Download Plant Adaptation to Habitats Tour

Regional Parks Botanic Garden
Plant Adaptations to Habitat Tour: Selected Plant Adaptations by Garden Section
INTRO
Tools (optional, but nice to use):
-Discovery Scope
-Spray bottle of water--from the Visitor Center, located on left side of top drawer of
docent cabinet (head docent places it by the redwood closest to the the West Gate so
everyone can use it and returns it to the cabinet after the tour.)
Introducing the Concepts of Habitat and Adaptation
Habitat
A habitat is the natural place where a plant or animal lives, which provides what the
animal or plant needs to live.
What do we (people) need to live?
(Oxygen from air, water, food, shelter)
What do plants need to live?
(Carbon dioxide from air, water, sun, and [usually] soil/substrate)
This garden is arranged in areas that represent different parts of California, and those
different parts of California have different types of habitats.
Adaptation
A characteristic of a plant or animal that makes it better able to live in a particular habitat.
GARDEN SECTIONS
Adaptations in the Redwood Section
General: Understory plants in redwood forests are adapted to low light conditions. Adaptations
include relatively large leaves for the size of the plant, leaves held horizontally to capture more
sunlight, and leaves often dark green (they contain more chlorophyll) and therefore able to
absorb and make use of limited sunlight in the shade of big trees.
Redwood sorrel (Oxalis oregana)
Adaptation to low levels of sunlight: Leaves can move from horizontal to vertical and
back in response to more or less sunlight. When the leaves are folded down (vertical),
they absorb less heat from sunlight and lose less water through transpiration because they
stay cooler.
Activity: Look for some plants in sun and some in shade.
Coast redwood (Sequoia sempervirens)
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Adaptation to summer drought: The redwood’s slick leaf surface, downward-sloping
branches, and many small downward sloping leaves allow condensed fog (of which there
is usually plenty in the summer where redwoods are native) to form drops and drip onto
the ground under the tree. This can add the equivalent 10 inches of rain per year in the
summer.
Activity: Simulate fog by spraying a redwood branchlet with a fine mist from a spray
bottle from several inches away and watch the water bead up on the leaves and drip off
onto the ground below.
Adaptations in the Sierra Nevada Section
General: Plants are adapted to winter drought and high levels of UV radiation at high elevations.
Quaking aspen (Populus tremuloides)
Adaptation to winter drought: Deciduousness helps the plant survive winter drought
when the plant is under snow (water is not available to the plant when it is frozen). The
plant loses little water when it doesn’t have leaves.
Adaptation to high levels of UV: The white, powdery coating on trunk protects the thin
bark from sunburn damage (white reflects away light).
Activity: Try to rub a little of the white powder off the trunk with your finger—choose a
very white-looking trunk for best results (and please don’t rub off a lot!).
Adaptations in the Shasta-Klamath Section
General: Plants are adapted to snow.
Engelmann spruce (Picea engelmannii—in front of visitor center)
Adaptation to heavy snow: Branches slope downward and are relatively flexible, which
causes snow to slide off rather than accumulate and break the branches.
Activity: Look at the shape of the branches and feel the slick needles.
Adaptations in the Desert–Southern California Section
General: Plants are adapted to heat and drought—they have small leaves, vertically oriented
leaves, white hairs on leaves, etc.
Cactus (For example, Opuntia by the front gate)
Adaptations to heat and drought:
1. Cacti do not have leaves (a few types of cacti have leaves very briefly when they first
start to grow in the spring, but those fall off when the weather gets warm and dry).
This reduces water loss by transpiration. Spines protect the plant from herbivory by
animals seeking food and moisture in an environment where neither is abundant.
2. Stems are flattened and green and perform the function of leaves (absorbing sunlight
and producing food for the plant through photosynthesis).
3. Succulent stems store water for the plant, which helps it survive drought.
4. Many cacti are able to grow new roots (sometimes called rain roots) very quickly
when it rains—to absorb the rainwater from the upper few inches of the soil. These
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roots will die back during dry weather, but they are not necessary to sustain the plant
and can be grown again, so they are expendable.
5. Metabolism (information from Wikipedia)—this part is probably too advanced for
3rd graders!
Photosynthesis requires plants to take in carbon dioxide gas (CO2). As they do so,
they lose water through transpiration. Like other types of succulents, cacti reduce this
water loss by the way in which they carry out photosynthesis. "Normal" leafy plants
use the C3 mechanism: during daylight hours, CO2 is continually drawn out of the air
present in spaces inside leaves and converted first into a compound containing three
carbon atoms (3-phosphoglycerate) and then into products such as carbohydrates. The
access of air [from outside the plant] to internal spaces within a plant is controlled by
stomata [like pores], which are able to open and close. The need for a continuous
supply of CO2 during photosynthesis means the stomata must be open, so water vapor
is continuously being lost. Plants using the C3 mechanism lose as much as 97% of the
water taken up through their roots in this way. A further problem is that as
temperatures rise, the enzyme that captures CO2 starts to capture more and more
oxygen instead, reducing the efficiency of photosynthesis by up to 25%.
Crassulacean acid metabolism (CAM) is a mechanism adopted by cacti and other
succulents to avoid the problems of the C3 mechanism. In full CAM, the stomata
open only at night, when temperatures and water loss are lowest. CO2 enters the plant
and is captured in the form of organic acids stored inside cells (in vacuoles). The
stomata remain closed throughout the day, and photosynthesis uses only this stored
CO2. CAM uses water much more efficiently at the price of limiting the amount of
carbon fixed from the atmosphere and thus available for growth.
Simpler version: Sun, water and carbon dioxide are the essential ingredients a plant
needs to make food for itself through a process called photosynthesis. Most plants can
only make food through photosynthesis during the day—when the sun is out. But
cacti and some other succulent plants are able to make food (photosynthesize) at
night, which is unusual compared to most plants. To get carbon dioxide into its cells
for use in photosynthesis (along with sunlight and water), a plant’s pores (also called
stomata) have to be open. But if the pores are open, water can evaporate through them
when it’s warm and cause the plant to get too dry (kind of like a person sweating a lot
but not drinking anything). Cacti have a special adaptation that allows them to open
their pores and take in carbon dioxide during the night, when it’s cooler and they
won’t lose as much water through their pores. Cacti are able to store the carbon
dioxide from the night to use for photosynthesis the next day when the sun is out.
Great Basin sagebrush (Artemisia tridentata)
Adaptations to heat and drought:
1. Small leaves have less surface area from which water can evaporate.
2. White hairs keep leaves cooler and thereby reduce transpiration—they both reflect
away sun and trap a layer of slightly more humid (moist) and cooler air next to the
leaves.
3. Compounds in leaves that have strong scents protect plant from herbivory by animals
seeking food and moisture in an environment where neither is abundant.
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Activity: Pick a leaf for each student and yourself. Look at the leaf and talk about its
color, etc. Ask students to use a fingernail to scrape the upper or lower surface of the
leaves and talk about what they notice (usually say it’s green underneath). Pass around a
Discovery Scope with a leaf positioned so the white hairs can be seen.
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Adaptations in the Valley-Foothill Section or Santa Lucia Section
General: Plants are adapted to periodic fire.
Manzanita (Arctostaphylos—many species)
Adaptation to periodic fire: Some manzanitas have a basal burl with buds that sprout after
the top of the plant has been killed in a fire (we don’t have a good example of a basal burl
at the Botanic Garden). Others resprout mainly from seeds, which are very hard and
impervious to water and can survive in the soil for many years. The heat of a fire can
crack the seeds in the soil, enabling them to absorb water, germinate, and grow into new
plants when the rains come.
Activity: Look for a plant with fruits on it to show the hard seeds.
Adaptations in the Sea Bluff Section
General: Plants are adapted to sunny, windy conditions with features similar to desert plants:
Low-growing plants with small, often vertically oriented leaves, sometimes with white powdery
coatings or hairs (all of which reduce the plant’s exposure to sun or wind).
Dudleya (Dudleya sp.)
Adaptations to drying sun, wind, summer drought:
1. The white, powdery coating on the leaves reflects away sunlight and reduces
transpiration (leaves stay cooler and therefore lose less water).
2. Succulent leaves store water, which helps the plant survive drying conditions and
summer drought.
Activity: Touch a small area of a Dudleya leaf to feel the white powder, and notice the
thickness of the succulent leaf, which is storing water in its tissues.
Adaptations in the Rainforest Section
General: Adaptations are similar to those of Redwood Section plants (low light) and include
relatively large leaves for the size of the plant, leaves held horizontally to capture more sunlight,
leaves often dark green (more chlorophyll) to absorb and make use of limited sunlight.
Skunk cabbage (Lysichiton americanus)
Adaptation to low light levels: Very large, deep green leaves that can capture the limited
sunlight in the understory of a dense forest.
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