1. Plant Tissue and Growth
What organs do plants have?

2. Section 1: Plant Cell Structures
The large central vacuole is surrounded by its own membrane and contains water and dissolved substances.
Its primary role is to maintain pressure against the inside of the cell wall, giving the cell shape and helping to support the plant.
The cell wall is located outside the cell membrane. It consists mainly of cellulose and may also contain lignin, which makes it more rigid.
The cell wall shapes, supports and protects the cell. It prevents the cell from absorbing too much water and bursting. It also keeps large, damaging molecules out of the cell.
Plastids are membrane-bound organelles with their own DNA. Ex: Chloroplasts and chromoplasts.
Chloroplasts contain the green pigment chlorophyll and carry out photosynthesis.
Chromoplasts make and store other pigments, they give flower petals bright colors.

3. Plant Tissues
Dermal Tissue – covers the outside of a plant in a single layer of cells called the epidermis. It is like the plant’s skin.
These cells secrete a waxy substance called cuticle, which coats, waterproofs, and protects the above-ground parts of plants. This prevents water loss, abrasions, infections, and damage from toxins.
Ground Tissue – makes up much of the interior of a plant and carries out basic metabolic functions.
In stems it provides support and may store food or water.
In roots it may also store food.
Vascular Tissue – runs through the ground tissue inside a plant.
Consists of xylem and phloem, which transport fluids.

4. Vascular Tissue
Xylem – a vascular tissue that transports water and dissolved minerals from roots to stems and leaves.
This type of tissue consists of dead cells that lack end walls between adjacent cells.
The side walls are thick and reinforced with lignin, which makes them stiff and water proof.

5. Vascular Tissue
Phloem – vascular tissue that transports food (sugar dissolved in water) from photosynthetic cells to other parts of the plant for growth or storage.
This type of tissue consists of living cells that are separated by end walls with tiny perforations, or holes.

6. Growth of Plants
Plants grow throughout their lives. Plants grow through a combination of cell growth and cell division.
Cell growth increases cell size, while cell division (mitosis) increases the number of cells.
As plant cells grow, they also become specialized into different cell types through cellular differentiation.
Once cells differentiate, they can no longer divide.
The key to continued growth and repair of plant cells is meristem.
Meristem is a type of plant tissue consisting of undifferentiated cells that can continue to divide and differentiate.
Meristem at the tips of roots and stems allows them to grow in length, this is called primary growth.
Meristem within and around vascular tissues allows growth in width, this is called secondary growth.

7. Section 2: Plant Organs
Plants have specialized organs that help them survive and reproduce in a great diversity of habitats.
Major organs of most plants include roots, stems, leaves, and flowers.
A plant has 2 organ systems:
The shoot system – is above the ground and includes the organs such as leaves, stems, flowers and fruits.
The root system – includes the parts of the plant below ground, such as roots.

8. Roots Roots are important organs in all vascular plants.
Two types of roots:
Primary roots grow downward
Secondary roots branch out to the side.

9. Root Systems Two Basic Types: Taproot systems and Fibrous systems
Taproot systems – feature a single, thick primary root, called the taproot, with smaller secondary roots growing out from the sides.
The taproot may penetrate as many as 200 feet below the ground surface.
It can plumb very deep water sources and store a lot of food to help the plant survive drought and other environmental extremes.
The taproot also anchors the plant very securely to the ground.

10. Root Systems Two Basic Types: Taproot systems and Fibrous systems
Fibrous root systems have many small branching roots, called fibrous roots, but no large primary root.
The huge number of threadlike roots increases the surface area for absorption of water and minerals, but fibrous roots anchor the plant less securely.

11. Root Structures and Functions
The tip of the root is called the root cap.
It consists of specialized cells that help regulate primary growth of the root at the tip.
The root cap is primary meristem, where growth in length occurs.
The rest of the root is covered with a single layer of epidermal cells.
These cells may have root hairs that increase the surface area for the absorption of water and minerals from the soil.
Beneath the epidermis is ground tissue, which may be filled with stored starch.
Bundles of vascular tissue form the center of the root. Secondary meristem is located within and around the vascular tissues.

12. Primary Functions of Roots
Absorbing water and minerals
Thin walled epidermal cells and root hairs are well suited to absorb water and dissolved minerals from the soil.
Anchoring and supporting the plant
Root systems help anchor plants to the ground, allowing plants to grow tall without toppling over.
A tough covering may replace the epidermis in older roots, making them ropelike and even stronger.
Storing food
In many plants, ground tissues in roots store food produced by the leaves during photosynthesis.

13. Root Growth
Roots have primary and secondary meristems for growth in length and width.
As roots grow longer, they always grow down into the ground. Even if you turn a plant upside down, its roots will try to grow downward.
Specialized cells in root caps are able to detect gravity. The cells direct meristem in the tips of roots to grow downward toward the center of Earth.

14. Stems
In vascular plants, stems are the organs that hold plants upright so they can get the sunlight and air they need.
Stems also bear leaves, flowers, cones, and secondary stems.
These structures grow at points called nodes.
At each node, there is a bud of meristem tissue that can divide and specialize to form a particular structure.

15. Stem Tissues and Functions
A single-celled layer of epidermis protects and waterproofs the stem and controls gas exchange.
In trees, some of the epidermal tissue is replaced by bark. Bark is a combination of tissues that provides a tough, woody external covering on the stems of trees. The inner part of bark is alive and growing; the outer part is dead and provides strength, support and protection.

16. Stem Tissues and Functions
Ground tissue forms the interior of the stem. The large central vacuoles of ground tissue cells fill with water to support the plant. The cells may also store food.
Bundles of vascular tissue run through the ground tissue of a stem and transport fluids. Plants may vary in how these bundles are arranged.

17. Stem Growth
The stems of all vascular plants get longer through primary growth. This occurs in primary meristem at the tips and nodes of the stems.
Most stems also grow in thickness through secondary growth. This occurs in secondary meristem, which is located in and around the vascular tissues.
Secondary growth forms secondary vascular tissues and bark. In many trees, the yearly growth of new vascular tissues results in an annual growth ring.

18. Leaves
Leaves are the keys not only to plant life but to all terrestrial life.
The primary role of leaves is to collect sunlight and make food by photosynthesis.

19. Factories for Photosynthesis
You can think of a single leaf as a photosynthesis factory. A factory has specialized machines to produce a product. It’s also connected to a transportation system that supplies it with raw materials and carries away the finished product. In all these ways, a leaf resembles a factory. The cross section of a leaf in the figure below lets you look inside a leaf “factory.”

20. Factories for Photosynthesis
Mesophyll makes up most of the leaf’s interior. This is where photosynthesis occurs. Mesophyll consists mainly of parenchymal cells with chloroplasts.
Veins are made primarily of xylem and phloem. They transport water and minerals to the cells of leaves and carry away dissolved sugar.
A leaf consists of several different kinds of specialized tissues that work together to make food by photosynthesis. The major tissues are mesophyll, veins, and epidermis.

21. Factories for Photosynthesis
The epidermis of the leaf consists of tightly-packed dermal cells. They secrete waxy cuticle to prevent evaporation of water from the leaf.
The epidermis has tiny pores called stomata (singular, stoma) that control transpiration and gas exchange with the air.

22. Flowering Plants
Angiosperms, or flowering seed plants, form seeds in ovaries.
As the seeds develop, the ovaries may develop into fruits.
Flowers attract pollinators, and fruits encourage animals to disperse the seeds.

23. Parts of a Flower
A flower consists of male and female reproductive structures.
The main parts of a flower include the stamen, pistil, petals, and sepals.

24. Parts of a Flower
The stamen is the male reproductive structure of a flower. It consists of a stalk-like filament that ends in an anther.
The anther contains pollen sacs, in which meiosis occurs and pollen grains form.
The filament raises the anther up high so its pollen will be more likely to blow in the wind or be picked up by an animal pollinator.

25. Parts of a Flower
The pistil is the female reproductive structure of a flower. It consists of a stigma, style, and ovary.
The stigma is raised and sticky to help it catch pollen.
The style supports the stigma and connects it to the ovary, which contains the egg.
Petals attract pollinators to the flower. Petals are often brightly colored so pollinators will notice them.
Sepals protect the developing flower while it is still a bud. Sepals are usually green, which camouflages the bud from possible consumers.

26. Major Tissues in Plants
Function
Dermal Tissue
Compares to the skin, or epidermis in animals. Protects plant and intermediates between the plant and its environment.
Ground Tissue
Basic metabolic functions. Makes up most of the interior of the plant. Makes up most organs.
Vascular Tissue
Transports water, minerals and food throughout the plant.

27. Organ Functions Root Anchorage.
Absorption of water and dissolved minerals.
Storage (surplus sugars transported from leaves)
Conduction
Stem
Conduction of water and sugars throughout plant.
Support leaves and fruits.
Leaf
Perform photosynthesis
Regulate water loss of the plant
Abcission (leaf fall)
Flower
Contain reproductive organs
Attract pollinators
Produce fruit