Agriculture Reference
In-Depth Information
the seed is a means of protecting against extreme
conditions of temperature and moisture, and is thus
often the
overwintering
stage
. The seed, together
with the fruit, may also enable the embryo to be
dispersed away from the parent plant and may have
dormancy mechanisms which prevent germination
until conditions are favourable.
Seed structure
The basic structure of a dicotyledonous seed is shown
in Figure 8.12. The main features of the seed are:
X
The embryo
. In order to survive, the seed must
contain a small immature plant protected by a seed
coat. The embryo consists of a
radicle
, which
will develop into the root of the seedling to take
A
seed
is the structure that develops from the
ovule after fertilization. A
fruit
is formed from
the ovary wall usually following fertilization and
encloses the seed.
(a)
Plumule
(b)
Epicotyl
Hypocotyl
Radicle
Hilum
Micropyle
Cotyledon (1 of two)
Testa
Figure 8.11
Seeds: a range of species. Top: runner
bean; left to right: leek, artichoke, tomato, lettuce,
Brussels sprout, cucumber, carrot, beetroot
Figure 8.12
Dicotyledonous seed structure: (a)
germinating
Phaseolus coccineus
(runner bean) seed
showing developing radicle; (b) long section of a
Phaseolus vulgaris
(French bean) seed
