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Flowering Plants


Introduction to the topic


This standard is about the life cycles of flowering plants. Flowers are the plant's reproductive structures. Angiosperms are types of plants that bear fruits and flowers. Flowers are usually both male and female, and are brightly colored to attract insects/birds or animals to help them carry pollen used for sexual reproduction. Not all flowers are colourful, though. These flowers usually use the wind for pollination.

Before you start

Here is an excellent powerpoint for the topic from Mrs Loughnane here

Start here to see what you know already of the basics. Some excellent study notes from No Brain too small can be found here.

Make sure you practice as many NCEA questions as you can, paying attention to the language in the mark schedules before the exam. Here is an excellent set of notes you can read through.

Mrs C Gren is often used to think about living organisms. Have a look at the following table and compare plants to animals.


Plants

Animals

Movement

Plants stay in one place and parts of them respond to different stimuli. This can be due to growth or just movement.

Animals can move freely

Respiration

Energy production: occurs all the time

Energy production: occurs all the time

Sensing

Have no sense organs but do respond to the environment usually driven by chemicals.

Have specialised sense organs

Cells

Tissues and organs are made of cells

Tissues and organs are made of cells

Growth

Growth is controlled by hormones

Growth is controlled by hormones

Reproductions

Sexual or asexual depending on surroundings and species

Sexual or asexual reproduction may occur but usually sexually

Excretion

Waster products go into surroundings

Waste products go into surroundings but usually through specialised structures

Nutrition

Make their own food for energy

Have to consumes food for energy


Sexual vs. Asexual reproduction - General


Before we start on plants lets think about sexual and asexual reproduction in organisms.

YouTube Video

YouTube Video


Asexual and sexual reproduction of flowering plants (including dispersal)


Sexual Reproduction

In plants this occurs when the pollen from an anther is transferred to the stigma. Plants can fertilize themselves: called self-fertilization. Self-fertilization occurs when the pollen from an anther fertilizes the eggs on the same flower. Cross-fertilization occurs when the pollen is transferred to the stigma of an entirely different plant.

·        Sexual reproduction involved flowering plants (two parents). They use meiosis to produce pollen and ova, which during fertilisation combine to form a seed.

·        Sexual reproduction in plants involves pollen being transferred (pollination) onto a stigma and subsequent fertilisation. In asexual reproduction there is no pollen transfer and therefore no fertilisation.

When the ovules are fertilized, they will develop into seeds. The petals of the flower fall off leaving only the ovary behind, which will develop into a fruit. There are many different kinds of fruits, including apples and oranges and peaches. A fruit is any structure that encloses and protects a seed, so fruits are also "helicopters" and acorns, and bean pods. When you eat a fruit, you are actually eating the ovary of the flower.

Notes covering the topic
Online lesson on plant reproduction
A great animation to start

A plant produced by sexual reproduction has a different genetic makeup from its parent plants.
Sexual reproduction begins with the production of flowers by the adult plant.˜ (male gametes) forms 
by meiosis in the anther of the flower. female gametes) form in the ovary



Pollination: The transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower. Pollination is needed for fertilization: the fusion of nuclei from the pollen grain with nuclei in the ovule. Fertilization allows the flower to develop seeds. 
Some flowers will develop seeds as a result of self-pollination, when pollen and pistil are from the same plant, often (but not always) from the same flower. Other plants require cross-pollination: pollen and pistil must be from different plants.

Description of insect-pollinated features:

· colourful petals
· scent and nectar
· anthers and stigma located inside flower
· sticky pollen

Description of wind-pollinated features:

· anthers and stigma dangle outside flower
· large anthers and stigma
· anthers produce large amounts of pollen
· smooth, light pollen

Explanation of how features enable insect-pollination:

· colourful petals attract insects, which have colour vision
· nectar attracts insects to the flower to feed
· the sticky pollen attaches to the insect so it can be transferred

Explanation of how features enable wind-pollination:

· anthers dangle outside flower to that pollen can be released into the wind
· the stigma is large to increase the chance that it will catch passing pollen
· the pollen is light so that the wind is easily able to carry it

Features that can be compared/ contrasted:

· physical characteristics of flowers (colour, scent, size and smell)
· relative size of sex organs
· location of sex organs
· volume of pollen produced
· nature of pollen produced (surface and size)

Eg, Wind pollinated plants produce considerably more pollen than insect pollinated plants. A large amount of pollen is lost in the wind and does not reach the stigma of a flower. Equally the pollen must be light so that the wind is able to carry it. Insect pollinated plants are able to produce less pollen, as less is lost by the action of insects carrying it from one flower to the next. The pollen is sticky so that it is able to adhere to the insect for transportation.

The Perfect Flower (From Sepals to Ovules)

This is based on the perfect flower, of course all flowers are different.  Let's start with the outside of the flower. The first things you see are probably its Sepals and Petals.

The Sepals form a ring of small leaf-like sections around the base of the flower. They are usually green and their job is to protect and support the flower.

The bright-colored Petals are there to attract the birds and insects who will do the important work of pollination (we'll tell you more about pollination in a minute). The Petals often smell good, too. (Some flowers depend on the wind for pollination, so their Petals are less colorful & fragrant since they don't need to attract pollinators).

The Petals form the plant's Corolla, while the Sepals form its Calyx.

Now let's peel back the Petals and look inside the Corolla.

What do you see?

First, you'll probably see some slender stalks with little grain-like things at the ends of them. The stalks are Filaments and the little things on the ends of them are Anthers. The Anther and the Filament are the male reproductive organs of the flower. Together, they are called the Stamen.

The plant's male sex cells, a powdery substance called Pollen, are formed inside the Anthers.

What else will you see inside the flower?

Well, deep in the center of the Corolla, you will see the plant's female reproductive organs. Each of these organs is called a Carpel -- and all the Carpels together are called the Pistil.

Each Carpel consists of a Stigma, a Style and an Ovary.

The Ovary is located at the base of the flower -- and this where the plant's female sex cells (called Ovules) are produced. The Style is a tube on top of the Ovary and the Stigma is the top part of the Style. The Stigma is where Pollen sticks during fertilization.

Obviously, for fertilization to take place, Pollen from the male part of a plant -- the Stamen -- must reach the Ovule deep inside the female part of a plant, the Carpel (Pistil).

It’s the plant equivalent of human sperm fertilizing a human egg. In plants, the process is called pollination.

Leaves

The most important function of the leaf is to make food for the plant. The two main parts of a leaf are the leaf stalk, called the petiole, and the flat leaf blade. Inside the blade you can see a pattern of leaf veins. The veins carry food and water.

Asexual reproduction

Asexual reproduction produces genetically identical offspring because there is no fertilisation. Sexual reproduction produces genetically unique offspring as a result of meiosis and fertilisation.



Examples

· Potato plants reproduce asexually using stem tubers or tubers. 

· Strawberry plants reproduce asexually by producing horizontal stems called runners. 

· Garlic plants reproduce asexually by producing bulbs. 

· Ginger plants reproduce asexually by producing swollen horizontal underground stems called rhizomes. 

· Dahlia plants reproduce asexually by producing swollen root tubers. 

· Gladiolus plants reproduce asexually by producing stacks of stem bases called corms. Lilac plants can reproduce asexually by producing adventitious shoots from lateral stems that touch the soil. This method is called layering.

Asexual reproduction is also called vegetative reproduction in some NCEA questions. It involves production of new plants without the making of seeds or growth from seeds. A plant produced by asexual reproduction has the same genetic makeup as the parent plant (clone). Asexual reproduction is fast and does not require a plant to use energy to make flowers, pollen and fruits which is more efficient but they do lack variation which can be a bad thing if disease hits.  A large number of offspring that grow close to the parent plant are produced. Many plants that reproduce  asexually also reproduce sexually at a different time of the year.

eg. ·        A [strawberry] plant reproduces asexually by producing [runners]. These grow by mitosis from existing tissue in the plant (single parent).

Asexual propagation.


YouTube Video



YouTube Video


Meiosis


Meiosis gives rise to variation. This is an important part of sexual reproduction. The variation produced is inherited, which means that evolution can take place as a result of the natural selection of certain variants to suit a changing environment. The way that meiosis gives rise to variation is by recombining genes from chromosomes in new ways. When the number of chromosomes is halved, there is some randomness in the way parts of chromosomes are selected to go into the gametes. 

YouTube Video


Germination and growth (including development such as flowering, primary and secondary growth and photosynthesis).


Notes on Flower reproduction

Another good starting activity 

Growth

The growing parts of plants are actively dividing by mitosis to make new cells and tissues. These tissues elongate and specialise. However, in root tips the division and elongation of cells results in the root growing downwards (positive geotropism) towards a source of water, while in the shoot tip the division and elongation of cells the shoot tip to grow towards the light (positive phototropism) necessary for photosynthesis.Once the new cells are produced they elongate and become bigger, and then differentiate into the specialised cells and tissues required by the plant. This process occurs in both root and shoot tips. In root tips, however, the cells may become, for example, root hair cells for increased water absorption or root cap cells that secrete a protective slime to ease the passage of the root tip through the soil as it grows. In shoots, the cells may differentiate into, for example leaf epidermal cells that develop a waxy cuticle for water conservation, or leaf palisade cells with many chloroplasts for photosynthesis.

Biological ideas relating to the life cycle of flowering plants will be selected from

A great introduction to life cycles 

related life processes

Photosynthesis


An excellent interactive workshop can be found here


Photosynthesis is a process by which light energy is converted into chemical energy.This process consists of a series of chemical reactions that require carbon dioxide (CO2) and water (H2O) and store chemical energy in the form of sugar. Light energy from light drives the reactions. Oxygen (O2) is a byproduct of photosynthesis and is released into the atmosphere. The following equation summarizes photosynthesis:
6 CO2 + 6 H2O → 6(CH2O) + 6 O2
sugar

Plant Cell Tutorial
A great starter animation here

Photosynthesis & Cellular Respiration

Some excellent notes on Photosynthesis. Photosynthesis in detail

Now have a look at the following animation.

Photosynthesis animation Click here
More advanced animation here
Where & How p/s occurs in a leaf
Photosynthesis

The important parts of the plant and how they relate to photosynthesis.


Why is this important for photosynthesis?

Spongy layer leaving air spaces

Still carry out photosynthesis but the spaces allow gases to move around them (O2 and CO2)

Stomata and guard cells at the bottom

If the stomata were on the top of the leaf, water (that is vital in the process of photosynthesis) would be lost by transpiration

Leaves are flat and thin

The flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide.

Chloroplasts are mostly at the top of the leaf

So they can be exposed to as much sunlight as possible to carry out photosynthesis

Vascular bundles containing xylem and phloem

Xylem transports water to the cells, phloem transports the glucose away


YouTube Video


Primary and secondary Growth 


An excellent website can be found here


Nutrition and transport


YouTube Video


Structural components involved with the plant processes


animation linking structures to processes

 the functioning of the structural components

YouTube Video


·       the overall functioning of the plant processes

·       products or outcomes of the plant processes (including raw materials and requirements)

·       the effect of environmental factors, such as light intensity, temperature, wind, moisture and oxygen, on the selected plant processes.


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