Download Grade 4 Performance Task

Grade 3 Performance Task: Up the Beanstalk!
Content Connections
Assessment Criterion:
•
Understanding of Basic Concepts
Overall Indicator
The student
• identifies the major parts of plants
• describes changes in a plant’s life cycle
Part A: Major Parts of Plants
Key terms: root, stem, leaf, flower
Flower
Leaf
Stem
Key Concepts:
a) Root
Kinds of Roots
The first growth from a germinating seed to enter the soil and push downward is
the primary root. Soon branch roots grow out from the primary root, and these in
turn may produce further branching. All branch roots are referred to as secondary
roots.
Roots do not always originate, however, from a seed or as branches of a primary
root. Some roots spring from stems that bend over and come in contact with the
ground as in tomato plants, or from the ends of stem cuttings that are kept moist,
as with geraniums and other house plants. African violets strike roots from their
leaves. All such roots, that arise from plant organs other than roots, are called
adventitious roots.
A: Tap root of a dandelion
B: Fibrous root of grass
C: Adventitious roots of English Ivy
D: Surface runner root of strawberry
Root Systems
When a primary root grows with more vigour than its branch roots, the result is a
large, main root axis, or tap root. Plants such as the dandelion, sweet clover, and
alfalfa have tap roots that are slender and go deep to secure water. Since these
plants do not need to compete with the shallower-rooted plants that draw water
from near the surface, they usually look fresh and green in very dry weather. In
plants such as carrot, radish, and parsnip, the tap root becomes much enlarged
and serves for storage of food and water. With many plants the primary root at an
early stage slows down its growth, while secondary and adventitious roots grow
rapidly to produce a mass of fine, branching root threads, termed a fibrous root
system. Grasses and grains, and the common buttercup have fibrous roots. Root
functions. The root is primarily an organ for absorbing water and dissolved
minerals from the soil. The extent to which it spreads its finer rootlets in search of
water is almost incredible. In one study of root systems, a single plant of winter
rye grass, in a period of four months, developed over three hundred and fifty
kilometers of roots.
Since absorption occurs only at the root tips, another function of roots is that of
conducting the absorbed water toward the main part of the plant. The tubes for
this purpose are microscopic in diameter but numerous, and lie in bundles within
the core of each rootlet.
A root also anchors a plant in one place, and if the anchorage is firm, it permits a
plant to stand erect. A root system that lives over winter serves, too, as a
storehouse of food for early new growth the following year. Food storage is true
of fibrous as well as tap root systems.
b) Stem
The first evidence that garden seeds have germinated is the appearance above
ground of a shoot. The shoot (with most plants) at first bears a pair of "seed
leaves" and a growing point bud which rapidly expands into a stem bearing
leaves and flowers. The stem has definite nodes, more or less evenly spaced,
from which the leaves grow out. The crotch between leaf and stem is known as
the axil of the leaf. The leaf axil is the customary position of growing points and
buds, and therefore the place from which branch stems and flowers arise.
Likewise, it is at or near the nodes that adventitious roots may be found, and also
the buds on shrubs and trees.
Kinds of Stems.
Annual plants produce stems that are usually soft, juicy, and subject to wilt or
collapse. They are called herbaceous stems. Similarly, many perennial plants
have above-ground parts that regularly die at the end of each growing season;
their one-season stems are also herbaceous. Shrubs and trees, on the other
hand, build up in their stem systems a large amount of tough, fibrous,
strengthening tissue that lasts from year to year. Their stems are described as
woody. In addition to woody tissue, every tree and shrub has some delicate
growth tissue called cambium which remains alive over winter despite low
temperatures, and each year adds new growth layers to both wood and bark.
Trees such as the Douglas firs of British Columbia may live for hundreds of years
and acquire a trunk diameter of several feet.
Stem Habits
Stems show a variety of growth habits. They may stand stiffly erect, as in mullein,
wheat, and oats, or spread a broad crown as in elm and maple; or simply recline
oh the ground. Vine plants like cu- cumber and melon that are rooted in one spot
and send a sprawling stem system over the ground have trailing stems.
Strawberry and silverweed, that send forth slender stems that take root at each
node and in this way establish their hold anew, are called creeping stems. Some
stems, too weak to rise above ground-level otherwise, send out tendrils for
attachment to firm supports to become climbing stems, as in grape, pea, Virginia
creeper, and ivy. Whatever its method, each stem type succeeds admirably in
spreading its leaves to the best advantage for maximum sunlight.
Stem Functions
The stem has two main functions; first, to support the leaves, flowers and fruits,
raising them into a position where they are able to secure favourable light; and
second, to provide the channels for conduction between root and leaves. Water
absorbed by the root is conducted upward through certain tissues to the leaves,
while food made in the leaves is conducted downward through other stem tissues
to the root.
In addition, the stem produces the buds for new growth. Shrubs and trees, during
the progress of one season, are busy forming the winter buds that make possible
such prompt and rapid growth of shoots the following spring. To a limited extent,
perennial stems store food over winter, and in some cases, if adventitious roots
form readily, stems serve to reproduce a plant, as with willow.
c) Leaf
Parts of a Leaf
Most of a plant's highly valuable green tissue is built into its leaves, which
become broad, thin organs to display this tissue most effectively to the light. The
thin broad expanse of the leaf is its blade, usually held at the end of a slender
leaf-stem called a petiole. A complete leaf has, in addition, a pair of smaller, leaflike bracts at the base of the petiole where it joins the stem. These bracts, called
stipules, are not essential to a leaf, and are found on rather a small number of
plants.
Kinds of leaves
A simple leaf is one in which the blade is all in one piece. It may be lobed,
notched, or deeply divided almost to its midrib, and still be considered a simple
leaf. If the blade is divided into distinct, separated areas, however, the leaf is
compound. The separated areas, called leaflets, may be attached to the sides of
the midrib, in which case the leaf is pinnately compound (from its resemblance to
a feather, or "pinna"); or the leaflets may be attached in spread-out fashion at the
end of the petiole (resembling the spread fingers of a hand), and the leaf is then
said to be palmately compound. We find examples of pinnate compounding in
the fern, the walnut, and the ash. The horse chestnut and poison ivy have
palmately compound leaves.
A: “Feather” Leaf
B: “Palm” Leaf
C: “Vein” Leaf
Duration of Leaves
Annual plants have leaves that function for only a few weeks or a few months.
This is true also of most of our trees and shrubs, which are termed deciduous
because they shed their leaves each autumn. Leaves that continue to function
beyond the year in which they are formed are called evergreen. Although some
evergreens are broad-leaved, as in winter- green, azalea, and a few ferns, the
better- known ones have needle-like leaves, like pines, spruces, and hemlocks.
The cedars have scale-like leaves, close-ranked and overlapping. The larch or
tamarack with its shiny needled leaves resembles an ever- green but is
deciduous. Evergreen leaves are retained from two to five years.
Functions of Leaves
The most important function of all green tissue is that of food- making. Called
photosynthesis, this function is performed chiefly by the leaves, although it is
carried on by green tissues in whatever part of the plant they may be found.
Another function, common to both plants and animals, is respiration. This
involves the intake of oxygen and the discharge of carbon dioxide. The exchange
of gases is accomplished in leaves through millions of microscopic pores in the
leaf surface. The leaves are well fitted for their task by having a large surface
through which the respiratory gases may pass freely.
The large leaf area with its innumerable pores serves still another function, that
of releasing excess water from the plant in the form of water vapour, a process
called transpiration.
d) Flower
Let us imagine a stem bearing a whorl of leaves at each of the last four nodes at
its tip. Now let the internodes (the stem portions between nodes) become so
shortened that the four whorls are stacked very closely together. We are able
now to visualize a flower from a botanist's point of view. The lowest whorl
remains green and leaf-like; the next, somewhat larger, becomes brightly
coloured, and is composed of the well-known flower petals. The two together
make up the floral envelope.
Petal
Pistil
Stamen
Seeds
The remaining two whorls bear little resemblance to ordinary leaves. They have
been greatly modified to carry out the one and only function of a flower, the
production of seed, and are often referred to as the essential organs.
Part B: Life Cycle of a Plant
Seed Formation
Flowering plants produce seeds which are the outcome of a sexual process
called fertilization in which a male sperm (pollen grain) and a female egg unite.
The male sperm (pollen) are produced in the stamens of a flower and the female
eggs are produced at the base of the pistil of the flower. Eggs and pollen come
together in a plant by the process of pollination.
If the eggs of a plant are fertilized by the pollen of the same plant the process is
called self-pollination. Cross-pollination is defined as the transfer of pollen from
the stamens of one flower to the flower of another plant.
Sprouting of Seeds
Seeds can sprout or germinate soon after they are formed or may remain
dormant for considerable periods of time. In order for seeds to sprout, they
require the correct moisture, a suitable temperature, appropriate nutrients, and
sufficient oxygen.
Growing Plant
As the plant grows, the stem lengthens, number of leaves increase, and the
overall height increases. For many plants, the size and shape of the leaf and
colour of the flowers remain unchanged through the growth cycle.
First leaf
Leaf
Developing first leaf
Sprouting plant
Seed
Life Cycle of a Bean Plant