learning objective - nbiinbii.polytechnic.edu.na/nust.na/web/sites/default/files/documents... ·...
TRANSCRIPT
Learning objective
• Plant structure of the main parts of a typical flowering plant
• Describe the function of roots and stem • Label the parts of a flower on a
diagram, and describe the functions of each part
• What is the difference between pollination and fertilization?
Plant Body Organization A plant consists of: 1. Root system, which is underground -Anchors the plant, is used to absorb water
and minerals, conduction and storage 2. Shoot system, which is above ground -Consists of supporting stems,
photosynthetic leaves and reproductive flowers
Each has an apex that extends growth
Both systems depend on the other.
– Lacking chloroplasts and living in the dark,
roots would starve without the sugar and other organic nutrients imported from the photosynthetic tissues of the shoot system.
– Conversely, the shoot system (and its reproductive tissues, flowers) depends on water and minerals absorbed from the soil by the roots.
MAIN ROOT
LATERAL OR SIDE
ROOT ROOT
SYSTEM
LEAF STEM
FLOWER
FRUIT
NODE
NODE
NODE
INTER- NODE
TERMINAL BUD AXILLARY BUD
SHOOT SYSTEM
Root cap
• Each root tip is covered by a root cap.
• The function of the root cap is to cover and protect the delicate growing tip from injury and damage as the root pushes its way through the soil.
Root hairs
• Root hairs are tiny projections and outgrowths on the outermost layer of the root epidermis.
• The root hairs increase absorption of water and minerals near the root tip.
Looks like a tangled mass of roots
Examples of plants With this root system are Rice Corn Sugar Cane
Fibrous root • A fibrous root system - to many roots
of the same size developing from the end of the stem, with smaller lateral roots branching off these roots.
• Fibrous root systems, which are located relatively close to the surface of the soil, are adapted to obtain rainwater from a larger area as it drains into the soil.
• Monocots most often have fibrous roots.
Have a large main central root
Have many branching roots
Go deep in the soil
Examples of plants : Large trees e.g. mango, avocado Shrubs e.g. tomato, peppers
• A taproot system - one main root with many smaller lateral roots. Lateral roots often initially occur in regular rows along the length of the main root.
• Taproot systems often extend down into the soil to obtain water located deep underground
Roots : - anchor plants firmly in the ground - absorb water and minerals from the soil
- Storage - some plants, can store starch
- of some plants can be used to grow a new plant
Question
• Name the two organ systems and three basic organs found in all plants.
• What are root hairs and what is the function of root hairs?
• Briefly explain the fibrous root. • Describe the functions of roots.
Summary • The root system is generally underground
and obtains water and dissolved nutrient minerals for the plant.
• Root also anchor the plant firmly in place. • A tap root system has one main root from
which many smaller lateral roots extend. • A fibrous root system has several to many
oots of the same size developing from the end of the stem.
The shoot system above – ground portion
The shoot system consists of stems, leaves, flowers and fruits that contain
seeds. And the growth occurs at
apex. Some stems grow
underground – Bulbs and rhizomes etc. They may be swollen to store food
e.g. potatoes.
Woody Plant Stem The stems support the leaves and flowers. In the case of a tree, the stems are the trunk and all the branches, including the smallest twigs.
External stem structure • Stems all have buds,
which are undeveloped embryonic shoots.
• A terminal bud (apical) is the embryonic shoot located at the tip of a stem.
• Axillary buds, also called lateral buds, are located in the axils of a plant’s leaves.
External stem structure • When terminal and
Axillary buds grow, they form stems that bear leaves and/or flowers.
• The area on a stem where each leaf is attached is called a node, and the region between two successive nodes is an internode.
External Stem Structure
• Terminal bud = Extends the shoot system during the growing season
• Axillary bud = Develops into branches with leaves or may form flowers
• Node = Point of attachment of leaf to stem
• Internode = Area of stem between two nodes
• Annual –complete their life cycle in a single year or less (grains, legumes)
• Biennials - (such as carrot, cabbage) take two years to complete their life cycles before dying. In the first season they produce extra carbohydrates, which they store and use during their second year when they typically form flowers and reproduce.
• Perennials – plants that live and reproduce for more than two years. They include trees, shrubs, but herbs can also be perennial.
Leaves
Leaves may be round, needle-like, scale like, heart-shaped, fan-shaped, or thin and narrow. They vary in size, colour, texture.
Tendrils
Mayapple
EXTERNAL ANATOMY • Leaves possess a blade or lamina, an edge
called the margin of the leaf, the veins (vascular bundles), a petiole, and two appendages at the base of the petiole called the stipules.
margin
Structure
The petiole, which joins the leaf to a stem node.
Some leaf blades are attached directly to the stem and lack a petiole or stipules. These are termed sessile leaves.
Structure • In the absence of
petioles in grasses and many other monocots, the base of the leaf forms a sheath that envelops the stem. Some monocots, including palm trees, do have petioles.
Structure • The arrangement of
veins, differ in monocots and dicots.
• Most monocots have parallel major veins that run the length of the blade, while dicot leaves have a multi-branched network of major veins.
veins
Function of leaves
• Photosynthesis • Transpiration - 99% of water absorbed
by plant is lost by transpiration • Exchange of gases –
oxygen and carbon dioxide
What is the difference between deciduous and evergreen?
• Deciduous - they shed all their leaves at
the same time and produce new leaves the following rainy season.
• Evergreen - shed their leaves over a long time period, so that some leaves are always present.
Summary • The shoot system is generally aerial and
obtains sunlight and exchanges gases such as carbon dioxide and oxygen – The shoot system consists of a vertical stem
that bears leaves (the main organs of photosynthesis) and reproductive structures (in flowering plants, flowers and fruits).
– Buds (undeveloped embryonic shoots) develop on stems.
Summary • Buds are undeveloped embryonic shoots. A
terminal bud is located at the tip of a stem, whereas axillary buds (lateral buds) are located in leaf axils.
• The area on a stem where each leaf is attached is called a node, and the region of a stem between two successive nodes is an internode.
Summary • Leaves exhibit variation in shape and form. • Leaves typically consist of a broad, flat blade and a stalk-like petiole. Some leaves also possess small, leaf like outgrowths from the base called stipules.
• Leaves may be simple or compound • Leaf arrangement on a stem may be alternate, opposite or whorled
• Leaves may have parallel or netted (either pinnately netted or palmately netted) venation.
Summary • Monocot and dicot leaves can be
distinguished based on their external structure.
• Monocot leaves have parallel venation, whereas dicot leaves have netted venation.
• The main function of stems is support, conduction and production of new living tissues.
The Parts of a Flower
Most flowers have four parts: • sepals, • petals, • stamens, • Pistil or carpel.
Complete flowers
• Complete flowers usually have four parts-sepals, petals, stamens and pistil-which are usually borne on a receptacle.
Incomplete flower
• Incomplete flowers lack one or more of the four part: sepals, petals, stamens, or pistil.
The parts of a flower • Sepals protect the
bud until it opens. • Petals attract
insects. • Stamens make
pollen. • Carpels grow into
fruits which contain the seeds.
Parts of the Flower • Sepals
– Outer covering of the flower bud.
– Protects the stamens and pistils when flower is in bud stage.
– Collectively known as the calyx.
Parts of the Flower • Petals
– Brightly colored – Protects stamen & pistils. – Attracts pollinating
insects. – Collectively called the corolla.
– Collectively sepals (calyx) and petals (corolla) are called the perianth.
Parts of the Flower (Stamen) • Male reproductive part
– Anther • Produces pollen
– Filament • Supports the anther
– Collectively or a group of stamens is the androecium.
Pistil (female)
• Stigma • Style • Carpel (ovary)
• Ovules (eggs)
Collectively or a group of pistil or carpel is known as Gynoecium
Parts of the Flower (Pistil) • Female reproductive part
– Ovary • Enlarged portion at base of pistil • Produces ovules which develop
into seeds – Stigma
• Holds the pollen grains
- Style • Connects the stigma with the ovary. • Where pollen tube grows down to
female sex cells. • Supports the stigma so that it can
be pollinated.
Ovules (eggs)
• The stamens and pistils are considered the essential parts of the complete flower for sexual reproduction.
• The sepal (calyx) and the petals (corolla) are accessory flower parts.
• A flower with both stamen and pistil (carpel) are considered as perfect flower.
• Imperfect flower has either one but not both.
Petals Stigma
Anther Filament
Ovary
Sepals
Ovules Nectaries
Style
Collect a cut-out flower, colour it in and put it together.
Carpelfemale parts
Stamen male parts
What do the parts do?
Sepals- protect the flower when it is a bud
Petals- colourful to attract the insects
Nectaries- give out sugary liquid to attract insects
Stamen- anther produces male sex cells (pollen)
stigma traps pollen
Style is where pollen tube grows down to female sex cells.
ovary produces female sex cells (ovules)
Flowers
• Function – Contain the sexual
organs for the plant. – Produces fruit, which
protects, nourishes and carries seeds.
– Attracts insects for pollination.
Quick Test 1. Name the parts of a flower that
attract insects. 2. Name the male part of a flower. 3. Which part of the flower contains
ovules? 4. Which part of the flower produces
pollen? 5. Which part of a flower catches
pollen grains?
SUMMARY •A flower may contain sepals, petals, stamens, and carpel (pistils). •Sepals cover and protect the flower parts when the flower is a bud. •Petals play an important role in attracting animal pollinators to the flower. •Stamens produce pollen grains. •Each pistil has three sections: a stigma, on which the pollen grains land; a style, through which the pollen tube grows; and an ovary that contains one or more ovules.
Pollination
• Pollination involves the transfer of pollen (male gamete) from the anther to the stigma (outermost female part)
• Plants are pollinated by insects
or the wind.
Pollination
Self-pollination • Pollen from the
anther is transferred to the stigma in the same flower or a different flower on the same plant
Cross Pollination
• Pollen from the anther of one plant is transferred to the stigma of a different plant of the same species
1. Insect-pollinated flowers may have:
• Brightly coloured petals- blue or
yellow petals.
• Strong sweet fragrance
• Nectar producing glands
• Guidelines to lead insects to Nectar
• Stamen are inside
• Stigma and pollen are sticky
Mode of Pollination
2. Wind-pollinated flowers may have:
• Large stigmas outside the flower
• Little or no fragrance
• Light non-sticky pollen
• Lack showy petals
Mode of Pollination (Continued)
5. Water-pollinated flowers may have:
• Pollen which floats on water
(this form of pollination is rare)
4. Mammal-pollinated flowers may have:
• White flowers
• Strong fruity odour
• Flowers opening at night
3. Bird-pollinated flowers may have:
• Long tube shaped flowers
• Bright red and yellow flowers
• No odour
Feature Reason
small petals, often brown or dull green
no need to attract insects
no scent no need to attract insects
no nectar no need to attract insects
pollen produced in great quantities
because most does not reach another flower
pollen very light and smooth so it can be blown in the wind
anthers loosely attached and dangle out
to release pollen into the wind
stigma hangs outside the flower
to catch the drifting pollen
stigma feathery or net like to catch the drifting pollen
Wind Pollinated Flowers
Feature Reason
large, brightly coloured petals to attract insects
often sweetly scented to attract insects
usually contain nectar to attract insects
moderate quantity of pollen less wastage than with wind pollination
pollen often sticky or spiky to stick to insects
anthers firm and inside flower to brush against insects
stigma inside the flower so that the insect brushes against it
stigma has sticky coating pollen sticks to it
Insect Pollinated Flowers
Pollination Summary
Structure Wind Pollinated
Insect Pollinated
Petals
Pollen
Stamen
Stigma
nectar
dull
light
dangling
feathery
none
bright colour
sticky
inside flower
sticky
makes sugar
Fertilisation
• Fertilisation involves the fusion of the nucleus of the male gamete (in the pollen) with the nucleus of the female gamete (in the ovules).
Fertilisation • Pollen grains
germinate on the stigma, growing down the style to reach an ovule.
• Fertilised ovules develop into seeds.
• The ovary enlarges to form the flesh of the fruit and to protect the ovary.
Seed dispersal Seeds are dispersed in many different ways: • Wind • Explosion • Water • Animals • Birds • Scatter
Seeds must be carried away (dispersed / scattered) from the parent plant to:
• Reduce overcrowding
Seed Dispersal- why?
• Reduce competition for:
- Water
- Light
- Nutrients
What is a benefit of a seed being dispersed far away from
parent plant? • This helps to raise the offsprings
chance of survival, at the same time ensuring the parent plants survival.
• If the seeds land close to the parent plant competition for resources such as water, sunlight, and nutrients will take place, weakening both the offspring plants as well as the parent plant.
How birds and animals help seed dispersal
• Some seeds are
hidden in the ground as a winter store.
• Some fruits have hooks on them and cling to fur or clothes.
How birds and animals help seed dispersal
• Birds and animals
eat the fruits and excrete the seeds away from the parent plant.
Seed Dispersal
Dispersal method
Description Seeds/ Fruits
Wind Seeds are designed to travel as far as possible. May have extensions which act as parachutes or wings. Fruits may be shaken like a pepper pot.
Quick Test-A
1. What term is used to describe male and female gametes?
2. What is pollination? 3. Name the two types of pollination. 4. Describe the differences in the pollen
between insect and wind pollinated plants.
5. Explain why the stigmas of wind pollinated flowers hang outside the flowers.
Quick test-B 1. Why do wind pollinated flowers not
produce nectar? 2. How does the male gamete reach the
female gamete? 3. What is a fruit? 4. Name three ways in which fruits and
seeds are dispersed. 5. Why is it important that fruits and
seeds are carried away from the parent plant?
Summary • Pollination is the transfer of pollen grains from
anther to stigma. • Flowers pollinated by insects are often yellow or
blue and possess a scent. • Bird-pollinated flowers are often yellow, orange
or red and do not have a strong scent. • Bat-pollinated flowers often have dusky white
petals and possess a scent. • Plants pollinated by wind often have smaller petals
or lack petals altogether and do not produce a scent or nectar; wind-pollinated flowers make copious amounts of pollen.