Roots, Stems, and Leaves

Roots, Stems, and Leaves Three of the principal organs of seed plants are roots, stems, and leaves. Together these plant organs function in: Transport Protection Coordination of plant activities

Plant Tissue Systems Each part of a plant consists of 3 types of tissue: Dermal tissue Vascular tissue Ground tissue

Dermal Tissue The “skin” of a plant contains a “waxy” layer called a cuticle Functions to prevent water loss

Vascular Tissue Plants “bloodstream” Transports water and nutrients throughout the plant. Made of Xylem and Phloem

Xylem XYLEM = 5 letters WATER = 5 letters Water moving tissue The xylem is part of the vascular system of a plant. Similar to veins and arteries in animals. It also provides stability to the plant through turgor pressure. Damage to the xylem would effect how well the plant could move water throughout its tissue and it may not be able to support the weight of the leaves and branches (with decreased pressure).

Phloem PH- loem : F- ood Food transport tissue. Transports solutions of nutrients and carbohydrates Damage to the phloem can decrease or stop the flow of nutrients throughout the plant and cause all or part of the plant to die.

Nutrient Transport through Phloem Using the Phloem, many plants pump sugars out of the leaves and roots and into their fruit.

Ground Tissue Cells that lie between dermal and vascular tissue Made of cells whose cell walls have different thicknesses

Meristematic Tissue Just like our cells do! The only plant tissue that produces new cells by mitosis Located at the tips of stems and roots Apical Meristem - increase plant length Cells start out alike but then differentiate Just like our cells do!

Roots Two main types: Taproots – The taproot and its lateral roots penetrate deeper into the soil than fibrous roots. Found mainly in dicots. Fibrous roots usually do not penetrate the soil very deeply. Because their roots attach themselves firmly to soil particles, plants with fibrous root systems are especially useful in preventing soil erosion. Found mainly in monocots.

Root Structure and Growth The root’s surface is covered with cellular projections called root hairs. Root hairs provide a large surface area through which water and nutrients can enter the plant. Root hairs A root consists of a central vascular cylinder surrounded by ground tissue and the epidermis. Root hairs along the surface of the root aid in water absorption. 12

Root Function 1. Anchor a plant 2. Absorb water 3. Absorb dissolved nutrients

Root Functions Minerals enter the roots through active transport. Water enters by osmosis Root hairs Roots absorb water and dissolved nutrients from the soil. Most water and minerals enter a plant through the tiny root hairs. Active transport of minerals Movement of water by osmosis 14

Examples of Root Vegetables Carrot Sweet Potato Parsnip Radish Ginger A root consists of a central vascular cylinder surrounded by ground tissue and the epidermis. Root hairs along the surface of the root aid in water absorption. 15

Stems- Functions Produce leaves, branches and flowers Hold leaves up in the sunlight Transport various substances between roots and leaves

Examples of Stem Vegetables Asparagus Rhubarb Bamboo Celery

Leaves The structure of a leaf is optimized for absorbing light and carrying out photosynthesis. The leaves and stems together form shoots.

Example of Leaf Vegetables Lettuce Spinach Cabbage Basil Brussel Sprouts Broccoli

Why don’t Plants dry out in the sun? Stomata are pore-like openings in the underside of the leaf that allow carbon dioxide and oxygen to diffuse into and out of the leaf. Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excessive amount of water through transpiration. Transpiration is the evaporation of water through plant leaves. The stomata open and close in response to changes in water pressure within the guard cells. When it is dry, the stomata are closed. When there is enough water the stomata are open

Monocots vs Dicots

Transport in Plants Root pressure – the starting point for the movement of water through the vascular system of the plant. Capillary Action – The tendency of water to rise in a thin tube. Transpiration – loss of water through a plant’s leaves. All work together to move water through xylem tissue of even the tallest plant.

Transport in Plants The ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. Paper towels absorb liquid through capillary action, allowing a fluid to be transferred from a surface to the towel. The small pores of a sponge act as small capillaries, causing it to absorb a comparatively large amount of fluid. Some modern sport and exercise fabrics use capillary action to "wick" sweat away from the skin. Video? Water Transport (3:14)

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