Plant Anatomy and What Part Are You Eating

Horticulture and the Science of Plants
Horticulture Youth Adventure Program

David Wm. Reed, Instructor
Department of Horticultural Sciences
Texas A&M University

BACKGROUND

Did you ever wonder why the wood of trees has rings?

Did you ever walk down the isle of a grocery store and notice all the odd looking fruits and vegetables and wonder where they come from?

Did you ever wonder where the leaves on a cactus are?

Did you ever brush up against a plant, and it started smelling like perfume?

We can answer all these questions and many more by knowing the parts plants and their structure. This is called anatomy. Today we are going to take a tour of plant anatomy.

Plants can be divided into 4 organs: 1) stems, 2) roots, 3) leaves, 4) flower and fruit. We are going to identify all the plant organs on “normal plants”, but we are going to also see really odd plant organs that you eat. For example, Irish potato tubers are modified stems; carrots and sweet potatoes are modified roots; celery stalks are modified petioles; tendrils, spines, poinsettia bracts and cabbage heads are modified leaves; and cauliflower and broccoli are modified flowers.

Also, we are going to talk about the difference between a fruit and a vegetable. Botanically, vegetables are structures that develop from one of the 3 vegetative organs (stems, roots or leaves); for example potato, carrot and onion. Whereas, fruits develop from the flower, for example, tomato, bell pepper, strawberry, corn, pineapple and apple. But in everyday life many fruits are commonly called vegetables, such as tomato. We will find out why. So let’s take a tour of the anatomy of plants – and if it’s good to eat, we’ll eat our way along the tour.

TAKE HOME LESSONS

1) To learn to identify the four plant organs and their modifications.

2) To observe how the organs are modified in the fruits and vegetable we eat.

3) To learn how to recognize the difference between botanical vegetables, fruits and seeds, and horticultural vegetables, fruits and seeds.

MATERIALS NEEDED

fresh samples of plant parts

PROCEDURES

1) The class will examine the parts of plants and a wide variety of fruits and vegetables.

2) The class will examine all the different kinds of fruit, and eat quite a few in so doing!

TYPES OF ROOTS
Fibrous Root Fibrous roots are the most common and they are the roots that absorb most of the water and nutrients plants require. grass plant	Taproot Some plants have taproots. The taproot is very deep in the soil for anchorage and to absorb deep sources or water. Sometimes the root is longer that the top of the plant. weed
Adventitious Root Adventitious roots are roots that come out of stems and leaves. When you cut a stem or leaf cutting off a plant, adventitious roots form to supply a new root system for the plant. peperomia leaf cutting	Tuberous Root Tuberous roots are storage roots that store food and water for the plant. Many of the vegetables we eat are tuberous roots such as beet, carrot, radish, and turnip. beet

TYPES OF LEAVES
Simple Leaves Simple leaves have one leaf blade. The leaf may be irregularly shaped, but it is still one blade with one leaf stalk.
Non-lobed Simple Leaf ficus leaf.	Lobed Simple leaf ornamental sweet potato
Compound Leaf Compound leaves are made of many individual leaflets that are all attached to the same leaf stalk
Feather-Like Compound Leaf (pinnate) rose	Palm-Like Compound Leaf (palmate) Texas mountain laurel

LEAVES THAT ARE MODIFIED
Modified Leaves Some leaves have many unusual shapes and sizes. This allows them to adapt to protect the plant, to store food, or to adapt to the environment in which they grow.
Scale Leaf cedar or juniper	Needle pine
Succulent storage leaf sedum	Food storage leaf onion bulb
Spine prickly pear cactus	Tendril grape ivy

STEMS

Parts of a Stem

Growth Rings of Wood

Woody plants in our part of the world (the temperate region) usually produce 1 growth ring every spring/summer. The age of the tree can be determined by counting the number of rings. (image from http://www.dsisd.k12.mi.us/mff/Environment/TreePhys.htm)

STEMS THAT ARE MODIFIED Many plants have stems that are modified to protect the plant, conserve water, spread by growing horizontally above or below the ground, or store water or food.
Thorns rose	Leaf-Like Stems (cladophyll) prickly pear
Underground Stems (rhizome) sansavieria	Horizontal Stems (runners and stolons) grass
Flat Plate-Like Stems (bulb) onion	Storage Stems (tuber) Irish potato

FLOWERS AND FRUITS
Parts of a Flower hibiscus
Parts of a Fruit The fruit develops from the ovary of the flower. Fruit contain one or more seeds inside. The function of the fruit is to protect the seeds or help spread the seeds. Some fruit are fleshy when they are ripe. They want to be eaten by animals and birds so their seeds will be spread. Some fruit are dry when they are ripe; this makes them tough.
fleshy fruit peach	dry fruit pecans and oak acorn

DRY FRUIT Some fruit are dry when they are ripe. Very often dry fruit are considered seeds.
Pods (legume) peanut	Capsule okra
DRY FRUIT THAT ARE CONSIDERED SEEDS
Flying Fruit (samara) green ash	Nuts pecan and oak acorn
Grain corn	Achene sunflower

FLESHY FRUIT Many fruit are fleshy when they are mature. Some are called vegetables. Which ones do you consider vegetables and which do you consider fruit? Do you know why?
Berry tomato	Cucurbits (pepo) yellow squash
Citrus (hesperidium) lemon	Stone Fruits (drupe) peach
Pome Fruits (pome) apple	Fruit Clusters (multiple fruit) pineapple