibrous roots = many, small branching roots (ex: grasses, clovers)

taproot fibrous root

taproot fibrous root

Root structure o Let’s look at the layers within a root, starting out and

Root structure o Let’s look at the layers within a root, starting out and working our way in. is rm e d cle do y ic en er p x c te or is m er id p e Xylem & phloem INSIDE OUTSIDE

Root structure The outermost structure on a root are _______ which increase surface area,

Root structure The outermost structure on a root are _______ which increase surface area, ultimately allowing more water, oxygen, & dissolved minerals to be absorbed Next layer = cortex o. The cortex transports water and dissolved minerals into vascular tissue o. Mostly parenchyma cells that store food, water

Root structure Next layer = endodermis o A layer of waterproof cell walls around

Root structure Next layer = endodermis o A layer of waterproof cell walls around vascular tissue o This layer controls water flow & dissolved minerals into roots Next layer = pericycle o Produces lateral roots

Root structure Xylem & phloem = in center of root o monocot = vascular

Root structure Xylem & phloem = in center of root o monocot = vascular bundles surround central core aka pith o dicot = central star

Root structure s t o ro is ic le c y r pe do

Root structure s t o ro is ic le c y r pe do n e rm e d x te or ir a h is rm c e d i p e Xylem & phloem INSIDE OUTSIDE

Makes it longer Protection

Makes it longer Protection

epidermis

epidermis

Root growth o Region where roots grow in length = ________ o As these

Root growth o Region where roots grow in length = ________ o As these newly created cells mature, they differentiate and take on specific functions. o The tip of root is covered by _____ (protective layer of parenchyma cells). o Also, vascular cambium in dicots increases the _____ of roots.

Stem o Supports leaves and flowers o Has vascular tissue to transport water, dissolved

Stem o Supports leaves and flowers o Has vascular tissue to transport water, dissolved minerals, sugars o Herbaceous or woody o Some stems store food (to survive harsh weather) ex: corn, tubers, & rhizomes

Internal structure of stems Vascular tissue appears in 2 arrangements: scattered (monocot) & circular

Internal structure of stems Vascular tissue appears in 2 arrangements: scattered (monocot) & circular (dicot)

Woody Stems o Examples: conifers, perennial dicots (have thick sturdy stems) o As plants

Woody Stems o Examples: conifers, perennial dicots (have thick sturdy stems) o As plants grow up they also g r o w o u t o The added thickness on sides aka “secondary growth. ” It is created by the vascular cambium. o Woody stems have visible annual growth rings with sclerenchyma fibers

Woody Stems outermost Tissue layers innermost

Woody Stems outermost Tissue layers innermost

Stems transport materials o Xylem transports _____ and dissolved minerals from _____ to _____

Stems transport materials o Xylem transports _____ and dissolved minerals from _____ to _____ o Phloem carries dissolved _____, hormones, viruses from _____ to ______ “sink” = any portion of plant that stores sugars (ex: parenchyma cells) “translocation” = movement of sugars in phloem

Growth in Stem The term “primary growth” refers to a plant increasing in length

Growth in Stem The term “primary growth” refers to a plant increasing in length along the stem at nodes where they give rise to branches and leaves.

Leaves o Primary function = __________ o Leaves want to have a large ________

Leaves o Primary function = __________ o Leaves want to have a large ________ to capture light. o Leaf blade = flat broad green structure (vary in size and shape) o Some leaves join directly to stem o Some leaves have a stalk that joins leaf blade to stem n The stalk of a leaf = petiole (has vascular tissue)

Leaf structure o Outermost layer = Epidermis o Next = Mesophyll: Photosynthesizing tissue of

Leaf structure o Outermost layer = Epidermis o Next = Mesophyll: Photosynthesizing tissue of leaf n n Palisade mesophyll = photosynthesis occurs here Spongy mesophyll = has lots of air pockets for CO 2, & water vapor to exit via stomata

Transpiration loss of water via stomata = aka transpiration Think PERSPIRATION… when you sweat

Transpiration loss of water via stomata = aka transpiration Think PERSPIRATION… when you sweat you lose water through your pores

Leaf modifications o A) Some plants release irritants when crushed or broken o B)

Leaf modifications o A) Some plants release irritants when crushed or broken o B) Another modification = cactus spines which are modified leaves (to reduce water loss). o C) Carnivorous plants use their leaves to trap insects. o D) Some leaves function as water or food storage sites (ex: aloe vera) o E) Bulb = shortened stem, flower bud and immature leaves n ex: onion, tulips, narcissus, lilies

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