This course is about the NCEA Level 1 external in Biology, Life Cycle of Flowering Plants. This course is made so I can study for the exam, however, anyone is welcome to use it. There will be different sections you will work through. These sections will include slides, mind maps, flow charts, quizzes, text and Flash cards. It will also include practice exam questions that you should try your-self!
Thank you for using this as a resource for studying!
Growth is a characteristic of all things living. Growth means the production of new cells, usually accompanied by an increase in body size. Plants grow rather differently from animals.
A typical plant consists of two parts - a root system that absorbs water and minerals and a shoot system that uses light energy to convert Carbon Dioxide and water into carbohydrates by photosynthesis. The roots and shoots are interdependent - The shoots depend on the roots for water and minerals, the roots depend on the shoots for energy in the form of carbohydrates.
A fully-developed shoot system consists of stem-bearing leaves. The leaves arise from points called nodes; the region between nodes is called an internode.
At the tip of the shoot, the young leaves are very small and clustered together to form a terminal bud. The stalk of a leaf is the petiole, and the angle between a petiole and the stem is the leaf axil. In each Axil, there is an axillary bud., which can grow out into a side shoot.
Produces pollen, which contains the sperm cells.
The collective name for the anther and filament.
Often large and coloured to attract pollinators. Collectively called the corolla.
Contains the ovules. Develops into fruit after fertilisation.
The long hollow tube connecting the stigma and ovary.
Produces nectar to attract pollinators.
Contains an egg cell and develops into a seed after fertilisation.
Protect the bud before it opens. Collectively called the calyx.
The sticky surface where pollen lands and germinates.
Long stalk which holds the anther in the correct position for pollination.
Primary growth is the first growth of a plant. It is when the plant grows upwards/downwards to make the plant longer. In contrast, secondary growth is the outwards growth of the plant to make it thicker/wider.
There are three basic stages of primary growth:
Cell division - cells divide by mitosis to produce more cells
Cell enlargement - cells get bigger
Specialisation - cells differentiate (change to suit a particular job)
Plants grow at the tips of their shoots and roots, so these are always the youngest parts of the plant. The roots and shoots grow through cell division at areas called apical meristems. The cells produced here then fill with water and grow longer. They will eventually mature and differentiate to become particular types of cells (e.g. skin cells, leaf cells, root hair cells). Because the cells in an apical meristem can become any type of cell, they are called stem cells.
In a young stem, substances are transferred around the plant in vascular bundles. These contain three types of cells:
Xylem - transports water from the roots to the rest of the plant.
Phloem - transports sugar from the leaves to the other parts of the plant which need glucose.
Vascular Cambium - stem cells which will produce secondary growth
Hormones are chemicals which are used by living things to send messages between cells. We have hormones such as testosterone, adrenaline and insulin which tell our body to do certain things. Plants also have hormones to coordinate different processes.
The plant hormone auxin coordinates primary growth. It allows the shoot to grow upwards and towards the light and the roots to grow downwards. It acts in different ways on different parts of the plant (i.e. shoots and roots): it accelerates growth in the shoot but slows growth in root cells.
Auxin moves downwards through plant cells. In a shoot, this makes the cells at the bottom grow longer, which turns the shoot upwards.
However, in roots auxin makes the cells on the bottom edge elongate more slowly, which makes the root grow downwards.
So no matter which way up a seed is planted, its shoots will always grow up away from gravity and the roots will always grow down towards gravity.
In shoots (leafy part of the plant) auxin also stimulates growth towards the light. Auxin is produced at the tip of the plant and filters downwards through the stem. It will move away from light, stimulating more growth on the darker side and resulting in the tip of the shoot bending towards the light.
Sensitivity means being able to sense changes in the environment. A stimulus is a change in the environment which produces a response (e.g. the bell is a stimulus which causes your response – to pack up!).
One way plants respond to their environment is with tropisms. This is a growth response to a stimulus (e.g. light, gravity, touch).
Tropisms can be:
positive: growth towards the stimulus
negative: growth away from the stimulus
We have names for tropisms caused by different stimuli:
For example, growth towards light is called positive phototropism. Growth away from gravity is called negative gravitropism.