Biology—>Transport in plants

• When is translocation higher?

  On warm sunny days when plants are producing more sugar
• Why can water move up the xylem only in one way?

  Because transpiration always happens at the leaf surface and it is this that provides the pull to draw water up the plant
• So what is the overall system of sources and sinks, in all the seasons?


  In summe the leaves are sources, and the growing stem tubers are sinks

  in spring The stem tubers are sources, and the growing leaves are sinks.
• What happens in Spring?

  They begin to grow new shoots and leaves

  the starch in the tubers change back into sucrose and transported in the phloem into the growing stems and leaves. This will continue until the leaves are above ground and photosynthesize
• What happens in autumn?

  In autumn, the leaves die nothing is left of the potato plant above ground

  just the stem tubers beneath the soil.
• What happens during the summer?

  The leaves photosynthesize and , send sucrose down into underground stems,

  Here swellings cold tubers develop the cells in the root tubers change the sucrose to starch and store it
• What happens when plants become dormant?

  They wait out harsh conditions in a state of reduced activity dormant plants do not photosynthesize but instead survive on their stored starch, oils, and other materials. When the seasons change, they begin to grow again now the stored materials are converted to sucrose and transported to the growing regions.
• How do flowers use sucrose

  To make fructose
• What happens when a plant is actively photosynthesizing and growing

  The leaves are generally the major sources of translocated materials. They are constantly producing sucrose, which is carried in the phloem to all other parts of the plant.
• Examples of sinks

  Roots /stems-starch is stored here

  Root tips -amino acids are stored here
• Examples of sources

  Leaves-sucrose is produced here

  Root hairs-nitrates are absorbed here
• What are sinks?

  The areas where sucrose is delivered to, and made use of
• What are the sources?

  The areas of the plant where is sucrose is made
• How do growing cells use sucrose

  They make cellulose for cell walls from sucrose and use the amino acids to make proteins for growth
• How do you root cells use sucrose

  Convert sucrose into glucose for respiration and store it
• Are sucrose and amino acids transported to every tissue of the plant

  Yes, if cells use it in a different way
• Where does the phloem transport the sucrose in the leaf?

  All across the leaf where it can be made use of
• In what ways can substances be transported,in phloem?

  From photosynthesizing leaves down to root for storage

  Upwards to growing buds, flowers leaves and fruit for respiration and growth from storage organs, such as the root tubers to all parts of the plant
• What is sucrose used for?

  Can be converted to starch and broken down to glucose

  converted to cellulose for cell membranes

  flowers use the sucrose to synthesize nectar and attract insects
• What are amino acids used for?

  Protein synthesis, growth ,repair

  replacement of old cells, enzymes ,specialized proteins ,structural proteins
• How is phloem bidirectional?

  It can move upwards from fruits to growing buds, flowers, leaves, and fruits for respiration and growth, and from photosynthesizing leaves to roots down to roots for storage
• How are companion cells adapted to their functions ?

  Have a lot of mitochondria to do respiration and release energy to actively transport sucrose into phloem and load it into phloem
• What does phloem have in its end walls?

  Perforations —> sieved plates
• Translocation

  This movement of sucrose and amino acids in phloem, from regions of production (source) to regions of storage or use (sink)
• When measuring transpiration rate is all the water lost to transpiration?

  No, a small amount of water is used in photosynthesis and to maintain a viable turgidity of plant cells
• How does the Potometer work?

  When a plant is affixed to the Potometer transpiration can be indirectly identified by the movement of water towards the plants. This water movement can be assessed by the movement of an air bubble towards the plant

  initial starting position of the air bubble can be adjusted by introducing additional water from a reservoir.
• What is a Potometer ?

  And device that is used to estimate transpiration rates by measuring the rate of water, loss or uptake
• How is the opening and closing of the stomata controlled by guard cells?

  In light guard cells, take up water by osMoses and become Turgid because their inner walls are rigid. They are pulled apart opening the pore

  in darkness water is lost, and the inner walls move together closing the pore because of this transpiration rate is increased by an increase in light intensity.
• How does light intensity increases the rate of transpiration?

  More photosynthesis, so more need for water and more evaporation in between air spaces in spongy messophyl.

  
  

  stomata are open to allow gas exchange for photosynthesis so that carbon dioxide can enter and water vapor can therefore diffuse out of the stomata
• How does humidity decrease the rate of transpiration?

  Decreases the concentration gradient between the air spaces, and the atmosphere, as there are many water vapor particles in the atmosphere, so slower diffusion
• How does wind affect the rate of transpiration?

  Removes water molecules as they pass out of the leaf, giving a steep concentration gradient for diffusion as the water vapor outside they leaf is constantly being removed
• How is transpiration affected by temperature?

  More evaporation, causing a steep concentration gradient between water vapor in the air, spaces and water vapor in the air

  also heat gives the water vapor increase kinetic energy, so water molecules diffuse faster out of the stomata
• What can of rate of transpiration be affected by?

  Temperature, Wind ,humidity, light intensity
• How are amino acids used in plants?

  For proteins synthesis, growth repair, specialized proteins like enzymes
• Why is water needed in cells?

  Transporting mineral ions

  Providing water to cells turgid in order to support the plant

  Providing water to leaf cells for photosynthesis

  Can you bring the leaves cool by evaporation - heat energy causes of operation, so losing heat cools down plant
• Wilting

  Transpiration rate> rate of water absorption
• How does wilting occur?

  Young plant stems and leaves, rely on their cells, being turgid to keep them rigid if the amount of water lost from the leaves of a plant is greater than the amount taken into the roots, the plants will have a water shortage, and the cells become flaccid and will no longer press against each other so stems and leaves lose their rigidity and wilt
• What is wilting due to

  Excessive transpiration
• What is the mechanism by which water moves upward xylem in simple steps

  Transpiration continuously remove the water from the leaf

  This water is constantly being taken from the top of the xylem vessels to supply the cells in the leaf

  This reduces the pressure at the top of the xylem vessels

  This creates a transformational stream, pulling water up

  Water molecules have a strong tendency to stick together. This is cohesion.

  When the water is pulled up the xylem vessels, the whole column of water stays together
• Mechanism by which water moves up in xylem

  Water molecules are attracted to each other by cohesion. Add water vapor evaporating from a leaf creates a suction because the pressure of water at the top of the vessels is lower than that of the bottom. This creates a transpirational pull that draws a column of water molecules up the stem in the xylem so more water is drawn into the leaf from the xylem.