Unit 4: Plants


1. Energy:
Plants capture energy from incoming solar
radiation and convert it to chemical energy
through photosynthesis, a complex process that
uses carbon dioxide and water to form glucose
and oxygen. The word equation for
photosynthesis is:
solar energy


Carbon dioxide + water  glucose +
oxygen





Plants produce glucose which is a carbohydrate.
Chemical energy plants need for maintenance,
growth, and development.
Photosynthesis needs: CO2 + H2O+light
Plants have many adaptations to gain light For
example, some plants can adjust the position of
their leaves to maximize their exposure to
sunlight.
https://www.youtube.com/watch?v=EvXHfFvAZg


2. Protection against herbivores:
Plants get eaten.
 Good for us/animals = bad for plants

Since plants cannot move theydeveloped
other ways to protect themselves.
Ex: Many plants produce toxic or bad-tasting
substances to keep herbivore away. Others
produce a tough, hair, or prickly outer layer.



3. Nutrients:
Plants need nitrogen (N), phosphorous (P),
and potassium (K), in order to synthesis the
proteins, lipids, and other compounds
needed in their cells.
Plants absorb nutrients as dissolved
substances in water.

Most plants are helped in this process by
mycorrhizal fungi associated in their roots.

This fungi has a mutualistic relationship with
the plant, whereby the plant provides the
fungi with carbohydrates and in return, the
fungi provides the plant with the nutrients by
its ability to absorb water and minerals.



4. Water:
Plants need water for photosynthesis and
many other processes, such as growth and
repair of cells.
If a plant loses too much water it will wilt and
may die; similarly, it may die if it is exposed to
too much water.



5. Gas Exchange:
Plants are living organisms and need to
exchange gases with the environment during
processes such as photosynthesis and cellular
respiration.
In vascular plants, most gas exchange
happens in the leaves.


6. Reproduction:
Plants need to reproduce.

asexual and sexual reproduction – meaning that
male and female gametes, usually from two
individuals, have to meet and join.

Since individual plants cannot move, plants have
evolved some amazing adaptations to ensure
that their gametes unite and that the resulting
zygote has an appropriate environment in which
to germinate and grow.
Flowering plants are
divided into two main
'body systems' –
roots & shoots

The Root System:
 Includes all the root material
 Underground (usually)
 Anchor the plant in the soil
 Absorb water and nutrients
 Conduct water and nutrients
 Food storage





The Shoot System:
Includes the stems and leaves (and
reproductive parts)
Above ground (usually)
Elevates the plant above the soil
Many functions including:
 Photosynthesis
 Reproduction and dispersal
 Food and water conduction

Vascular plants have three main nonreproductive organs: the leaf, the stem and
the root. These organs are primarily
composed of three tissue types:
 dermal tissue
 vascular tissue
 ground tissue.
STRUCTURE:
 Two tissue types: epidermis and periderm
 Outermost cell layers
 Often have thicker cell walls
 Covered with a waxy cuticle
FUNCTION:
 Protect against injury, herbivores, disease
and water loss
Structure:
 Two tissue types: xylem and phloem
 Xylem: thick-walled cells, dead at maturity
 Phloem: thin-walled cells, living at maturity
Function:
 Transport water and nutrients
 Support the plant body
Structure:
Three tissue types:
 Parenchyma: thin-walled cells, living at
maturity
 Collenchymas: thick-walled cells, living at
maturity
 Sclerenchyma: cells with lignin in their cell
walls, dead at maturity

Perform cellular processes to support growth
and development (parenchyma and
collenchyma)

Store carbohydrate, especially starch
(parenchyma)

Support and protect plant body (collenchyma
and sclerenchyma)

Area of actively dividing undifferentiated
cells.

Eventually develop into specialized cells and
tissues.
Produce new cells through mitosis.


In plants, mature cells cannot divide. This
means that the plant can only grow where
there is meristematic tissue. (root tips, buds)

https://www.youtube.com/watch?v=h9oDTM
XM7M8

There are three major groups of vascular
plants
 Lycophytes and pteridophytes
 Gymnosperms
 Angiosperms

https://www.youtube.com/watch?v=gTQ9gs
ZBMPI

Angiosperms have traditionally been divided
into monocots or dicots based on whether
the seeds of angiosperms have one or two
cotyledons.

Cotyledons are a structure in the seeds of
flowering plants (angiosperm) that stores and
supplies nutrients to the embryo.

https://www.youtube.com/watch?v=gI2RxzA
T-ww