<p>UNIT 3: PLANTS<br />
CROPS<br />
Crops are useful plants grown by farmers in the farm.<br />
Types of Crops<br />
-There are two types of crops<br />
(a) Food crops<br />
(b)Cash crops<br />
a) FOOD CROPS<br />
Grown mainly for food<br />
Examples of food crops<br />
a) Cereal<br />
• Maize<br />
• Rice<br />
• Wheat<br />
• Barley<br />
• Sorghum<br />
• Millet<br />
b) Legumes<br />
• Beans<br />
• Peas<br />
• Black beans<br />
• Green grams<br />
• Groundnuts<br />
• Cow peas<br />
• Soya beans<br />
c) Vegetables<br />
• Kales<br />
• Cabbage<br />
• Spinach</p>
<p>____<br />
____<br />
d) Fruits<br />
• Pawpaws<br />
• Oranges<br />
• Lemons<br />
• Pineapples<br />
• Mangoes<br />
• Tangerines<br />
e) Tuber crops<br />
• Sweet potato<br />
• Cassava<br />
• Yams<br />
• Irish potatoes<br />
• Arrow roots<br />
• Carrots</p>
<p>CASH CROPS</p>
<p>Grown for sale to get money.<br />
They are processed in factories into new products.<br />
Examples of cash crops<br />
a) Beverage crops – for making drinks e.g. Tea, Coffee, Cocoa<br />
b) Fibre crops – produce threads woven to make ropes, baskets, cloths,<br />
sacks, mats, etc. e.g. Sisal, Cotton, Palm tree<br />
c) Oil crops – produce oil e.g. Sunflower, Coconut<br />
Oil Crops<br />
-Plants that produce cooking oil<br />
-These crops include:<br />
(a) Coconut tree<br />
(b) Sunflower plants<br />
(c) Groundnuts<br />
(d) Macadamia</p>
<p>____<br />
WEEDS<br />
These are plants that grow where they are not wanted<br />
Examples of weeds<br />
Blackjack- has hooks that stick on clothes or fur<br />
Sodom apple- flowers are purple and white in colour.<br />
Fruits are yellow with short sharp thorns in the stem and leaves.<br />
Pigweed- used as a vegetable<br />
Wandering Jew<br />
Mexican marigold – yellow flower, Unpleasant smell<br />
Oxalis<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Control of Weeds<br />
The removal of weeds from a farm is called weeding.<br />
The removal of the unwanted parts in a plant is called pruning.<br />
Ways/Methods of controlling weeds<br />
a) Digging them out – is the best method<br />
b) Slashing<br />
c) Mulching<br />
d) Uprooting<br />
e) Using chemicals (herbicides)<br />
Effects of Weeds on Crops<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Weeds are harmful to crops in the following ways:<br />
Compete with crops for:<br />
• nutrients in the soil<br />
• carbon dioxide for photosynthesis<br />
• sunlight for photosynthesis<br />
• moisture content in the soil<br />
b) Weeds harbour diseases and pests that damage the crops.<br />
PLANTS<br />
Plants are living things.<br />
The grouping of plants together with common characteristics or features is<br />
called the classification of plants.<br />
Plants can be grouped into:<br />
a) Green and non-green plants<br />
b) Flowering and non-flowering plants.<br />
1 a) Green Plants<br />
They contain the green colouring matter called chlorophyll.<br />
They make their own food through a process called photosynthesis. e.g.<br />
Algae – grow in water bodies<br />
Moss – grow in damp places e.g. walls, cliffs, stones, etc.<br />
Conifers e.g pine, cedar, cypress.<br />
b) Non-green Plants<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
They do not contain green matter (chlorophyll)<br />
They do not make their own food &#8211; They feed on organic matter (dead<br />
decayed matter)<br />
Non-green plants comprise of fungi and bacteria<br />
Page 7 of 39<br />
Teachers Arena<br />
____<br />
____<br />
.Examples of fungi<br />
&#8211; Bracket tree<br />
&#8211; Penicillium<br />
&#8211; Puffballs<br />
&#8211; Mushrooms<br />
&#8211; Moulds<br />
&#8211; Toadstools<br />
&#8211; Lichen<br />
&#8211; Ringworms<br />
&#8211; Athlete’s foot<br />
&#8211; Dandruffs<br />
&#8211; Yeast<br />
&#8211; Mucor<br />
Penicillium – used to make medicine.<br />
Yeast – used for baking.<br />
2 a) Flowering Plants<br />
They produce flowers.<br />
Flowers bear fruits that contain seeds.<br />
They are green in colour and make their own food.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
b) Non-flowering Plants<br />
They do not produce flowers.<br />
They are both green and non-green.<br />
All non-green plants are non-flowering (fungi and bacteria)<br />
They reproduce by means of spores and cones which germinate into new<br />
plants.<br />
Plants that produce by means of cones (hard seeds) are called coniferous<br />
plants e.g. pine, cedar, cypress.<br />
Examples of non-flowering plants / how they reproduce<br />
Ferns &#8211; spores<br />
Algae &#8211; Spores<br />
Mosses &#8211; Spores<br />
Fungi &#8211; Spores e.g. mushrooms, mucor, puffballs etc.<br />
Coniferous plants &#8211; cones e.g. pine, cedar, cypress<br />
EXTERNAL PARTS OF A PLANT<br />
Parts of the plant are:<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
FUNCTIONS OF THE PARTS<br />
Roots<br />
a) Support/hold/anchor the plant firmly in the soil<br />
b) Absorption of water and mineral salts<br />
c) Food storage<br />
Points to Note:<br />
Plants that store food in the roots are called root tubers.<br />
Examples of plants that store food in the roots:<br />
• Arrow roots<br />
• Cassava<br />
• Carrots<br />
• Sweet potatoes<br />
There are two main types of roots:<br />
a) Tap root &#8211; extension of stem with side roots.<br />
b) Fibrous roots-many similar roots.<br />
i) Plants with tap roots include:-<br />
Legumes,<br />
Acacia,<br />
Fruit trees, etc.<br />
ii) Plants with fibrous roots include:-<br />
Cereals,<br />
Oats,<br />
Grass,<br />
Sisal,<br />
Onions,<br />
Sugarcane,<br />
Coconuts, etc.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Other types of roots include:<br />
a) Aerial roots – for breathing<br />
b) Prop roots – used in maize for support<br />
Stem<br />
&#8211; Transports water and mineral salts from the roots to the leaves<br />
&#8211; Carries food made by the leaves to the roots for storage<br />
&#8211; Holds or supports the upper parts of the plant in good position<br />
&#8211; Protects the plant<br />
&#8211; Some stems store food and water for the plant<br />
N.B. Plants that store food in the stem are called stem tubers.<br />
Examples of plants that store food in the stem are:<br />
a) Cactus<br />
b) Sugar cane<br />
c) Irish potato<br />
Leaves<br />
a) Breathing – Exchange of gases through small tiny holes called stomata.<br />
b) Photosynthesis – Process of making its own food<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Requirements of photosynthesis are:-<br />
Chlorophyll – green colouring matter<br />
Water<br />
Carbon dioxide<br />
Sunlight<br />
c) Storage of food – Edible vegetables<br />
d) Transpiration – Process in which plants lose excess water through small<br />
holes called stomata.<br />
Transpiration is high when it is hot, sunny, dry, windy.<br />
It is low when it’s cold, wet, calm and rainy.<br />
Flower<br />
– Reproductive organ of a plant<br />
It bears fruits which contains seeds that germinate into a new plant<br />
Seeds germinate into new young plants called seedlings<br />
What is a flower?<br />
A flower is a reproductive part of a flowering plant.<br />
Most plants have both male and female reproductive parts.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Functions of the Parts<br />
Flower stalk: It joins the flower to the plant i.e. on the stem or a branch.<br />
It holds and supports the flower.<br />
Sepals: They are green in colour. Sepals protect the inner parts of<br />
the flower while it is growing in the bud.<br />
A collection of sepals is called calyx. Sepals can assist in photosynthesis.<br />
Petals: These are the outermost parts of the flower. They are<br />
usually brightly coloured to attract insects and some birds that help in<br />
pollination<br />
A collection of petals is called a corolla.<br />
Filament: It is a stalk that holds/supports the anthers.<br />
Anther: It produces pollens<br />
The pollen contains pollen grains which are the male sex cells of a flower.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Stigma: It receives pollen grains during pollination from the anthers.<br />
Style: It is a long and narrow tube that joins the stigma and the<br />
ovary.<br />
Ovary: It contains and encloses the ovules.<br />
The ovary develops into a fruit after fertilization.<br />
Ovules: Ovules are the female sex cells of a flower.<br />
Ovules develop into seeds that germinate into new plants after fertilization.<br />
Receptacle: It connects the flower stalk and the ‘ovary base’.<br />
Stamen: The male part of a flower is the stamen. The stamen consists of<br />
:-<br />
&#8211; Anthers<br />
&#8211; Filament<br />
In a pawpaw plant, male and female reproductive parts are on separate<br />
plants.<br />
Pistil: The female part of a flower is the pistil. A group of pistils are called a<br />
carpel. The pistil comprises:<br />
• Ovary<br />
• Stigma<br />
• Ovules<br />
• Style<br />
Ovules are the female reproductive cells of a flower.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
The pistil consists of:-<br />
The Nectary is at the base of the sepals. It produces sugary substances<br />
called nectar which is food for insects such as bees and butterflies.<br />
In the maize plant the female and the male reproductive parts are in<br />
different positions on the same plant.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
POLLINATION<br />
What is pollination?<br />
It is the transfer of pollen grains from the anthers to the stigma.<br />
TYPES OF POLLINATION<br />
There are two types:<br />
a) Self pollination<br />
b) Cross pollination<br />
What does the pollen grain contain?<br />
&#8211; The male reproductive cells of a plant<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
a) Self pollination<br />
What is self pollination?<br />
It is the transfer of pollen grains from the anther within the same flower or<br />
to the stigma of the same flower or of another flower on the same plant.<br />
b) Cross pollination<br />
What is cross pollination? |<br />
It is the transfer of pollen grains from the anther to the stigma from one<br />
plant to another.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
AGENTS OF POLINATION<br />
What are agents of pollination?<br />
These are the things that help transfer pollen grain from the anther to the<br />
stigma.<br />
Agents of pollination are:<br />
a). Insects &#8211; bees -butterfly<br />
b). Wind<br />
c). Birds -sun bird -humming bird -honey bird<br />
d). Water<br />
N.B. Birds and insects visit flowers to collect nectar. They are attracted by<br />
coloured petals and the sweet smell of the petals (scent). They carry the pollen<br />
grains from one flower to another.<br />
Characteristics of wind-pollinated flowers<br />
Wind-pollinated flowers:<br />
• Are small in size.<br />
• Have dull petals i.e. not brightly coloured.<br />
• Have no scent (no sweet smell)<br />
• Have no nectar.<br />
• Have large anthers which are loosely attached to the<br />
filament. This makes them shed the pollen grains when<br />
the air moves slightly around.<br />
• Produce a large amount of light and powdery pollen<br />
grains which can be easily carried by the wind.<br />
N.B. Large amounts of pollen grains are produced because a lot of them are<br />
lost on the way to the next plant.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
• Have large hairy or feathery stigmas. The stigmas hang<br />
outside the flower and trap any pollen grains that may<br />
be floating in the air.<br />
N.B. An example of a wind-pollinated flower is the maize flower.<br />
Characteristics of insect-pollinated flowers<br />
Insect pollinated flowers;<br />
• Have flat and sticky stigmas that are found inside the<br />
flowers to stick pollen grains deposited by an insect.<br />
• Produce a small amount of heavy and sticky pollen<br />
grains which can stick firmly to the bodies of visiting<br />
insects.<br />
• Have anthers which are not very large.<br />
• Produce nectar which acts as food for the insects.<br />
• Have a strong, sweet smell called scent that attracts the<br />
insects.<br />
• Have brightly coloured petals that attract the insects.<br />
• Are usually large in size.<br />
N.B. An example of an insect-pollinated flower is the sunflower<br />
FERTILIZATION IN PLANTS<br />
Fertilization is the fusion of the male cell in the pollen grain and the female<br />
cell in the ovary to form a seed.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Fusion is the joining of the two cells.<br />
When pollen grain falls in the stigma, it germinates to form a pollen tube.<br />
The pollen tube grows/develops down the style to the ovary.<br />
The pollen tube carries the male reproductive cells (gametes) to the ovary.<br />
In the ovary, the pollen grain fuses (joins) with ovules (female reproductive<br />
cells). Fertilization is then said to have taken place.<br />
After fertilization:<br />
a) Ovules become seeds.<br />
b) The ovary develops into a fruit.<br />
c) The other parts of the flower wither and fall off.<br />
Stages that lead to fertilization<br />
What is found when pollen grains germinate?<br />
A pollen tube is formed.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Where does the pollen tube grow?<br />
In the stigma and through the style<br />
What is carried along the tube?<br />
Pollen grains<br />
After fertilization what forms the seed?<br />
The ovules<br />
What does the ovary develop into?<br />
The fruit<br />
PARTS OF A SEED<br />
There are two types of seeds:<br />
a) Monocot seed<br />
b) Dicot seed<br />
PARTS OF A MONOCOT SEED<br />
An example of a monocot seed is Maize.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Testa/Seed coat: It is the outermost skin of a seed that protects the<br />
inner parts of the seed.<br />
Embryo: This is the part which can grow into a new plant. It has two<br />
parts:<br />
a) Radicle – Develops into a root<br />
b) Plumule – Embryo part that grows into a shoot (leafy part)<br />
Endosperm: Stores food for the seed.<br />
Fruit scar: Point where the maize grain was attached to the cob (ovary)<br />
Style scar: Marks the point that was attached to the style (remains of the<br />
style)<br />
N.B. A maize seed has two scars.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
PARTS OF A DICOT SEED<br />
An example of a dicot seed is a bean seed.<br />
Testa: For protection of inner parts.<br />
Radicle: Grows into a root<br />
Plumule: Grows into a shoot<br />
Microphyle: It is a tiny hole that allows air and water to enter into the<br />
seed during germination.<br />
Scar/Hilumo: Is the part at which the seed was attached to the ovary.<br />
Cotyledon: Stores food that is used during germination.<br />
Cotyledon is also called seed leaf.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Illustrations of Fruits and seeds showing the scars<br />
N.B. Flowering plants with one cotyledon are called monocotyledons<br />
e..g maize, wheat, rice, millet, sorghum etc.<br />
Flowering plants with two cotyledons are called Dicotyledons<br />
e.g. beans, peas, soya beans, green grams, etc.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Differences<br />
GERMINATION<br />
Germination is the process in which a seed develops into a young plant.<br />
A young plant is called a seedling.<br />
STEPS OF SEED GERMINATION<br />
1. The seed absorbs water and oxygen 9air) through the<br />
tiny hole called microphylle.<br />
2. The water makes the seed swell up.<br />
3. The seed coat bursts and splits open.<br />
4. The radical comes out through the microphylle to form a<br />
tiny roof that grows into the soil.<br />
5. Shortly after,the plumule forms with tiny leaves.<br />
6. A new plant is formed (seedling)<br />
N.B. During the initial stages of germination the seed used the food<br />
stored in the cotyledon or endosperm before leaves develop to carry<br />
out photosynthesis.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Conditions necessary for germination<br />
• Water/moisture<br />
• Air (oxygen)<br />
• Warmth<br />
What is the difference between a fruit and a seed?<br />
&#8211; Fruit have two scars while seeds have only one scar.<br />
The new plant is the seedling. During germination, the growing embryo<br />
feeds from the cotyledon.<br />
After germination, cotyledons turn green and start making food before<br />
the tiny leaves develop.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Experiments<br />
Activity 1<br />
What is necessary for germination?<br />
&#8211; Air;<br />
&#8211; Water;<br />
&#8211; Warmth.<br />
Seeds will germinate since oxygen, water and warmth is available.<br />
Activity 2<br />
What is present?<br />
&#8211; Air<br />
&#8211; Warmth.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Dry cotton wool indicates water/moisture is lacking, hence seeds will not<br />
germinate.<br />
Activity 3<br />
What is present?<br />
-Water,<br />
&#8211; Warmth.<br />
Water is boiled and then cooled to remove the oxygen.<br />
The layer of oil prevents the oxygen from dissolving into the water.<br />
Seeds will NOT germinate since there is no oxygen.<br />
Activity 4<br />
Place the set up in a freezer or refrigerator.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Ice cubes make the temperatures very low, hence there is no warmth.<br />
Seeds will not germinate because there is no warmth.<br />
INTERDEPENDENCE IN PLANTS<br />
Interdependence is a situation whereby living things depend on each<br />
other.<br />
All living things depend upon each other in many ways.<br />
TYPES OF INTERDEPENDENCE<br />
i) Interdependence between plants<br />
ii) Interdependence between plants and animals<br />
iii) Interdependence between animals.<br />
1. Interdependence between plants and other plants<br />
i) Shade<br />
ii) Support<br />
iii) Habitat<br />
Shade<br />
1. Plants that cannot grow in direct sunlight grow under bigger plants such<br />
as trees.<br />
2. An example of a plant that grows under a shade is the fern plant.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Support<br />
1. Plants with weak and soft stems which cannot stand firmly by<br />
themselves depend on other plants for support. They are called climbing<br />
plants.<br />
2. They have special features to climb on other plants e.g.the passion<br />
plant has tendrils to climb on other plants while the bougainvillea has<br />
hooks to climb.<br />
3. Others like the garden pea twine around other plants.<br />
Habitat<br />
1. A habitat is the natural place where a plant grows or an animal lives.<br />
2. Some plants grow on other plants e.g. lichen.<br />
3. Others live and feed directly from the host. They are called parasitic<br />
plants e.g. dodder plant<br />
Others feed on dead and decaying plants. They are known as saprophytes<br />
e.g. mushroom and toadstool.<br />
2. Interdependence between plants and animals<br />
Plants and animals depend on each other in the following ways:<br />
1. For oxygen<br />
2. For carbon dioxide<br />
3. For food<br />
4. For medicine<br />
5. For pollination<br />
6. For shelter<br />
7. For nutrients<br />
8. Animal wastes<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
9. Decomposition on death<br />
Food<br />
1. Herbivorous animals feed on plants directly. Carnivores feed<br />
on them.<br />
2. Animals produce carbon dioxide which is used by plants<br />
during photosynthesis to make food.<br />
Oxygen<br />
1. During photosynthesis, plants produce oxygen which is used<br />
by animals during respiration.<br />
Carbon dioxide<br />
1. During respiration, animals give out carbon dioxide which is<br />
used by plants to make their own food.<br />
Medicines<br />
1. Many plants are a source of medicine e.g. Aloe vera,<br />
Mwarubaini (neem tree), ginger, garlic.<br />
2. Penicillin and quinine are modern medicines extracted from<br />
plants.<br />
Pollination<br />
1. Most plants depend on animals such as bees, butterflies and<br />
birds like the sunbird for pollination.<br />
2. Pollination allows reproduction in plants.<br />
Animal waste<br />
1. Animal droppings and dung add nutrients to the soil.<br />
2. The nutrients are absorbed by the plants through the roots.<br />
Shelter<br />
1. Some animals depend on trees for shelter and protection from<br />
rain, wind, heat and cold.<br />
2. Birds build nests on trees, monkeys live on trees and termites<br />
build their shelters on trees.<br />
Nutrients<br />
1. Animals get nutrients by eating. Insectivorous plants trap<br />
insects and feed on them.<br />
2. Plants get nutrients from dead and decaying animal waste.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Decomposition<br />
1. Living things die, decay and rot. The process of rotting and<br />
decaying is known as decomposition.<br />
2. After decomposition, nutrients are released to the soil and<br />
then used by plants.<br />
FOOD CHAIN<br />
1. A food chain is a feeding relationship among living things.<br />
2. The producers in a food chain are plants.<br />
3. Herbivorous animals feed on plants and are called primary<br />
consumers.<br />
4. Carnivorous animals feed on herbivores and are called<br />
secondary consumers.<br />
5. Animals that feed on secondary consumers are called tertiary<br />
consumers.<br />
6. Finally, in a food chain we have decomposers who bring about<br />
decomposition.<br />
Living things in a food chain<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Examples of food chains<br />
CROP PESTS<br />
1. A pest is a harmful thing, person or animal.<br />
2. Pests are grouped into two: &#8211; Field pests<br />
&#8211; Storage pests<br />
FIELD PESTS<br />
They attack crops when they are in the field.<br />
They include: &#8211; Weaver birds<br />
&#8211; Army worms<br />
-Cut worms<br />
-Stalk borers<br />
&#8211; Aphids<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
&#8211; Locusts<br />
STORAGE PESTS<br />
They attack and destroy stored crop produce. They include:<br />
• Rodents like rats, mice and squirrels<br />
• Weevils<br />
• White ants (termites)<br />
Weevils<br />
They bore holes in grains and eat them reducing their quality.<br />
Rodents<br />
They attack and destroy grains.<br />
White ants<br />
They eat stored grains and root tubers e.g. yams.<br />
Crop pest Crops attacked Part attacked<br />
1. Locust All growing crops Leaves<br />
2. Aphids Beans, cabbage,<br />
groundnuts. peas, sorghum,<br />
carrot, tobacco<br />
Stem and leaves<br />
3. Army worms Cereals, cassava, grass Leaves<br />
4. Stalk borer Sugarcane, maize, rice,<br />
sorghum, millet<br />
Stem<br />
5. Cut worms Cabbages, tomatoes,<br />
potatoes, maize, wheat, rice<br />
Stems of young plants<br />
6. Weaver birds Rice, maize, wheat, millet,<br />
sorghum<br />
Eat the grains<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
EFFECTS OF CROP PESTS ON CROPS<br />
1. Lower yields: The quantity of the harvest is reduced.<br />
2. Reduced quality of produce: The produce is not attractive to the<br />
buyer. This leads to a loss for the farmer.<br />
3. Transmission of diseases to crops: Some plants transmit diseases to<br />
crops e.g. aphids.<br />
4. Transmission to consumers: Crops attacked by pests may cause<br />
diseases to consumers<br />
CONTROL MEASURES FOR CROP PESTS<br />
Pests are reduced or eliminated by the following methods:<br />
1. Scaring<br />
2. Trapping<br />
3. Hand-picking<br />
4. Weeding<br />
5. Spraying<br />
6. Pruning<br />
7. Biological method<br />
Scaring: Birds and monkeys can be kept away by scaring, using<br />
scarecrows or metals that make unpleasant noise.<br />
Trapping: Traps are put where pests are commonly found.<br />
Hand picking: Some pests can be hand-picked. Hand-picking is best<br />
used in small pieces of land.<br />
Weeding: This is the removal of unwanted plants. Some weeds host<br />
pests.<br />
Spraying: Pesticides are sprayed on crops to control pests.<br />
Pruning: Remove the affected parts of a plant and destroy them.<br />
Biological method: This is the use of other animals to feed on pests<br />
e.g. Ladybirds feed on aphids which affect crops.<br />
ADAPTATION OF PLANTS TO THEIR ENVIRONMENT<br />
Adaptation is the ability/or a mechanism of a plant to survive in a particular<br />
environment or habitat.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
PLANTS ADAPTED TO DIFFERENT ENVIRONMENTS<br />
Xerophytes &#8211; Plants that grow and survive in dry areas.<br />
Mesophytes &#8211; Plants that grow and survive under normal<br />
conditions<br />
Hydrophytes -Plants that grow and survive in watery areas.<br />
Halophytes &#8211; Plants that grow in salty areas.<br />
Adaptation of plants to survive in dry areas (Desert – Arid and Semi-<br />
Arid)<br />
• These plants suffer water shortage<br />
• They are called Xerophytes<br />
• They conserve water either by their structure or through their<br />
behaviour.<br />
• Examples include:<br />
• Cactus<br />
• Acacia<br />
• Euphorbia<br />
• Baobab tree<br />
• Sisal<br />
• Marram grass<br />
• Prickly pear<br />
• Blue gum tree<br />
Cactus plant in desert<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
Adaptation of Xerophytes<br />
1.Some plants shed their leaves during dry season to reduce the rate of<br />
transpiration. Plants that shed (lose) their leaves are called deciduous<br />
plants.<br />
They do not carry out photosynthesis during dry season hence they<br />
become dormant i.e. inactive.<br />
2. They have needle-like leaves. The surface area of the leaves is small,<br />
hence it reduces the rate of transpiration.<br />
3.They have sharp spines. This protects the plant from being eaten by<br />
desert animals and also reduces water loss.<br />
4.Some plants roll/fold or curl their leaves. This reduces the rate of<br />
transpiration. They also trap moist air and make it available for the plant.<br />
5. Some have normal or silvery (shiny) hairs. Normal hairs trap water<br />
vapour for the plant. Shiny hair reflects sunlight and heat the leaves, hence<br />
reduce<br />
temperatures on the plant’s surface.This reduces the rate of<br />
evapotranspiration.<br />
6. Other plants have leaves covered by a thick waxy cuticle. The wax<br />
reduces the amount of water loss through evaporation.<br />
7.Some plants have fleshy, thick green stems instead of leaves for<br />
photosynthesis. The thick stem does not allow much water to be lost e.g.<br />
cacti plant.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
8.Others have fleshy stems that store large amounts of water in their<br />
tissues. Plants with fleshy stems are called succulents.<br />
9.Some close the stomata during the day when the rate of evaporation is<br />
high and open during the night.<br />
10. Some have fewer or sunken stomata to reduce water loss.<br />
11. Some are deep-rooted to obtain underground water e.g. acacia.<br />
Adaptation of plants to survive in water (wet areas)<br />
These plants are called Hydrophytes<br />
They face a big problem obtaining energy oxygen<br />
Examples of hydrophytes are water lily, buttercup, water lettuce,<br />
duckweed, aquatic ferns.<br />
Water lily<br />
Adaptation of Hydrophytes<br />
1. They have thin cuticles since they do not have to reduce the<br />
amount of water loss.<br />
2. They have an increased number of stomata.<br />
Most of the stomata are on the upper surface of the leaf and<br />
remain open most of the time to allow absorption of gases<br />
from air.<br />
3. They have flexible stems that sway or bend with the currents<br />
so that they are not broken.<br />
4. They have large flat leaves to enable the plant float on water<br />
e.g. water lily.<br />
EDUCATIONNEWSHUB.CO.KE<br />
____<br />
____<br />
5. The leaves have air sacs that enable the plant to float in water.<br />
6. Some have hairs on the stems and leaves to prevent water<br />
from standing and soaking into the plant.<br />
7. Some have a waxy layer on the stem and leaves to prevent<br />
water from entering into the plant.<br />
8. Their roots are shallow and small to reduce the amount of<br />
water absorption.<br />
9. They have floating flowers above the water to facilitate<br />
pollination.<br />
NB: Mesophytes grow under normal soils and water conditions.<br />
They require an average amount of water e.g. beans, maize, bananas,<br />
potatoes.<br />
SIGNS OF UNHEALTHY CROPS (ILL-HEALTH)<br />
a) Stunted growth – also known as retarded growth. Plants develop at<br />
a slower rate than expected.<br />
b) Discolouration of plant parts. Other than the normal colour of the<br />
parts,they gain a different colour e.g leaves turn yellow ,hence the<br />
photosynthesis process is affected.<br />
c) Curled/folded leaves.<br />
d) Wilting. Plants may wither and die i.e. appear weak.<br />
e) Presence of spots, streaks, dots or patches. (Streaks are thin lines)<br />
f) Distortion or malformation – Abnormal shapes<br />
EFFECTS OF CROP DISEASES<br />
• Reduced yields – The quantity of harvest is less than<br />
expected.<br />
• Reduced quality of the produce i.e. the produce is not up to<br />
the expected standards e.g. small maize grains, fruits or kales.<br />
• Leads to high production cost. More expenses are incurred<br />
when controlling the diseases.<br />
EDUCATIONNEWSHUB.CO.KE</p>

