01. Plants
The Organisms that produce their own food or the nutrients by themselves are known as
autotrophic organisms. Autotropism can be divided into two categories according to the
type of energy they use for food production. If solar energy is used, they are known as
photoautotrophic and if energy is obtained by a chemical reaction within the plants
themselves, they are known as chemoautotrophic. Most of the plants are photoautotrophic.
Most bacteria are chemoautotrophic. Production of food inside the chloroplast of plant cells
using chlorophyll, which is a specific organic compound, is called photosynthesis.
Energy Transfer Diagram for Photosynthesis can be written as follows.
Light Energy
Stored Chemical Energy (Starch)
Chlorophyll
/ Leaf
Glucose, which is a by product of photosynthesis, belongs to a macro-molecule/nutrient,
carbohydrate, and also a simple sugar/monosaccharide. Plants do produce excess
amounts of glucose than needed immediately. As glucose is a simple sugar, it would be
soluble in water, which can not be easily stored within the plant cells, therefore these
glucose molecules get together to form a polysaccharide/complexed molecule called
starch which doesn’t dissolve in water and can be stored for later uses. This starch which is
been produced will be stored in the chloroplasts.
Parts
Cell Wall
Cell
Membrane/Plasma
Membrane/ Semi1|P ag e
Functions
Dead structure. Main constituent of cell wall is cellulose. It maintains
the shape of the cell and supports and protects the cell.
Controls the entry and exit of material in and out of the cell. Only
permits the entry of water molecules, ions and some other
molecules.
permeable
Membrane
Cytoplasm
Nucleus
Mitochondrion
Golgi Complex
Ribosome
Endoplasmic
Reticulum
Vacuole
Chloroplast
Gelatinous liquid which maintains the shape of the cell, bears cell
organelles and carries out all the metabolic processes.
The control center of the cell. Stores and transfers genetic material
from one generation to another.
Also called the power house. Aerobic respiratory reactions take
place within to release energy for the survival of the cell.
Produces secretory substances, packaging and secretion.
Synthesizes Proteins.
Also called transport system, helps to move substances around the
cell.
The fluid filled, large space found within the cell. Functions to
maintain water balance, supports and provides color to the cell by
the pigments found within.
Has the green pigment chlorophyll within. Converts light energy
obtained from the sun to chemical energy.
Step
No.
Method/Procedure
Reasoning
A
Dipping the leaf in
boiling water for about
2 minutes
B
Boil the leaf placed in a
test tube containing
ethanol. (double boil)
Dip the leaf again in hot
water
Place the leaf on a tile
and add iodine
Kills the leaf cells, disrupts the cell
membrane, kills/removes the waxy
cuticle, so that extraction of
chlorophyll and penetration of iodine
will be done easily.
Only alcohol can extract chlorophyll
from the leaf cell.
*
C
Further softens the leaf.
The leaf turns blue black if starch
present.
Fertilizers – Are mineral salts that are naturally as well as artificially available in the soil which
can be replaced, but not any time sooner. Artificial fertilizers are used to replace the mineral salts
that are been absorbed by the plants. Mineral salts are important for the plant tp grow stronger
and larger.
1. Nitrate – Required for protein synthesis within plant cell as protein is needed for the
making of new cells, as it is important for the growth of a plant. Also required for
chlorophyll synthesis, deficiency of this salt would lead to yellow leaves.
2. Magnesium – Required for the synthesis of chlorophyll.
Investigate or research the importance of the mineral salts – Phosphorous, Potassium, Iron,
Calcium, Zinc, Sulphur with their role on plant growth and their deficiency symptoms.
Too much of fertilizers can cause the following.
-Your plants can get what is called burn or fertilizer burn, which causes them to look dried out
and unhealthy. What is happening here is not that the fertilizer is taking any nutrients from the
soil, but the large amount of fertilizer in the soil is making if very hard for the plant to absorb
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water. If this does happen, you can try giving your plants extra water to wash out the excess
fertilizer.
-If you use too much fertilizer you can change the pH of your soil, which means that you are
changing the plants environment from one they like to grow in to one they might not like to grow
in. Farmers often test the pH (environment) of their soil to make sure the plants can stay healthy in
that environment.
-Adding too much of one nutrient can make it difficult for plants to absorb other nutrients. Plants
need man different kinds of nutrients, such as nitrogen, phosphorus, potassium, calcium, iron,
and more. You may have learned about these nutrients in science class or recognize them as
things that even humans need! Well just like you have to have a balanced diet, so do plants. For
example, giving a plant too much nitrogen means it might not be able to get enough potassium.
So balance is very important.
-It should be noted that adding too much fertilizer can be bad for the environment. If you add too
many nutrients that the plants cannot use, the extra can be washed away into rivers and oceans
which may not be good. This isn’t so much a concern for most people with a few plants, but it is
something that large farms need to think about.
Activity 1.3 – Construct an investigation for the activity and try answering it on your own.
Plants and Water –
1. Water for support - Plants also contain more water than
animals, plants are about 90% water. The amount of water a
plant needs depends on the type of plant, how much light the
plant gets, and how old the plant is. When plants are not
watered properly, they wilt. This is because of something
called turgor, which is water pressure inside the cells that
make up the plant's skeleton. Water enters a plant through
its stem and travels up to its leaves. When a plant is properly
hydrated, there is enough water pressure to make the leaves
strong and sturdy; when a plant doesn't get enough water,
the pressure inside the stems and leaves drops and they wilt. The vacuole contains water
which would make all the cells filled with water and press against each other to maintain
the structure of the plant.
2. Water for transport – Water allows the transportation of mineral salts that are absorbed by
the roots, as mineral salts are dissolvable in water. Transportation of water along with
mineral salts will be through xylem vessels.
3. Water for cooling - Plants need to cool themselves for several reasons. When
temperatures are too high, energy systems (metabolic functions) slow, and growth and
flowering slows or stops. In extreme heat, plants are severely stressed and can die.
Sometimes heat will cause bubbles to form that block the flow of water, leading to
dehydration. Transpiration is an evaporative cooling system that brings down the
temperature of plants, but since it leads to water loss, it must be accurately regulated. The
ingenious system that regulates this function consists of a guard cell on each side of the tiny
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pores (stomata). When water moves into the guard cells, they swell and arch open; as
water moves out, the guard cells relax and close. The guard cells are sensitive to light
intensity, temperature, wind, relative humidity and carbon dioxide concentrations inside
the leaf.
4. Water for photosynthesis – Plants with enough water and carbon dioxide harness the
power of photons gathered from sunlight to complete photosynthesis. The six molecules of
carbon dioxide and six molecules of water on the left side of the photosynthesis equation
break apart and reconfigure into glucose and six molecules of oxygen. The sugar (glucose)
can be used for energy immediately or stored for later use while the oxygen releases
through the plant’s pores as a waste product.
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