Download Seeds and germination - wheat

5 Wheat
Seeds and germination - wheat
‘Seed’ structure. The wheat grain is really a fruit, containing one seed. The thin ovary wall is
fused with the testa and does not interfere with germination.
Germination The fruit absorbs water, swells, and a radicle bursts through the fruit wall. Shortly
after, other radicles emerge from the fruit, developing equally so that there is no main root. Root
hairs grow on the upper regions. The plumule grows straight up and through the fruit wall, but
the growing point and first leaves are protected by a sheath, the coleoptile, with a hard, pointed
tip. Once above the soil the first leaves burst out of the coleoptile which remains as a sheath
round the leaf bases.
The cereals, maize, wheat, barley, oats etc. are all monocotyledons, having only one cotyledon
in the seed. Unlike the dicotyledonous plants, the single cotyledon does not contain a store of
food. The food reserve necessary for germination is stored in the endosperm, mainly as starch.
When the grain absorbs water, enzymes are activated. These enzymes digest the starch in the
endosperm to soluble sugar. The cotyledon absorbs the sugar and passes it to the rapidly growing
radicle and shoot.
region of
attachment to
stalk
position of
plumule
endosperm
fruit wall and
testa
cotyledon
plumule
position of
radicle
Wheat grain
radicle
(a) external
appearance
(b) longitudinal section
first leaf
plumule more
conspicuous
beneath fruit wall
fruit wall
splits
coleoptile
breaks open
plumule in
sheath
(coleoptile)
root hairs
radicle
emerges
more roots
appear
roots
Germination of wheat
© D.G. Mackean