Plants

• Factors affecting plant growth

  Different factors can provide reasons for the results we get from measuring plant distributions
• Temperature


  • Important within photosynthesis
  • Optimum temperature is 45C as the enzymes have the most kinetic energy
  • Higher than 45 C is too warm for the enzymes and their active sites will deform, causing the rate of photosynthesis to decrease
  • If temperatures are too low the plant will not grow and it will die as the enzymes will not have enough energy to perform photosynthesis or the rate will be too low
• Human factor


  • Small plants and tree shoots can be trampled on either killing the plants or limiting their growth due to woodlands and walking paths
  • Pollution, felling, fracking and deforestation all contribute to the disruption of plant growth and distribution
• Mineral ions


  • Different minerals are needed for different elements of plant growth
  • Nitrates = proteins
  • Magnesium ions = chlorophyll
  • Phosphorus = DNA
  • Soils with low mineral concentrations can be enhanced with fertilizers
  • Some plants have adapted to living in a low mineral environment
  • Leguminous plants contain root nodules that convert nitrogen gas in air into nitrates the plant can use to produce proteins in order to grow
• Presence of water


  • Water is needed for photosynthesis
  • Majority of plants need moist soil and regular rainfall to grow successfully
  • Xerophytes are plants that grow in environments with little water availability and have adaptations like waxy cuticles and leaves with a small surface area to prevent excess water loss
  • Cacti are xerophytes
• Light intensity


  • Light is needed for photosynthesis
  • An increase in light intensity increases the rate of photosynthesis due to the increase in provided energy
  • Tall plants create a lot of shade so some plants develop shade tolerance and are adapted to grow at lower levels of light intensity
  • Plants that grow in the direct light need adaptations to deal with the high levels of light intensity so they don't dry out, like UV-absorbing pigments and waxy cuticles
• Soil pH and aeration

  • Most plants grow in a pH range of 5-7, some require acidic or alkaline soils
  • pH in soil can be affected by acid rain, uses of fertilizers and weathering of rocks
  • Some plants need adaptations to grow in soils with low aeration, e.g. rice plant roots grow submerged in water and contain a spongy tissue called aerenchyma that allows low resistance gas exchange between the above water and submerged parts of the plant
• Quadrats


  1m squared, square frame divided into 100 squares, each square represents 1% of the total area of the quadrat, if more than half of a square is covered then it is counted as 1% of the quadrat
• Quadrats


  • Used to count the population size within a large area
• Point frames


  Contain 10 pins, if used with a quadrat then any plant species that touches each pin must be noted down, used to measure the plant cover and distribution
• Sampling


  A small section of the total area, by taking a sample then this allows the population size to be estimated, samples must be accurately representative of the total population size
• Random sampling

  Can be applied by dividing the area of interest into a grid and labelling the grid with coordinates, a random number generator will provide a set of coordinates, quadrats are then placed using the coordinates
• Transects


  A line across habitat, usually placed using a tape measure, used when there is a change, or gradient in abiotic conditions across the habitat, quadrats can be placed at regular intervals along a transect, used when looking for changes in abundance or distribution of a species across the environment
• Line transect

  Records the species that make contact with tape measure at regular intervals along the transect
• Belt transect


  Uses quadrats, the quadrats are placed at regular intervals along the transect, an abundance of different species in the quadrat can be measured by percentage cover (estimate how much of the quadrat is covered by a particular species) or frequency (count how many individuals of a particular species are present in the quadrat)
• The population size of immobile (plants) can be estimated using random samples of quadrats
• Quadrats


  Used to measure the cover of plant species across habitats
• Quadrat placement


  1. Quadrants placed out at set intervals along a line

  2. Quadrant is 1m2 and covers more than half a square

  3. Quadrant is placed on the ground, wherever plant cover is to be counted
• Quadrats


  • Provide information on plant species abundance
  • Provide information on plant species across habitats
• Random sampling


  Sampling method used when time is limited
• Human factors that can benefit plant growth

  • Soil pH adjustment
  • Soil aeration
  • Optimising watering
• Human factors that can disadvantage plant growth

  • Soil acidification
  • Habitat destruction
  • Temperature changes
• Point frame


  1. 10 pins are lowered onto the vegetation

  2. Each plant species touched by the pins is counted
• Optimum temperature

  The temperature at which plant species grow best
• Random number generator

  Used with quadrats and transects to give coordinates for where they can be placed
• Line transect


  • Tape measure set up across the area to be sampled
  • Plant species are recorded along the transect
• Continued sampling

  Species can be recorded at set intervals along the line transect