Plants 3rd grade

Lesson 1: What are the main parts of a plant?

Why Plants need leaves?
A plant’s leaves make up its leaf system. A system consists of parts that
work together. The main job of a leaf is to make food for a plant. Leaves do
this by using sunlight for energy to take apart water from the ground and
carbon dioxide from the air. Leaves use parts of water and carbon dioxide to
make sugar. This food making is called photosynthesis, a large word which
means making something new (synthesis) using light (photo).

Other ways Leaves help Plants…
Water gets to the leaf through a set of pipes inside the tree which goes all the way
down to the roots. Roots take water in from the soil so that it can be used by the tree.
There are also chemicals in the water which help the plant stay healthy, a lot like
vitamins help people stay healthy. In winter, the ground freezes. This makes it hard for
water to get into the soil. Roots can't get as much water from the soil in winter as in
the warm seasons of the year.

A plant´s leaves may also help to protect the plant
from being eaten. Leaves might be poisonous, sharp,
tough to chew. hungry animals will leave the plant
alone.
Photo: Stinging needle (Urtica dioica)

Lesson 2: Why do plant need roots and stems?

TYPES OF ROOTS
-The root system is often below the ground where you cannot see it.
-The roots hold the plant in the ground.
-Roots take in water and materials from the soil.
-Roots also store food made by the plant.

Parts of roots
Primary root: originates at
germination stage at the
radicle of the seed.
Secondary root: arise from
The primary root.
Root cap: indicates growth of new cells.
Root hair: tiny one celled hair-like
extension that increases the plant´s
ability to absorb water and minerals
from the soil.

Stems
A plant’s stems hold up its leaves, flowers, and fruits. Most plants have
tubes that move water and minerals from the roots of the plants to the
stems and roots.
Example: notice how thick cactus stems can be. Cactus stems swell up as they store
water. The stem shrink as the plant uses water. Cactus stems also have a thick, waxy
covering to help keep them from losing water. This type of stem helps the cactus
survive in a desert. Also some stems have thorns, spines and stinging hairs to keep
hungry animals from eating them.

When you eat a potato, you eat a stem part that stored food underground.
Undergroung stems can sprout new stems from buds such as the potato’s
«eyes». These parts grow upward and become new plants

Plants 3rd grade

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