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Apical meristem – This top most bud on the plant is the main growing point from
which new leaves are initiated and produced. It is enclosed in the leaf of
the youngest developing leaf. Axillary meristems – These “lateral” buds are present at each node above the soil
surface. They normally remain dormant, but growth can resume from these buds
if the apical meristem is destroyed. Cotyledons – These seed leaves are present in the embryo before
germination. They are the food source for germination processes and also
support the plant through photosynthesis until the first true leaves are formed.
The cotyledons must be pulled through the soil by the hypocotyl during the
emergence process. Epicotyl - The part of the stem
above the cotyledons. Hypocotyl - The part of the stem below the cotyledons. During germination
and emergence it forms an arch and elongates to pull the cotyledons through
the soil. The arch straightens when the epicotyl senses light at the soil
surface and the cotyledons unfold to intercept sunlight for photosynthesis. Radicle – This embryonic root is present in the seed and grows to form
the root system. The sunflower plant relies on this root system, which grows
to depths greater than 6 feet below the soil surface, for the water and
nutrients needed to sustain plant growth. True leaves –The leaves that form after the cotyledons have unfolded. At
first they appear to form in opposite pairs on the stem, but they gradually
begin to alternate up the stem as more leaves are added. Eventually more than
30 leaves may be formed. |
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