Plant structures and their functions

• What is the inverse square law equation?

  Inew = (Iorig x Dorig(squared))/Dnew(squared)

  I=light intensity

  D= distance
• What is the inverse square law?

  The inverse square law states that the intensity of a physical quantity decreases with the square of the distance from the source.For example, when a light is moved twice as far away from a plant, it will receive a quarter of the energy
• What’s transpiration?


  The loss of water through the stomata found on the underside of leaves
• What does the xylem transfer and how?

  Water and nutrients; through capillary action and transpiration.Flow is one directional.
• What does the phloem transport?

  Sugars and other organic molecules.
• How does the phloem transport sucrose?

  The sucrose is transported through living sieve cells. Companion cells provide the energy needed for actively transporting sucrose into the sieve cells and are then taking to sinks in the plant where sucrose is needed. The flow is bi directional
• What are the layers in a leaf?

  Waxy coating, upper epidermis, palisade layer, air spaces, spongy layer, lower epidermis, guard cells
• What is the point of the waxy coating in a leaf?

  Keeps water inside
• What does the upper epidermis contain?

  Tightly packed cells
• what is the point of the palisade layer?


  Does most of the photosynthesis as it has all the chlorophyll
• What is the point of the air spaces in the leaf?

  To exchange gases with the air
• What does the lower epidermis contain?

  Stomata and guard cells.
• What is tropism?


  Growth response of a plant to a stimulus.
• Why do root hair cells have an extension?

  to increase surface area to absorb more water and mineral ions
• what are xerophytes?


  Plants adapted to dry environments.
• Whats some examples of physical plant adaptions?

  Thorns, spines, and waxy cuticle.
• What are some examples of chemical plant adaptions?

  Heat exchangers, distillation columns, reactors.
• Where are auxins produced?

  In the tips of shoots and roots
• What are auxins and gibberelins used for agriculturally?

  Weed killer
• What’s the equation for photosynthesis?

  6CO2 + 6H2O + light energy → C6H12O6 + 6O2

  carbon dioxide + water -> glucose + oxygen
• Is photosynthesis endo or exothermic?

  Endothermic
• What is a limiting factor?

  A factor that prevents the rate increasing
• What are gibberellins?

  Plant hormones that promote stem elongation and fruit growth.
• How do you investigate the rate of photosynthesis?


  1~ put some pondweed in a conical flask that contains water and sodium hydrogen carbonate, put a bong in the flask and connect a gas syringe. Then use a ruler to put a white light source a set distance away

  2~ leave the pondweed to photosynthesise for a set amount of time. As it photosynthesises, oxygen will be collected in the gas syringe, note the value of gas collected after the time is done.

  3~ repeat this experiment, moving the light source each time and noting down the volume of gas produced.
• What are the key facts about the Phloem?

  ~bidirectional flow

  ~transports food substances made in the leaves for the rest of the plant (can be used immediately or stored)

  ~translocation

  ~made of elongated living cells
• What are the key facts about the xylem?

  ~made of cells joined together by lignin

  ~carries water and mineral ions from the roots to the stems and leaves
• What is transpiration?


  When plants open their stomata to let in carbon dioxide, the water on the surface of the cells of the spongy mesophyll and palisade mesophyll evaporates and diffuses out of the leaf. Water is then drawn from the xylem to replace the water loss in the leaves
• What are the adaptations of leaves?

  ~Palisade layer = lots of chloroplasts for photosynthesis

  ~upper epidermis = transparent so light can get through to the palisade layer

  ~spongy mesothelioma = contains air spaces which increases the rate of diffusion of gases into and out of the leaf cells

  ~lower epidermis has lots of stomata which lets CO2 diffuse directly into the leaf
• What are the key facts about phototropism in the shoots?

  ~shoots are positively phototropism (grows towards the light)

  • when a shoot is exposed to the light, auxins accumulate in the shaded area, so the plant grows towards the light
• What are the key facts about gravitropism in the shoots?

  ~shoots are negatively gravitrophic

  • More auxins are produced in the lower side due to gravity, this causes that side to grow faster, bending the shoot upwards
• What are the key facts about phototropism in the roots?

  ~roots are negatively phototropic

  • More auxins accumulate on the shaded side so the root grows downwards
• What are the key facts of gravitropism in the roots?

  ~roots are positively gravitropic

  • Gravity also makes auxins accumulate on the lower side, however in the roots, auxins inhibit growth, so the upper side grows faster, angling the root downwards