Roots, Stems & Leaves Ch 23.2

Roots Roots function as an _________ and are capable of absorbing _________ and dissolved minerals. They also have _________________ for transporting water & nutrients. Ideally roots want a large _____________ for absorbing water and dissolved minerals. anchor water vascular tissue surface area

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

Roots

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

taproot fibrous root

Root structure Let’s look at the layers within a root, starting out and working our way in. cortex endodermis epidermis pericycle Xylem & phloem INSIDE OUTSIDE

Root structure 5 4 epidermis The outermost structure on a root are ______________ which increase surface area, ultimately allowing more water, oxygen, & dissolved minerals to be absorbed epidermis 5 Next layer = cortex The cortex transports water and dissolved minerals into vascular tissue Mostly parenchyma cells that store food, water 4

Root structure 3 2 Next layer = pericycle Produces lateral roots Next layer = endodermis A layer of waterproof cell walls around vascular tissue This layer controls water flow & dissolved minerals into roots 3 Next layer = pericycle Produces lateral roots 2

Root structure 1 Xylem & phloem = in center of root monocot = vascular bundles surround central core aka pith dicot = central star 1

Root structure root hairs cortex endodermis epidermis pericycle Xylem & phloem INSIDE OUTSIDE

Makes it longer Protection

epidermis

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

Stem Supports leaves and flowers Has vascular tissue to transport water, dissolved minerals, sugars Herbaceous or woody 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 (dicot) monocot dicot

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

Woody Stems Tissue layers outermost innermost vascular cambium phloem bark xylem outermost innermost Tissue layers

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

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

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

leaf blade

Leaf structure Outermost layer = Epidermis Next = Mesophyll: Photosynthesizing tissue of leaf Palisade mesophyll = photosynthesis occurs here Spongy mesophyll = has lots of air pockets for CO2, O2, & water vapor to exit via stomata

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

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