Download 9.3 Growth in Plants

9.3 Growth in Plants
Chun To Yeung, Au Yeung Hon
Indeterminate Growth
Animals and some plants will stop growing at a
specific age, when a certain size is reached, or
that a structure is fully formed. These are
known as determinate growth. Plants however,
usually have an indeterminate growth, meaning
that it will not stop growing, and cells will
continue dividing.
Roots and Shoots
In a plant, the stem and
branches that grow
upward and sideways
are parts of the shoot.
Everything underneath
are roots.
Apical Meristems
Plants grow from Meristems.
Meri(stem)s, are tissues that consists of stem
cells, and will divide to help plants grow.
Apical meristems are stem cells that are located
at the tip of the plant or branches, such that the
plant grows taller and branches grow longer.
Lateral Meristems
Lateral Meristems are stem cells that divide
and produce more xylem and phloem tissue,
which essentially thickens the roots and
stems of a plant.
Role of Mitosis in Stem Extension
Cells in meristems go through processes of
mitosis and cytokinesis to produce more
cells. These new cells absorb nutrients and
water and so increase in volume and mass.
Root and Shoot Apical Meristems
Root apical meristems are responsible for growth
of the root.
Shoot apical meristems helps the growth of the
stem and produces groups of cells that grow and
develop into leaves and flowers. With each
division, one cell remains in the meristem while the
other increases in size and differentiates as it is
pushed away from the meristem region.
Additional Meristems
Apical meristems give rise to additional
meristems.
Protoderm develops epidermises,
Procambium develops vascular tissues and
Ground meristem develops pith.
Chemical influences also determine which type
of specialized tissue arises from meristems.
To Recap:
https://www.youtube.com/watch?v=h9kCPO
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Plant Hormones affect Shoot
Growth
Hormone - Chemical message produced on one part of the
organism that have affect on the other parts
Auxins (IAA) - Hormones that have a great impact on
growth of plant
● Produced in apical meristem
● Control growth of shoot apex
● Promotes elongation of cells in stems
● Can inhibit growth at high concentrations
Plant Tropisms
Two factors that affect rate and direction of growth of
plants:
Light - Grow towards source of light - Phototropism
Gravity - Grow upward against gravity Gravitropism
Both directed by PIN3 proteins that transport auxin
from cell to cell
Intracellular Pumps
Phototropism:
Intracellular
Gravitropism:
https://www.youtube.com/watch?v=5JXm1U
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