Principles of Plant Genetics and Breeding

78 CHAPTER 5
may be classified into groups. The common groups are
as follows.
1 Erect. Erect plants can stand upright without physical
support, growing at about a 90° angle to the
ground. This feature is needed for mechanization
of certain crops during production. Plant breeders
develop erect (bush) forms of non-erect (pole) cultivars
for this purpose. There are both pole and bush
cultivars of crops such as bean (Phaseolus vulgaris L.)
in cultivation.
2 Decumbent. Plants with decumbent stem growth
form, such as peanuts (Arachis hypogea), are extremely
inclined with raised tips.
3 Creeping (or repent). Plants in this category, such
as strawberry (Fragaria spp.), have stems that grow
horizontally on the ground.
4 Climbing. Climbers are plants with modified vegetative
parts (stems or leaves) that enable them to wrap
around a nearby physical support, so they do not have
to creep on the ground. Examples are yam (Dioscorea
spp.) and ivy.
5 Despitose (bunch or tufted). Grass species, such as
buffalograss, have a creeping form whereas others,
such as tall fescue, have a bunch from and hence do
not spread by horizontal growing stems.
Agronomic use
Crop plants may be classified according to agronomic
use as follows:
1 Cereals: grasses such as wheat, barley, and oats
grown for their edible seed.
2 Pulses: legumes grown for their edible seed (e.g.,
peas, beans).
3 Grains: crop plants grown for their edible dry seed
(e.g., corn, soybean, cereals).
4 Small grains: grain crops with small seeds (e.g.,
wheat, oats, barley).
5 Forage: plants grown for their vegetative matter,
which is harvested and used fresh or preserved as
animal feed (e.g., alfalfa, red clover).
6 Roots: crops grown for their edible, modified
(swollen) roots (e.g., sweet potato, cassava).
7 Tubers: crops grown for their edible, modified
(swollen) stem (e.g., Irish potato, yam).
8 Oil crops: plants grown for their oil content (e.g.,
soybean, peanut, sunflower, oil palm).
9 Fiber crops: crop plants grown for use in fiber
production (e.g., jute, flax, cotton).
10 Sugar crops: crops grown for use in making sugar
(e.g., sugarcane, sugar beet).
11 Green manure crops: crop plants grown and
plowed under the soil while still young and green,
for the purpose of improving soil fertility (e.g.,
many leguminous species).
12 Cover crops: crops grown between regular cropping
cycles, for the purpose of protecting the soil
from erosion and other adverse weather factors
(e.g., many annuals).
13 Hay: grasses or legume plants grown, harvested,
and cured for feeding animals (e.g., alfalfa,
buffalograss).
Adaptation
There are also other operational classifications used by
plant scientists. For example, plants may be classified on
the basis of temperature adaptation as either cool season
or warm season plants.
1 Cool season or temperate plants. These plants,
such as wheat, sugar beet, and tall fescue prefer
a monthly temperature of between 15 and 18°C
(59–64°F) for growth and development.
2 Warm season or tropical plants. These plants, such
as corn, sorghum, and buffalograss, require warm
temperatures of between 18 and 27°C (64–80°F)
during the growing season.
Additional classification of horticultural
plants
Whereas some of the above operational classifications
are applicable, horticultural plants have additional classification
systems. These include the following:
1 Fruit type:
(a) Temperate fruits (e.g., apple, peach) versus
tropical fruits (e.g., orange, coconut).
(b) Fruit trees, which have fruits borne on trees
(e.g., apple, pear).
(c) Small fruits, generally woody perennial dicots
(e.g., strawberry, blackberry).
(d) Bramble fruits, non-tree fruits that need physical
support (e.g., raspberry).
2 Flowering (e.g., sunflower, pansy) versus foliage
(non-flowering, e.g., coleus, sansevieria) plants.
3 Bedding plants, annual plants grown in beds (e.g.,
zinnia, pansy, petunia).
4 Deciduous trees (shed leaves seasonally) versus evergreen
plants (no leaf shedding).