 Plants have 3 main organs: roots, stems, & leaves

 Roots – absorbs water and dissolved nutrients, anchors the plant, protect the plant from bad soil, and transports water to rest of the plant  Stems – support system for the plant body, transport system for water and nutrients  Leaves – plants main photosynthetic system

 Plants rely on specialized tissue, called vascular tissue, to transport water, nutrients, and the products of photosynthesis around the plant.  The 2 types of vascular tissue are xylem and phloem.

What is xylem? Transports water from the roots up to the rest of the plant in one way flow. What are tracheids? Hollow cell in xylem with thick cell walls that resist turgor pressure

 Water rises through the thin tubes by a process called capillary action (cohesion of h20 molecules and adhesion to solid surface). The thinner the tube, the higher the water will rise.  Plants lose water through their stomata in a process called transpiration. As the leaves lose water, more is drawn up the plant (like liquid through a straw).  The actions of these two forces, along with root pressure (Root pressure occurs in the xylem when the soil moisture level is high either at night or when transpiration is low during the day), allows water to be delivered to the entire plant, even to ones that are a hundred feet tall.

 Vascular tissue that transports sugars (glucose) produced by photosynthesis to plants in a two-way flow to the roots of the plant. - dripping sap(sugars) coming from a tree is usually from the phloem

 When nutrients are pumped into or removed from the phloem system, the change in pressure causes a movement of nutrients in that same direction. As a result, phloem is able to move nutrients in either direction to meet the nutritional needs of the plant.

Functions:  absorb water and nutrients from the soil  anchor plants in the ground  hold soil in place and prevent erosion  protect plant from harmful soil bacteria and fungi  hold plants upright against forces such as wind and rain.

 Taproot  Typical in Dicots  Single large root  Able to penetrate to deep water source  Ex. Radishes and Dandelions  Fibrous Root  Typical in Monocots  Many branched roots of similar length  Prevents soil erosion

Adventitious Roots Cypress trees have root “knees” that extend above ground.

Prop Roots: Mangrove Islands

More Prop Roots Contractile Roots

Root Structures Roots have root hairs, which increase the surface area of roots, thus increasing the amount of water absorbed. Refer to the picture to view a root’s apical meristem. Meristem tissue is the only plant tissue that produces new cells by mitosis. Thus, roots only grow from the tips (apical) where the meristem tissue is located.

Xylem and Phloem in Plant Roots One of the reasons Angiosperms are divided into monocots and dicots is there roots. In Dicots, the xylem makes an X in the center of the root, and the phloem fills around it. In Monocots, the xylem makes a ring, rather than an X, and is surrounded by a ring of phloem. Dicot root (notice the X).

The vascular tissue in the dicot is spread throughout the root while the vascular tissue in the monocot is just around the outer ring of the root.

 Composed of a Node, Internode, and Bud  Three main functions of a stem: 1. Produce leaves, branches, and flowers 2. Hold leaves up to sunlight (support) 3. Transport substances between roots and leaves

Leaves attach to stems at areas called nodes. Internodes are the areas between the nodes, and buds contain undeveloped tissue that will produce new stems and leaves. Stem Buds Like roots, stems have apical meristems for growth. The apical meristems contain hormones that cause the stems to grow in height. If the apical meristems are removed, the plant grows side branches instead. Apical meristem of shoot Leaves

Stems

Bulbs – made of a central stem surrounded by short, thick leaves. The leaves wrap around and protect the stem and also store food. It may remain dormant for a long time. Tubers- stems that store food (usually grow underground) Beets Onion Potato

 Monocot  Vascular bundles are scattered  Dicot  Vascular bundles are in a ring

Functions:  most photosynthesis takes place here  absorb sunlight  contain pores for gas exchange

 Blade- thin, flattened surfaces of leaves that increase surface area for absorption of sunlight.  Petiole- thin stalk that attaches the leaf blade to the stem. General Structure

Dicot – makes an X in the middle Monocot – makes a ring around outer edge.

 Monocot Dicot  Vascular bundles * Vascular bundles are scattered are in a ring

Guard Cells Stomata (stoma)Cuticle Epidermis Vascular bundle (vein) Chloroplasts

Guard cells: cells that open and close the stoma Stomata: openings in underside of leaf’s surface; when open: GAS EXCHANGE: Allows CO 2 in & O 2 out of leaf TRANSPIRATION: Allows excess H 2 O out of leaf

GUARD CELL WITH STOMATA

A average size maple tree can transpire 200 liters of water per hour during the summer. Transpiration is the #1 driving force for pulling water up stems from roots. 1.Transpiration: loss of excess water from plant leaves 2. Significance: a.Transpiration causes enough pressure to help pull water (& required nutrients) up stem from roots. b.As part of the water cycle, trees transpire water back into the atmosphere. c.Transpiration provides much of the daily rain in rainforest.