Transcript Plant Structure and Function

Plant Material Maintenance, chapter 2 in the text
Acer saccharum
Betula nigra
Viburnum dentatum
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Crown: the branches, twigs and leaves of a
tree or shrub.
Shoot: a young, actively growing stem.
Bud: an unexpanded shoot or flower (a
dormant meristem)
◦ Leaf (Vegetative)
◦ Flower
◦ Mixed
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Meristems:
Places in plants
where cell division
is occurring.
◦ Apical meristems
are found in shoot
tips and root tips.
AM cause shoot and
root lengthening.
◦ Vascular cambium
causes diameter
growth in stems and
roots.
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Growth: the amount of growth experienced by an
individual shoot depends on the rate of and
duration of cell division and expansion.
Varies by species.
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Short (3-4 weeks) growth flush in the spring.
◦ Ex: Coniferous Evergreen plants and many
deciduous plants.
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Several growth flushes over a growing
season.
◦ Ex: Monterey Pine and many species of oak.
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Growth continues as long as conditions are
favorable.
◦ Ex: Sweet Gum, Redwood, and Sugar Maple.
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Photosynthesis:
Light
Water
Carbon Dioxide
Chlorophyll (a green pigment
found in leaves)
Glucose (sugar; carbohydrate)
Oxygen
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Holly leaves have
a thick, waxy
cuticle.
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Anchorage.
Absorption of water and mineral nutrients.
Storage of food reserves.
Synthesis of organic regulatory compounds.
•Tree roots extend radially in every
direction to a distance equal to at
least the height of the tree (assuming
no physical barriers) and grow
predominantly near the soil surface.
•Typically 90% of all roots, and
virtually all the large structural
supporting roots, are in the upper
2-3 feet of the soil. This includes the
small, feeder roots.
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Taproots are
common on the
dicots.
Fibrous root
systems are
common on the
monocots.
fibrous root system
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Translocation of water, nutrients, and sugars.
◦ Xylem: transports water and dissolved nutrients.
◦ Phloem: transports sugars
◦ Movement is from “source to sink”; that is from
areas of high concentration to areas of low
concentration.
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Stems support the leaves and fruit.
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Roots that develop from newly organized
meristems forming in stems, leaves, and
other plant parts.
Adventitious roots
developing from the leaf
petiole of Peperomia.
Adventitious roots
developing from the stem of
a Coleus cutting.
Adventitious roots forming on an
Iris corm.
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Photosynthesis
Respiration
Transpiration
light
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Photosynthesis is occurring primarily in the
leaves and green stems.
Respiration is occurring in all of the living
cells of a plant; leaves, stems, and roots.
Oxygen
Carbohydrates (sugars)
Carbon dioxide
Water
Heat
Chemical energy (ATP)
Light and chlorophyll
Water
Starch
Carbon
dioxide
PHOTOSYNTHESIS
Sugars
Pectin
Cellulose
Lignin
Fats
Oxygen
Proteins
Soil Minerals
Absorbed with water
Enzymes
Pigments
Hormones
Carbon
dioxide
RESPIRATION
Vitamins
Water
HEAT
ATP
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Soil pore space is filled with water.
No oxygen in the pore space.
Without oxygen the roots will die.
Without roots the plant can’t absorb water.
◦ Low areas
◦ Soil compaction
◦ Burm up the soil or drain the planting hole.
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On sunny, warm days the sun warms up the leaf
surfaces.
The water in the cells of a leaf begins to evaporate.
Water vapor collects in the spongy mesophyll tissue of
the leaf.
The water vapor moves out of spongy mesophyll,
through the open stomata, and into the drier air
surrounding the leaf.
As water evaporates from the spongy mesophyll, new
water molecules are delivered to the leaf through the
xylem in leaf veins.
Transpiration is a “pulling” force drawing water up the
stem xylem and into the leaves.
•The rate of transpiration is
affected by the following 3 things:
•Humidity; during dry, less
humid days the rate of
transpiration increases.
•Temperature; the rate of
transpiration is greater on hot
days than on cooler, cloudy
days.
•Wind; the rate of transpiration
is greater on windy days than
calmer days.
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Phototropism: a shoot will always grow
towards a light source.
Geotropism: roots always grow down in
response to gravity.