Fruits
and Seeds
Fruits are the ripened
and seed-bearing ovaries of flowers. Fruits are nearly
as varied in color, form, size, texture, and number as
are flowers, making them valuable tools in plant
identification.
Botanists use the term
"fruit" in a much broader way than does the
layperson. Fruits are divided into two large categories:
dry fruits and fleshy fruits.
Dry fruits -
generally grey, brown, or another dull color, with a
very thin and dry ovary wall, so that the food is
largely confined to the seeds. These may be further
subdivided based on the number of seeds and whether the
fruit remains closed at maturity ( indehiscent )
or opens naturally ( dehiscent ).
- Achene - small,
hard, indehiscent, one-cavitied, one-seeded fruit
with a thin, almost inseparable wall, as in Helianthus
annuus (sunflower).
- Samara -
indehiscent, one or two-seeded winged fruit, as in Acer
rubrum (red maple).
- Nuts -
hard-shelled, usually one-seeded, indehiscent
fruits, such as Juglans nigra (black walnut)
or Carya illinoinensis (pecan).
- Grain or Caryopsis -
one-seeded, indehiscent fruit of most grasses,
including the cereals. The enclosed seed is almost
inseparable from the enveloping ovary wall. This
fruit is little more than a seed for all practical
purposes.
- Capsule -
dehiscent fruit composed of two or more carpels,
generally with several or many seeds in each carpel,
as in Gossypium spp. (cotton).
- Silique -
several-seeded fruit with two carpels which pull
away from the central partition at maturity, as in Iberis
odorata (candytuft) and Brassica spp.
(mustard).
- Silicle - a
silique which is wider than long, such as in Lepidium
virginicum (peppergrass).
- Legume - pod
formed from a simple pistil, dehiscent along both
sides, as seen in Pisum sativum (pea) and Senna
alata (candle bush).
- Follicle -
several-seeded fruit formed from a single carpel and
splitting open along one side only. There may be two
or more follicles produced by each flower, as in Mandevilla
splendens (pink allamanda) and Asclepias spp.
(milkweed).
Fleshy Fruits -
are usually juicy and brightly colored, contrasting with
their background to make them more noticeable to
animals, who are responsible for their dispersal. All
fleshy fruits are indehiscent and considerable fleshy
tissue is developed as the ovary changes into the fruit.
- Drupe -
"stone fruit", a simple fruit produced
from a single carpel, usually one-seeded, with an
outer fleshy layer of tissue called the pericarp and
an inner, heavy stony layer called the endocarp .
Examples are Prunus persica (peach), Cocos
nucifera (coconut), Mangifera indica (mango)
and Olea europaea (olive).
- Berry - one or
more carpels developed within a thin covering, very
fleshy within, with the seeds embedded in the common
flesh of a single ovary, such as Psidium guajava (guava),
Lycopersicon esculentum (tomato), and Vaccinium
spp. (blueberry).
- Pepo -
berry-like fruit of large size, with a tough or very
firm and hard outer wall (rind) which is developed
from the receptacle, such as Citrullus lanatus (watermelon),
Cucumis sativus (cucumber), and Cucurbita spp.
(squash).
- Hesperidium -
berry-like fruit of Citrus spp. (citrus) with
a thick rind with numerous oil glands, and an
interior fleshy part composed of wedge-shaped
compartments, with or without seeds.
- Pome - fruit
developed largely from the receptacle which
surrounds the carpels or inedible core parts, as in Malus
spp. (apple) and Pyrus pyrifolia (sand
pear).
- Aggregate -
fleshy fruit developed from the ovaries of a single
flower, which becomes enlarged and bears many
simple, true fruits resembling achenes or drupes, as
in Fragaria x ananassa (strawberry).
Achenes are the fruit embedded in a fleshy
receptacle.
- Multiple -
fruits derived from many closely clustered flowers,
such as in Morus spp. (mulberry) and Ananas
comosus (pineapple).
Gymnosperms -
produce seeds but not true fruits since they have no
ovary; such seeds are said to be naked and are borne on
the inside of the scales or cones, but in plants such as
Juniperus spp. (junipers) and Podocarpus spp.
(podocarpus) they are embedded in a fleshy fruit-like
organ, known as an aril.Seeds -
consist of an outer coat or wall, which is usually very
tough, hard, or woody, within which are cotyledons and
the embryo. Seeds normally have just one embryo, but
sometimes have more than one, as Citrus spp.
(citrus) and Mangifera indica (mango), which
results in two or more new plants growing from one seed.
Seeds are developed as a result of the fertilization of
the egg in the ovule of the ovary of a flower. Typically
seeds are oval or globular and range in size from
dust-like orchid seeds to the large seed of the Persea
americana (avocado), with some plants bearing seeds
of even greater size such as Cocos nucifera (coconut).
Seeds vary greatly in color, texture, longevity, and
methods of dispersal. Some of the modifications of seeds
which aid in dispersal are coverings of spines, hooks,
bristles, cotton, or plumes, or having wings and arils.
They also vary in the types and abundance of food they
contain.
Cotyledon -
these "seed leaves" are the primary leaves in
the seed. In monocotyledons, the seed contains only one
seed leaf and in dicotyledons it has two. In monocots,
such as grasses, the single cotyledon remains inside the
seed and acts as a digestive organ for the embryo.
Cotyledons of dicots are often pushed up out of the seed
at germination and reach above ground where they develop
green color and act as true leaves. In other dicots,
such as Pisum sativum (English pea), the
cotyledons remain below the surface and simply provide
stored food for the young plant.
Source: Botany
Handbook for Florida, Revised Edition, Kathleen
C. Ruppert, January 1999 -- This document is copyrighted
by the University of Florida, Institute of Food and
Agricultural Sciences (UF/IFAS) for the people of the
State of Florida. UF/IFAS retains all rights under all
conventions, but permits free reproduction by all agents
and offices of the Cooperative Extension Service and the
people of the State of Florida. Permission is granted to
others to use these materials in part or in full for
educational purposes, provided that full credit is given
to the UF/IFAS, citing the publication, its source, and
date of publication.
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