Instructional Materials Service Plant Science Plant Structures Instructional Materials Service Texas A&M University - 8384 -

Plant Structures Parts of a Vascular Plant Root Structure Stem Structure (External) Leaf Structure Parts of a Complete Flower

Plant Cell Anatomy

Parts of a Vascular Plant

Plant Organs Plant organs include their roots, stems, leaves, and reproductive structures. Each plant organ performs a specialized task in the life of a plant. Roots, stems, and leaves are all vegetative structures. Flowers, seeds, and fruits make up reproductive structures.

Plant Organ Functions Roots support the plant and supply it with water and nutrients. Stems connect the root and leaves. Leaves capture energy from the sunlight and use it to make food for the plant. Reproductive structures attract pollinators and produce seeds and fruits.

To help prevent soil erosion, which root system would be best? Fibrous

Taproots Disadvantages Difficult to remove or harvest Penetrates deeper Obtain water from other levels Anchor plant Disadvantages Difficult to remove or harvest do not stabilize well

PARTS OF PLANT ROOT

Fibrous Advantages Shallower, better for fertilization & Water Disadvantage Less drought resistant Tend to get exposed during cultivation Advantages Shallower, better for fertilization & Water Stabilize in soil better

Primary Roots Grow down into the soil and may branch repeatedly into lateral roots Taproot is a primary root

Lateral Roots Called Secondary roots grow horizontally away from the primary root Some grow downward

Root Structure Epidermis Cortex Zone of Differentiation Root Hairs Phloem Tubes Xylem (water transport) Zone of Elongation Root Cap Meristem

The Epidermis The epidermis is the outermost layer of cells surrounding the root. The cells of the epidermis are responsible for absorbing water and minerals from the soil Epidermis

The Cortex The cortex is a layer of tissue between the epidermis and the vascular tissue. Cortex cells function in the movement of water and in food storage. Cortex

Root Hairs Root hairs are found along the main root and perform much of the actual work of water and nutrient absorption. Most plants produce root hairs that only live a few days or a few weeks. As a plant grows, new root hairs form. Root Hairs

Xylem Xylem is the supporting and water conducting tissue of vascular plants. Xylem

Phloem Phloem is the food conducting tissue of vascular plants, made up of sieve tubes and other cellular material. Phloem

Meristem The meristem is at the tip of the root and is responsible for manufacturing new cells. This is the area where cell division and growth occur. Meristem

Roots The root is the first plant structure to emerge from a seed during germination. Roots are mostly found below the soil surface and represent about 50% of a plant’s weight. The primary functions of roots are to absorb water and nutrients from the soil and to support the plant in an upright position.

Root Functions Roots distribute the food energy produced in the leaves to the rapidly growing areas found at the root tips. Some plants use their roots as a specialized food storage reserve. The first root to emerge from a seed is the primary root, or radicle.

Roots (taproot) Plant root systems are classified based on the relative sizes of their primary and secondary roots. Plants such as dandelions, carrots, turnips, and most trees have a taproot. In taproot systems, the primary root thickens and becomes the dominant root.

Roots (fibrous) In fibrous root systems, the primary and secondary roots are of similar diameter. They remain fairly close to the soil surface. Fibrous root systems help to prevent the erosion of topsoil during heavy rains. Plants such as onions, grasses, and corn have fibrous root systems.

Root Types Tap Root Fibrous Roots

Stem Characteristics

Stems Stems function as supportive structures. They hold a plant’s leaves up toward the sun so the leaves can capture energy from sunlight. Stems transport water and nutrients from the roots to the leaves, and food energy from the leaves to the roots.

Leaf Structure Vein Midrib Expanded Portion of Blade (Lamina) Axillary Bud Bladestalk (Petiole) Node Internode Base of Leaf

Leaf Characteristics

Midrib & Veins The midrib is the most prominent, central vein in a leaf. Lateral veins are secondary veins that branch from the midrib. Both midribs and lateral veins contain vascular tissue. Vein Midrib

Leaf Blade (Lamina) Leaf Blade (Lamina) The expanded flat portion of a leaf is the leaf blade, or lamina.

Petiole (Bladestalk) The petiole attaches the lamina to the plant stem. Petiole

Axillary Bud An axillary bud exists on the stem just above the point where the leaf petiole attaches to the stem. Axillary Bud

Parts of a Flower Pollen Grains Stigma Filament Style Anther Petal Pollen Tube Ovule Embryo Sac Sepal Microphyle Integuments Ovary Receptacle

Complete Flowers Compete flowers have four basic parts: Sepals Petals Stamens Pistil

Sepals Sepals are leaf-like structures that form an outer ring around the base of a flower. Sepals enclose and protect a flower bud before it opens. The complete ring of sepals is called the calyx. Sepals

Petals Petals are often the bright and colored part of a flower. Petal colors and scents attract specific pollinators. Petals

Stamens The stamen contains both the filament and the anther. The filament is a stalk-like structure that holds the anther. Stamens are the male reproductive parts of a flower. Filament

Pistil The pistil includes three parts: 1. Stigma 2. Style 3. Ovary

Pistil 1. Stigma The stigma is a sticky, flattened surface that projects upwards towards the pollinator. Birds and insects collect nectar from previously visited plants and brush against the sticky surface of the stigma. Stigma

Pistil 2. Style The style is a supportive structure that holds the stigma in a position to maximize the chances of pollination. Style

Pistil 3. Ovary The ovary is an enlarged structure that contains the female sex cells, or ovules. The pollen tube grows through the ovary and into an ovule. Pollen Tube Ovary Ovule

Receptacle The enlarged part of the pedicel where it joins the flower is the receptacle. Receptacle

Pedicel The pedicel (flower stalk) supports the flower. Pedicel

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Acknowledgements Kristi Falco, Graduate Assistant, Instructional Materials Service, researched and developed the information used in this PowerPoint Presentation. Christine Stetter, Artist, Instructional Materials Service, developed and illustrated this PowerPoint Presentation.. Keith Zamzow, Curriculum Specialist, Instructional Materials Service, edited and reviewed this PowerPoint Presentation. Vickie Marriott, Office Software Associate, Instructional Materials Service, edited this PowerPoint Presentation.

ALL RIGHTS RESERVED Reproduction or redistribution of all, or part, of this presentation without written permission is prohibited. Instructional Materials Service Texas A&M University 2588 TAMUS College Station, Texas 77843-2588 http://www-ims.tamu.edu  2006