Download Plant Recognition: Classification and Identification of Field Crop

Plant Recognition: Classification and Identification of Field Crop Plants
OVERVIEW
INSTRUCTOR:
UNIT: Performance of Technical Skills Related to Plant and Soil Science and Technology
LESSON: Plant Recognition: Classification and Identification of Field Crop Plants
IMS REFERENCE: IMS #8390
TOPIC NOTES
Taxonomists,* agronomists, agricultural producers, and scientists have grouped or
classified plants in various ways for many generations. Field crop plants include those
grown for food, feed, fiber, or industrial purposes. Agricultural producers often classify
field crops by methods used to plant the crops (see Table 1).
Many classification systems exist to group plants for identification purposes. Discussed in this
topic are various methods for classifying field crops. These methods include the classification of
field crops based on use, season of growth, and life span. Also discussed are the binomial
classification of plants and the characteristics of plants known as monocots and dicots used in
field crop classification and identification.
CLASSIFICATION OF FIELD CROPS ACCORDING TO USE
Field crops provide a source of many products we use in our daily lives. Figure 1 shows a sample
of various field crops and their classification according to use.
Cereal crops include those grown to furnish edible food and feeds. Cereal crops are members of
the grass family. Seven important cereal grasses are corn, wheat, rice, grain sorghum, barley,
oats, and rye. Triticale (a hybrid cross between wheat and rye) is a relatively new cereal grain.
Legume seed crops are members of the legume plant family. These crops are high in protein and
oil con- tent. Important legumes grown for their edible seeds include soybeans, peanuts, field
beans, garden peas, lentils, and cowpeas.
Forage crops include grasses and legumes grown as feed for animals. Forage crops for
feeding purposes are used in the form of silage, hay, and fodder. Grass forages include corn,
sorghum, oats, barley, and various low-growing pasture grasses. Legume forages include
alfalfa and clover.
* Underlined words are defined in the Glossary of Terms.
Instructional Materials Service
1
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Root crops have a high starch content. Important crops grown for their edible roots or root parts
include sweet potatoes, carrots, rutabagas, beets, and turnips.
Fiber crops are important for their fibrous parts. The textile industry uses raw materials from fiber
crops for the production of clothing, rope, twine, and other fiber related products. Cotton, flax,
and hemp are important fiber crops.
Sugar crops are a raw source for sugar products. Important sugar crops include sugar beets,
sugarcane, and sweet sorghum. Corn is also becoming more important as a source for sugar.
Oilseed crops are important for their high oil content. Cotton (cottonseed), soybean, flax, peanuts,
sunflowers, and castor beans are important oil seed crops.
Tuber crops are similar to root crops in that they also have a high starch content. Important tuber
crops include Irish (white) potatoes and artichokes.
Stimulant crops include tobacco, coffee, and tea.
Food crops include fruit and vegetable crops. These crops supply humankind with a force of
valuable vitamins and nutrients. These crops are not considered field crops. However, they are
very important in nutrition and agriculture. These crops include fruits such as apples, peaches,
plums, pears, and citrus crops. Important vegetable crops include potatoes, tomatoes, sweet corn,
lettuce, onions, cabbage, and other garden crops.
Timber crops are important industrial crops. Timber is an important material used for
construction purposes. Timber crops include pine trees and many varieties of hardwoods
produced specifically for timber harvesting.
Many crops provide raw materials for industrial purposes. Two important plants for industry are
the crambe and guayule for natural plastics and rubber, respectively.
CLASSIFICATION OF FIELD CROPS ACCORDING TO SPECIAL USES
Green-manure crops include clover, vetch, cowpeas, and soybeans. When plowed under the soil
during their latter growing stages, these crops supply nutrients and organic matter to improve soil
quality.
Cover crops include those planted to protect the soil against wind and water erosion and loss of
soil nutrients. Examples of cover crops include crimson clover, rye, vetch, oats, wheat, and
seasonal grasses.
Emergency (catch) crops are those quick-growing crops planted to replace other crops that have
failed. Such crops include sudangrass, rye, and millet.
Green-chop crops include crops that are cut green and fed, uncured, to livestock. Green-chop
crops include sorghum, alfalfa, corn, and soybeans.
Instructional Materials Service
2
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Silage crops produced for animal feeding purposes are harvested and then allowed to pass
through stages of partial fermentation. Crops harvested for silage include corn, sorghum,
soybeans, cowpeas, and clover.
Companion crops are those grown to aid the establishment and growth of other crops. Companion
crops include grasses, clover, peas, and beans.
CLASSIFICATION OF FIELD CROPS ACCORDING TO SEASON OF GROWTH
Instructional Materials Service
3
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
In the United States, two distinctive seasons exist for field crop growth. These two seasons
include warm season and cool season. Warm season crops are grown during the spring and
summer and are not adapted to cooler temperatures. Typically, these crops require irrigation for
optimal growth. Cool season crops are very resistant to cool temperatures. These crops grow
during the fall and winter and are toler- ant to freezing temperatures.
Figure 2 shows the production regions in the United States of selected warm and cool season
agronomic crops. Warm season crops include cotton, tobacco, field peas, sorghum, and citrus
fruits. These crops require warm temperatures for growth and are usually found in the subtropical
crop belts, cotton belt, and southern part of the United States.
Cool season crops include wheat, oats, barley, potatoes, and rye. These crops require cool
temperatures for optimal growth. Areas that typically grow these crops include the wheat belts,
corn belt, and hay and dairy regions of the United States.
CLASSIFICATION OF FIELD CROPS ACCORDING TO LIFE SPAN
Annuals are plants that complete their life cycle in one year. They grow, mature, produce seed,
and die in a single growing season. Annuals reproduce from seeds. Summer annuals such as corn,
beans, peas, and sorghum are planted in the spring and harvested during the summer or early fall.
Winter annuals such as winter wheat, winter peas, and vetch are planted in the fall. They mature,
produce seed, and die by the following summer.
Biennials complete their life cycle in two growing seasons. During the first season they produce
vegetative parts and store food. The plants use the stored food in the second season of growth for
flower and seed formation. After the plants mature and produce seed, they die. Examples of
biennials are sweet clover, cabbage, beets, and carrots.
Instructional Materials Service
4
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Perennials grow for more than two growing seasons. Most perennials mature after the first
growing season’s growth, but do not produce flowers until the following season or later.
Perennial crops include white clover, bermudagrass, and lespedeza.
BINOMIAL CLASSIFICATION SYSTEM
Taxonomy is the science of classifying and naming plants. Botanical classification aids
taxonomists, agronomists, and agriculturists in identifying plants and understanding plant
relationships based on similarities and differences found in their structures.
Taxonomists have identified and classified about 300,000 plant species. Over one half of those
are dicot plants. To prevent confusion and false identification, taxonomists use botanical names to
identify plants universally. Plant names are derived from Latin descriptions approved by a
committee of plant taxonomists. Carl Linnaeus, a Swedish botanist, developed the presently used
botanical classification of plants in 1753. Table 2 shows the botanical classification of two
common field crops, dent corn and alfalfa.
If no botanical classification system existed for identifying plants, many different plant species
would carry one common name. For example, all clovers would be identified as clover, although
crimson clover is a winter annual and sweet clover is a biennial. Classification is very important
in preventing confusion among scientists and farmers.
USE OF THE BINOMIAL CLASSIFICATION SYSTEM IN NAMING PLANTS
The entire botanical classification is not required in the identification of a plant by its scientific
name. The genus, species, and cultivar names are sufficient to properly identify a plant. For
example, the scientific name of a purple flower called alfalfa is Medicago (genus) sativa (species)
L. (cultivar). Sometimes the species name corresponds to a person’s first name and the genus to
the person’s surname.
Instructional Materials Service
5
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Species may be sub-divided into cultivars. Important information to remember about a cultivar
includes:



A cultivar is developed by a plant breeder; other classifications are not.
A cultivar is a rank within a species.
A cultivar is distinguished by a capitalized name before the common name of the species.
For example, Triumph is a cultivar of a wheat species; thus the proper common name is
Triumph wheat.
FOUR PLANT KINGDOMS
Thallophytes
Thallophytes are plants without stems, roots, or leaves. These plants include algae, fungi, and
bacteria.
Algae These plants contain no chlorophyll. An example of this type of plant is the scum found
floating on the surface of stock ponds.
Fungi These plants also contain no chlorophyll. Fungi are either beneficial or harmful. Common
examples of these simple, non-green plants include molds, mildews, yeast, mushrooms, smuts,
and ringworm.
Bacteria These are microscopic, one-cell organisms. Bacteria can be harmful or beneficial. The
types of bacteria that live in plant root nodules and transform nitrogen from the air to nitrogen
within the soil are beneficial bacteria. Other beneficial bacteria liberate plant nutrients by rotting
plant residue.
Figure 3. Examples of Plants with Each Phylum of the Plant Kingdom
Instructional Materials Service
6
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Bryophytes
Bryophytes are non-flowering plants that have no roots. Most Bryophytes also have no stems or
leaves. Bryophytes are more specialized than Thallophytes and include nonvascular plants such
as liverworts and mosses.
Pteridophytes
Pteridophytes are plants that include ferns, horsetails, and clubmosses. Ferns in this division are
grouped with the Tracheophytes or vascular plants.
Spermatophytes
Spermatophytes are highly-developed plants that produce seeds or fruit after fertilization takes
place in the flowers. Spermatophytes include all field crop plants. They are also called vascular
plants or Tracheophytes because the vascular vessels transport water and nutrients to the plant
roots, stems, and leaves. The remainder of this topic relates to this plant division.
TWO SUBPHYLUMS OF SEED-PRODUCING PLANTS (SPERMATOPHYTES)
The phylum of spermatophytes consists of two subphylums: gymnosperms and angiosperms.
Gymnosperms
Gymnosperms produce seeds not enclosed in ovaries. Therefore, they are said to have “naked
seed.” Gymnosperms include evergreen, woody plants such as pine, fir, and spruce trees.
Angiosperms
Angiosperms include flowering plants. This subphylum includes all field crops. Angiosperm
flowers pro- duce seeds enclosed in ovaries. Monocotyledons and dicotyledons are two classes of
angiosperms that include the seed-producing plant families.
Instructional Materials Service
7
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Monocotyledons
A monocotyledon plant has a single cotyledon or seed leaf. Monocot plants include the grass
family (Gramineae) consisting of all cereal crops and about three-fourths of cultivated forage
crops.
Two important monocotyledon families are:


The grass family (Gramineae) includes millet, corn, wheat, barley, rye, rice, oats, and
other cereal grains.
The lily family (Liliaceae) includes lilies, onions, tulips, and garlic.
Dicotyledons
A dicotyledon seed has two cotyledons or seed leaves. Dicotyledon plants include six important
families.






The legume family (Fabaceae) includes beans, peas, peanuts, vetches, lespedeza, alfalfa,
clovers, soybeans, and kudzu.
The nightshade family (Solanaceae) includes white potatoes, tobacco, peppers, eggplants,
and ground cherries.
The mustard family (Brassicaceae) includes turnips, kale, rutabaga, cabbage, cauliflower,
brussels sprouts, radishes, watercress, and mustard.
The morning glory family (Convolvulaceae) includes morning glories, sweet potatoes,
and dodder.
The mallow family (Malvaceae) includes cotton and okra.
The rose family (Rosaceae) includes ornamental roses, peaches, almonds, apricots, pears,
apples, plums, and strawberries.
DISTINGUISHING FEATURES OF MONOCOTS AND DICOTS
A comparison of monocot and dicot plant structures reveals differences in their characteristics.
This differentiation between monocots and dicots is useful in identifying various field crops.
Instructional Materials Service
8
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Roots
Most monocots have a fibrous root system, whereas most dicots have a taproot system. Figure 5
illustrates the difference between these two types of root systems.
Figure 5. Comparison of Fibrous and Taproot Systems
Stems
The vascular system within a monocot stem is asymmetrical. The vascular bundles usually lack a
definite arrangement in the stem. Monocot stems lack a vascular cambium. For this reason,
monocots never become “woody” in the true sense.
Vascular bundles in dicots are symmetrically arranged together in a ring or circle system in the
stem. The cambium layer is also located in a ring around the vascular bundle. A dicot stem can be
either woody or non-woody.
Instructional Materials Service
9
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Leaves
The primary structures of a monocot leaf include the blade, and a sheath that envelops the stem.
Leaves occur in two alternate rows on the stem and attach to the stem at nodes. The main veins in
the leaves are parallel to each other.
A dicot’s leaves are net-veined. Secondary veins branch from the primary midrib. A simple leaf
has a one- piece blade. A compound leaf has many leaflets that join at the base of the leaf stalk
(petiole). Appendages or stipules at the base of the leaf stalk occur on some dicots.
Figure 6. Comparison of Monocotyledon-Grass Leaf and a Dicotyledon-Legume Leaf
Instructional Materials Service
10
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
Flowers
A monocot’s petals and sepals are usually arranged in multiples of three. That is, three petals and
three sepals per flower.
In grasses, flower parts have a compact or open inflorescence. A perfect flower usually is
arranged in a spikelet, having a pair of bracts or glumes at the base. Stamens may vary in number,
but three stamens are most common. Bracts (palea and lemma) help support the stamens.
A dicot’s petals, sepals, and other parts are arranged on flowers in multiples of four or five.
Stamens and pistils (stigma, style, and ovary) have different arrangements. Flowers are arranged
butterfly-like as in leguminous field crops. In most clovers, flowers are arranged in heads. In
alfalfa, flowers are arranged in spike-like racemes. A typical legume flower may have five sepals
and ten stamens.
Figure 7. Comparison of Monocotyledon and Dicotyledon Flowers
ACKNOWLEDGEMENTS
Kelly Coleman, Graduate Assistant, Department of Agricultural Education, Texas A&M
University, researched and developed this topic.
Keith Zamzow, Curriculum Specialist, Instructional Materials Service, Texas A&M University,
edited and reviewed this topic.
Vickie Marriott, Office Software Associate, Instructional Materials Service, Texas A&M
University, edited and prepared the layout and design for this topic.
Christine Stetter, Artist, Instructional Materials Service, Texas A&M University, prepared the
illustrations for this topic.
Instructional Materials Service
11
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
REFERENCES
Bishop, Douglas, et al. Crop Science and Food Production. Dallas, TX: McGraw-Hill, Inc.
Poincelot, Raymond P. Horticulture: Principles and Practical Applications. Englewood Cliffs,
NJ: Prentice-Hall, Inc.
Janick, Jules, et al. Plant Science: An Introduction to World Crops. San Francisco, CA: W. H.
Freeman and Company. for Dummies. IDG Books Worldwide, Inc., 1997.
GLOSSARY OF TERMS
Agricultural producer - A person who cultivates land or crops or raises animals or fish.
Agronomist - An expert in soil management and field-crop production.
Botany - A branch of biology dealing with plant life.
Chlorophyll - The green photosynthetic pigment found in the chloroplasts of plants.
Inflorescence - The pattern of arrangement of flowers on a stem.
Irrigate - To supply land with water by artificial means.
Life cycle - The series of stages in form and functional activity through which an organism
passes.
Midrib - The primary or central vein of a leaf.
Node - The point on a stem where a leaf attaches.
Pistil - One of the ovule bearing structures in an angiosperm that comprises the innermost whorl
of a flower.
Spikelet - One of the small, few-flowered, bracted spikes that make up the compound
inflorescence of grasses.
Stamen - The pollen-producing male organ of a flower that consists of an anther and a filament.
Stipule - A pair of appendages located at the base of a leaf.
Taxonomist - A person who classifies organisms in an ordered system indicative of natural
relationships.
Vascular cambium - A thin, formative cell layer between the xylem and phloem of most vascular
plants that gives rise to new cells and is responsible for secondary growth.
Vascular plant - A plant having a specialized conducting system that includes xylem and phloem.
Instructional Materials Service
12
www.myimsservices.com
Plant Recognition: Classification and Identification of Field Crop Plants
1.
TOPIC ACTIVITIES
List several foods you have eaten today that contain any of the field crops classified
according to use.
2.
Why do you think people need to plant emergency crops?
3.
Why are sudangrass, rye, and millet used as emergency crops?
4.
In what area of the United States do you live (west, midwest, south, east, etc.)? What
types of crops are grown in your region? List environmental, climatic, and seasonal
variables that affect why farmers in your region grow the crops that you listed.
5.
What language does the taxonomic classification system use to label organisms such as
corn and alfalfa? Why do you think Carl Linnaeus chose this language to classify all
living things?
6.
Why do plant breeders and others develop further classification systems such as
cultivars?
7.
Define and explain the importance of xylem and phloem.
8.
Who was Carl Linnaeus? Why did he invent a system to classify plants and animals?
ADVANCED ACTIVITIES
1.
Find examples of Thallophytes, Bryophytes, Pteridophytes, and Spermatophytes within
your neighborhood.
2.
Using the encyclopedia, Internet, or other sources, explain the function of root hairs.
3.
Using the encyclopedia, Internet, or other information sources, compile a list of various
horticultural plants that are members of the Rosaceae family. What characteristics do
they all have in common?
4.
Make a list of plant scientific names (genus, species). Identify the origin or meaning of
the names.
Instructional Materials Service
13
www.myimsservices.com