Chapter 36 – Detailed Review
Plants exhibit indeterminate growth that means they keep on growing throughout their lives.
36.1: Plant Forms: Themes with Many Variations
Plants use light energy (photons), CO from air and water (electron source) from
soil to make carbohydrates.
Plants also use water to maintain normal pressure and volume by filling their
Plants also use nitrogen, potassium, magnesium and phosphorus to make
macromolecules like nucleic acid, enzymes and phospholipids.
Plants use two basic systems to get the resources needed for photosynthesis.
• Root System: underground, anchors plant and takes in water and ions
• Shoot System: aboveground, harvest light and CO from air to make
• Usually, the root and shoot system are connected by vascular
Herbaceous plant (herb): seed plant that lacks wood and has short lived
The Root System includes:
• Taproot: vertical section of underground root system
• Lateral root: horizontal looking sections of underground root system
• Diversity on 3 levels: morphological diversity, phenotypic plasticity
(changes in individual root system over time) and modified roots for
• Root systems are diverse in shape and size
• In prairie grassland ecosystems, grasses and herbaceous plants have
root systems that are perennial (live for many years). If the
aboveground portion dies in fire, winter or dry season, the plant can
send up a new shoot system. o Root systems of prairies plants that live side by side can be very
Prairie grass have fibrous root systems
Prairies rose has a thick taproot that can store starch
Different plants have different root systems that penetrate
the ground at different depths. The tips of the roots are
where the most water and nutrient absorption occurs.
• Natural Selection has favoured diversity in root systems among
species that live in the same area to minimize water and
o Diversity in root systems of prairie plants has 2 important
Different plant species can co-exist in the same area
with less competition for soil resources since each type of
root system is specialized in acquiring resources from
different regions of the soil
Most individuals can withstand water stress during
Phenotypic Plasticity: changes in individual root or shoot system
over time, depending on environment conditions that change
throughout the course of time
Spruce trees that grow in wet soil which lacks oxygen have shallow root
systems and the same tree growing in drier soil extends several meters
deep into the ground.
o Even genetically identical individuals have different looking
root systems if growing in different types of environment
Roots actively grow in areas where resources are abundant and
die back or do not grow in areas where resources are lacking or
Adventitious root: root that develops from the shoot system instead of the
root system Prop roots of corn brace the plant in windy weather
Mangroove plant grows in deoxygenated swamps but their root systems
can conduct gas exchange through pneumatophores and grow
upward instead of downward
The Shoot System
Consist of one or more stems – vertical aboveground structures
Nodes: located on stems where leaves are attached
Internodes exist between nodes
Leaves: appendages that extend laterally from the stem and consist of
Axillary bud: a bud forms between a leaf and stem and may develop into a
branch if conditions are appropriate
Apical bud: a bud at the tip of a bud or stem where growth extends the length
of the stem or branch
The shoot system is a repeating series of nodes, internodes, leaves,
apical and axillary buds. After an initial period of growth, the plant
grows by adding more parts rather than increasing the size of each
part. Thus, the number of nodes, internodes and leaves increases as
the plant grows.
Shoot systems of different plants range in size.
In habitats where light is scarce, plants invest more energy and resources in the
growth of light gathering apparatus.
The manners in which the branches are added to the shoot system (narrow
angles, long internodes/wide angles, short internodes) affect the shape of the
individual and its ability to compete for light.
Variations in the size and shape of the shoot system are important: it
allows plants of different species to harvest light and CO at 2ifferent
locations, minimize competition and thrive in a wide array of habitat.
Shoot system also respond to variations in water, nutrient and light availability. Shoot systems can bend toward light if the plant is shaded on one side or grow
more leaves and branches in regions exposed to more light.
Shoot system grows in direction that maximizes the plant’s chance of
Extra-floral nectaries (EFN): produced by plants to attract and feed ants that
attack herbivores who feed on the plants.
• Plants respond to herbivore attack on their leaves by producing
Not all stems acquire CO an2 photons for photosynthesis.
• Enlarged Cactus stems store water and leaves are modified into spines
for plant protection.
• Stolons: aboveground modified stems that run over soil surface and
produce roots and leaves
• Rhizomes: underground stems store starch and aid in asexual
reproduction by producing a new plant at each node
• Tubers: underground swollen ends of rhizomes that store carbohydrate
• Thorn: modified stems protect plants against herbivore attacks
Large surface area is site of photosynthesis
Simple leaf has two parts:
• Blade: expanded portion of leaf
• Petiole: stalk of the leaf
Simple leaves have a blade and petiole.
Compound leaves have the blade divided into smaller leaflets.
Doubly compound leaves have leaflets divided into smaller ones. Needle – shaped leaves exist in deserts or northern habitats because
• Reduce surface area to prevent water loss through transpiration
• Less susceptible to wind damage
Leaves can be
• paired opposite to each other on a stem
• alternate on either side of the stem
• arranged in compact clusters at plant base
Different plant species arrange their leaves in different arrangements
to maximize the efficiency of the light captured.
Leaves don’t grow cont