Cymraeg

Crop Production
Session 1 - Basic Plant Physiology

This resource is suitable to support Level 2 Agriculture courses.

Content

This unit on crop physiology will contain information on the following:

  • Session 1 - Basic physiology of plants
  • Session 2 - Plant cell structures and processes
  • Session 3 - Plant life cycles
  • Session 4 - Plant physiology
    • image of green leaves against black background

    Section 1 - Basic Plant Physiology

    Section 1 - Basic Plant Physiology


    Seeds

    A seed consists of a tough coat which is called the ‘testa’ which protects the seed from fungi, bacteria and insects, within the ‘testa’ is the ‘embryo’, which contain the:

  • Plumule – that develops into the leafy part of the plant.
  • Radicle – that develops into a root system.
  • One or two cotyledons – that contain food reserves that are used in germination.

    • Plant Classification According to the Number of Cotyledons

    Plants are classified as either monocotyledons (one cotyledon in the seed) or dicotyledons (two cotyledons in the seed)

    image of a pile of green seeds

    The Structure of the Monocotyledons

    Cereal and grass seeds are monocotyledons (contain one cotyledon). Wheat grain is a typical example:

    diagram of monocotyledon with arrows pointing to Radicle, Skin (Bran), Cotyledon (one in each seed), and Plumule

    The Structure of Dicotyledons

    The broad bean is a typical example of a dicotyledon (contain two cotyledons):

    diagram of dicotyledon with arrows pointing to Cotyledon (of of two), Plumule, and Radicle.

    The Differences Between Monocotyledons and Dicotyledons

    Monocotyledons

  • Embryo has one seed leaf.
  • A primary root system is developed but is then replaced by an adventitious root system.
  • Usually narrow leaved plants, e.g. cereals and grasses.

    • Dicotyledons

  • Embryo has two seed leaf.
  • A primary root system is developed and persists.
  • Usually broad leaved plants, e.g. clovers, cabbage and potatoes.

    • Session 2 - Basic Plant Physiology


    Plant Systems


    Photosynthesis, respiration, transportation, translocation.

    Photosynthesis

    Photosynthesis is the process by which the plant produces its own food.

  • The process takes place in the leaves of all green plants.
  • Chlorophyll is a green substance in leaves that uses light energy to change carbon dioxide and water into glucose and oxygen.
    • image of plant in soil with the sun in the background

    Leaf Cross Section

    graphic of cross section of leaf showing lower leaf surface, stomata, upper leaf surface (cuticle), Cells containing chlorophyll in tiny particles (chloroplasts), and spongy cell tissue

    Glucose

    Glucose is a carbohydrate that stores energy in the plant and is used for growth and development.

  • Oxygen is released by the plant into the atmosphere.

    • The Photosynthesis Process

    Diagram showing photosynthesis process. From left to right: ‘Carbon Dioxide (From atmosphere) + Water (from soil) + Energy (From light)’ arrow with ‘Chlorophyll’ in it, pointing to ‘Glucose (Energy for growth and storage + Oxygen (Released to atmosphere)’

    Respiration

    Respiration is the opposite process to photosynthesis.

  • Cells within plants combine oxygen with carbohydrates such as glucose to release energy, carbon dioxide and water.
  • Carbohydrate + Oxygen = Carbon dioxide + Water + Energy
    • image of leaf basking in sunlight

    Nutrient and Water Uptake

    Water and nutrients are taken into the plant from the soil.

  • This occurs mainly through the root hairs near the root tips, there are thousands of root tips on a single plant.
    • image of plant roots covered in soil

    The Root Hairs on a Root

    image of root hairs on a root

    Root Cross Section

    cross section of root showing Root hairs, Root tip, Root cap, and Xylem

    Water Uptake

    The plant pulls the water in by a suction that starts up in the leaves.

  • As water transpires (evaporates) from the leaves, more water gets drawn up through the xylem tubes.
  • This process is called Transpiration.
    • image of plant in soil showing roots

    What Affects the Absorption of Water from the Soil?

    The rate of absorption is slowed down by:

  • Shortage of water in the soil.
  • Lack of oxygen in soil.
  • A high concentration of salts in the soil water.
    • image of leafy plants in crop

    Transpiration

    Water needs to leave the plant through the leaves in order to create the suction needed to draw up more nutrients from the soil, this process is called transpiration.

  • Water in the cells of the leaf can pass into the air spaces in the leaf and then escapes out through the stomata as vapour.
    • graphic of cells in leaf

    Importance of Transpiration

    This process has two beneficial effects:

  • Transports minerals from the soil.
  • Cools down the plant.
    • image of water droplets on a leaf

    Factors that Affect the Rate of Transpiration

    Factors that maximises the rate of transpiration are:

  • Enough water in the soil.
  • Large amount of sunlight.
  • High temperatures.
  • Lots of air movement.
    • image of lots of green crops with sunlight behind them

    Translocation

    Plants need to transport food and water internally, this process is called translocation.

  • To complete these tasks, the plant has two separate sets of tubes called the xylem and phloem.
  • They both usually run alongside each other.
    • cross section graphic labelling xylem and phloem

    Diagram Showing Stem Cross Section

    stem cross section diagram pointing to Xylem and Phloem, an arrow pointing towards the xylem tube with text 'Water and nutrients from the soil', and an arrow coming from Phloem tube with text 'Sugar fat and protein from the leaves'

    Phloem Tubes

    Phloem tubes are living cells that transport the products of photosynthesis.

  • The tubes transport sugars, fats and proteins made in the leaves to the growing parts of the plant such as the shoot tips and root tips.
  • The food is used for growth or stored.
    • Phloem tube under microscope

    Xylem Tubes

    Xylem tubes take water and minerals from the roots to the leaves.

  • These tubes are made up of dead cells with side walls that are strong and stiff and contain lignin.
  • This gives the plant support.
    • graphic of xylem tube closeup

    Session 3 - Basic Plant Physiology


    Plant Life Cycles


    Germination, initial growth of the plant and key stages of growth.

    Germination and Initial Growth

    Seed germination is triggered by anaerobic conditions, the presence of water and warmth.

  • Most temperate crops need a minimum temperature of 0 - 5°C and an optimum of 20 - 25°C.
  • Cold sensitive crops such as forage maize need a minimum of 8 - 10°C to germinate.
    • image showing 5 seeds in soil, from left to right they are increasinly grown.

    Germination of the Forage Maize Seed ‘ Monocotyledon’ (Ioan Rhys Williams)

    Diagram of germination of 5 foraze maize seeds of increasing growth. Diagram shows Radicle, Fruit wall splits, Plumule in coleoptile, Coleoptile, the last seed shows 'first leaves emerge from top of split coleoptile, prop roots (help support the plant), Adventitious roots and lateral roots.

    Steps in Germination

  • 1. The seed swells with the absorption of water and the radicle bursts through.
  • 2. Radicle grows down between the soil particles, protected by the root cap.
  • 3. Root hair grows on the upper part of the radicle and water and nutrients are absorbed.
  • 4. Food reserves in the cotyledon (starch and protein) are used as energy by the growing regions.
  • 5. The plumule grows straight through the fruit wall (the growing point is protected by the coleoptile, which has a hard, pointed tip).
  • 6. Adventitious roots grow from the base of the plumule.
  • 7. Once the coleoptile is above the soil, the first leaves burst out of it.

    • Dicotyledons: Germination of a bean seed (Ioan Rhys Williams)

    Diagram of germination of bean seed, showing 5 beans of increasing growth. First seed is labelled 'Testa splits, Radicle emerges', third seed is labelled 'Hypocotyl 'elbows' out of soil, Lateral roots', fourth seed is labelled 'Plumule protected between cotyledons', and fifth seed labelled 'Growing point, Cotyledons will fall out'

    Video Showing Germination of a Broad Bean Seed

    Key Stages in Plant Growth

    The main processes of plant growth are:

  • Germination
  • Establishment
  • Vegetative growth
  • Stem extension
  • Anthesis
  • Seed fill
  • Senescence
  • Maturity
    • image of 8 seeds in soil of increasing growth until they are sprouting

    Key stages in cereal crop growth

    image of 7 cereal crop seeds increasingly growing from seed to crop from left to right. Each seed is labelled respectively: Germination, Establishment, Vegetative Growth, Stem extension, Anthesis, Senescence, and Maturity

    What Influences Plant Growth?

    The growth rate of plants is influenced by:

  • The amount of sunlight the plant receives.
  • The ability of the plant to capture sunlight ‘leaf area index’.
  • Soil temperature.
  • Water availability.
    • image of grass in front of blue sky

    Session 4 - Reproduction in the plant; sexual and asexual.

    Reproduction in Plants

    Plants can reproduce either by sexual or asexual means.

    image of tomatoes on vine
    image of potatoes sprouting

    Sexual Reproduction

    Sexual reproduction occurs when pollen produced in the male part of the flower, the stigma, is transferred via insects or wind to the ovules (eggs) that are produced in the female part of the flower, the carpel.

  • Once fertilization has been achieved, the plant produces fruit and seeds that are later dispersed and germinate to produce new plants.
  • This is predominantly how weeds establish in crops.
    • closeup of pollen on flowers

    Asexual Reproduction

    This type of reproduction is also known as ‘vegetative reproduction’.

  • This occurs in plants when they produce a separate plant from side shoots on the stem or roots.
  • No sexual reproduction has taken place so there is no difference between the genetic makeup of the plant and its mother plant.
  • The process in which seed potatoes germinate is an example of this type of germination.
    • image of 2 potatoes with roots growing out of them

    Advantages of Asexual Reproduction

    Advantages

  • Very strong start, parent plant are a strong source of nutrient and water.
  • Difficult to kill, food store is not easily destroyed.
  • Cultivation can spread the plant by chopping up the food store.
  • Genetic makeup is not changed.
    • image of leafy plant

    Disadvantages of Sexual Reproduction

    Disadvantages

  • The new plants are sited close to the parent plant and will compete for the same food and water.
  • Plants do not spread very far.
  • No possibility of genetic improvement.
  • Viral diseases transmitted to the offspring.
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