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Dermal Tissue
Dermal Tissue
The outer covering of a plant consists of epidermal cells.
Epidermal cells make up dermal tissue.
The outer surfaces of epidermal cells are covered with a thick waxy layer, known as the cuticle. The cuticle protects the plant against water loss and injury.
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Leaf Structure
The epidermis of many leaves is covered by the cuticle.
Cuticle
Epidermis
Leaves absorb light and carry out most of the photosynthesis in a plant. Some of the most important manufacturing sites on Earth are found in the leaves of plants. The cells in plant leaves are able to use light energy to make carbohydrates.
Epidermis
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Vascular Tissue
Vascular Tissue
Vascular tissue forms a transport system that moves water and nutrients throughout the plant.
Vascular tissue is made up of xylem, a water-conducting tissue made of cells that have matured and died, and phloem, a food-conducting tissue. Xylem and phloem are found in the vascular cylinder.
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Leaf Structure
Vascular Tissues
All these tissues form the veins of a leaf.
Xylem
Vein
Phloem
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Vascular Tissue
Xylem
Vessel elements form a continuous tube through which water can move.
Tracheid
Vessel element
Vascular tissue is made up of xylem and phloem. Xylem tissue conducts water from the roots to the rest of the plant.
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Vascular Tissue
Phloem
Sugars and other foods can move through these holes from one adjacent cell to another.
Companion cell
Sieve tube element
Vascular tissue is made up of xylem and phloem. Phloem tissue conducts a variety of materials, mostly carbohydrates, throughout a plant.
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Water Pressure
The tendency of water to rise in a thin tube is called capillary action.
Water is attracted to the walls of the tube, and water molecules are attracted to one another.
Capillary action—the result of water molecules’ ability to stick to one another and to the walls of a tube—contributes to the movement of water up the cells of xylem tissue. As shown here, capillary action causes water to move much higher in a narrow tube than in a wide tube. Applying Concepts Which force—adhesion or cohesion—causes the water to stick to the walls of the glass tube?
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Water Pressure
Capillary action causes water to move much higher in a narrow tube than in a wide tube.
Capillary action—the result of water molecules’ ability to stick to one another and to the walls of a tube—contributes to the movement of water up the cells of xylem tissue. As shown here, capillary action causes water to move much higher in a narrow tube than in a wide tube. Applying Concepts Which force—adhesion or cohesion—causes the water to stick to the walls of the glass tube?
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Water Pressure
The movement of water out of the leaf “pulls” water upward through the vascular system all the way from the roots.
This process is known as transpirational pull.
Root pressure, capillary action, and transpiration contribute to the movement of water within a plant. Transpiration is the movement of water molecules out of leaves. The faster water evaporates from a plant, shown in A, the stronger the pull of water upward from the roots, shown in B.
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Ground Tissue
Ground Tissue
Cells that lie between dermal and vascular tissues make up the ground tissues.
The three kinds of ground tissue are:
parenchyma
collenchyma
sclerenchyma
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Ground Tissue
Parenchyma cells have thin walls and large central vacuoles surrounded by a thin layer of cytoplasm. Store starch, oils, and water. Similar to human skin, dead parenchyma cells that make up bark form dermal tissues.
Collenchyma cells have strong, flexible cell walls that help support larger plants.
Sclerenchyma cells have extremely thick, rigid cell walls that make ground tissue tough and strong. Found in the hard or gritty parts of fruits and vegetables.
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Leaf Structure
In leaves, xylem and phloem tissues are gathered together into bundles that run from the stem into the petiole.
In the leaf blade, the vascular bundles are surrounded by parenchyma and sclerenchyma cells.
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