Plant Nutrition and Transport

Plant Nutrition and Transport

  • Water and nutrients are needed to grow and survive
  • Produce their own carbon source (glucose) through photosynthesis
  • Also need carbon dioxide from the air
  • Has evolved mechanisms to ensure they can take up water and nutrients and can be adapted to survive under dry conditions
  • A large maple tree needs 800L of water per day

Water vs Forgot to water

  • With water the plant is turgid
  • Without water plant is wilted

Nutrients

  • Root take up minerals, oxygen, and water, Carbon dioxide leaves through roots
  • Leaves take up carbon dioxide and light and water and oxygen leaves
  • Sugar is being made and transported across the entire plant

Coniferous and Deciduous Trees

  • Coniferous has small needle-like leaves, retain the needles year round
    • Needle-like leaves use less energy to maintain
  • Deciduous trees has broad and flat leaves. It drops the leaves seasonally
    • So it can spend less energy in the winter

Water Movement from Soil to Top

  • Water enters through osmosis
    • Less solute concentration inside the root
  • Water from the soil goes to the xylem of the vascular bundle
  • Next step is to move water Up the plant against gravity

Roots take up water

  • Takes up through osmosis, movement of water form low solute concentration (soil) to high concentration of solute (cell)
  • Root hairs provide increase surface area for absorption of water and nutrients
  • Once water enters, it can move in between cells through apoplast (outside the cell) or through the cells themselves through symplast
  • Once it reaches a layer of cells called endodermis, water is redirected to move via the symplast.
    • Allows for control of water uptake
  • Inside the endodermis is the Casparian strip which is how water movement is regulated
    • Doesn't allow water movement by apoplectic route. Forces to redirect the water so it moves through the sympalst
    • Allows for the cell to not become flooded

Water movement up through the xyelm

  • Cohesion by hydrogen bonding allows for water molecules to stick each other and adhesion allows to stick to the xylem cells

Water movement

  • Inside the xylem tracheid and vessel elements
    • Water molecules adhere to each other by hydrogen bonding as well as to the walls of the xylem vessels
  • Creates a column of water internally
  • Water travels upward to the leaves at a rate of 15m per hour in a large tree

In leaves, there is loss of water through transpiration

  • Water leaves through stoma
  • As water leaves the stoma, water moves in through the roots
  • Loss of a plant's water to its environment through evaporation

Water Flow Up the Plant

  • Loss of water due to transpiration (movement o water out of leaves via stomata) creates a "water deficit" or negative water potential inside the leaf
  • Causes a "pull" of water into the leaf from the xylem. This then pulls water up the xylem from the roots
  • The "pull" is the main force that causes water to move up the plant, from roots to leaves
  • If you cover a plant for 24 hours inside a plastic bag, it is easy to see how much water is release form the leaves into the bag

  • As the concentration of water is lost at the leaves through transpiration, water is then pulled up the xylem from the roots
    • Negative water potential inside the leaf

Transpiration results in water loss

Stomata

  • Need to take open to take up CO2 and release O2 during photosynthesis
  • Only way they regulate what gets in and out
  • When potassium and enough water arr in the guard cells the stoma is open

Functions of Stomata

  • They are found in the epidermal layer of leaf cells
  • There are more stomata on the underside of leaves compared to the upper surface as they are not exposed to direct light and its cooled
  • Guard cells of the stomata regulate the stomatal opening size. Larger the opening, the more water will be lost
  • Stomata will open when there is lots of water, when there is sunlight and when potassium ion levels are high inside guard cell. This causes water to flow in
    • Must fill guard cells in order for stoma to open. When vacuoles fills up the cell expands are forces It open
    • Ensures that excess water that isn't needed is lost
  • Stomata will close when there is not enough water, when it is dark and when potassium levels are low. This causes water to leave the guard cells
    • When vacuoles aren't filled, it can't push against cell well therefore closing the stoma

How do plants survive in Desert Climates

  • Reduced leaf size and fleshy leaves store water
  • During dry seasons, plants can dry down but grow again when it rains
  • Some plants close the stomata during the day, open them at night when it is cooler
  • Stomata may be located deeper inside the leaf than in the epidermis
  • Leaves have thick waxy cuticles to retain water
  • Plants have fewer stomata
  • Plants that live in the desert are called xerophytes

Function of the Phloem

  • During photosynthesis, sugar is produced in the leaves that must be transported to other parts of the plant
  • This requires movement from the sources (leaves to where it is needed for growth)
  • Sugar is loaded into the phloem cells by sucrose transporters. This causes a high osmotic pressure which draws in water from xyelm
  • This causes pressure to build up which forces the flow of sugar down the plant
  • The turgor pressure causes the sugar solution to move via "bulk flow" to reach cells that need it (growing fruit, shoots, roots) the sugar is unloaded here

Know process of phloem sugar loading and unloading

  • Sugar moves from leaf to phloem and is building up
  • Creates osmotic pressure which drives the movement of water up the xylem
  • As pressure builds it forces the flow of sugar down the plant
  • Causes the sugar solution to move by bulk flow to reach cells that need it

Xyelm and phloem

  • Xylem
    • Moves water and nutrients up the plant, from roots through stems to leaves
    • Has cells called tracheid and vessel elements
    • Cells are non-living
  • Phloem
    • Moves sugar and water solution from leaves to other parts of the plant
    • Consists of sieve tube elements and companion cells
    • Are living

Maple Syrup

  • Is the sap from maple trees that is concentrated to make maple syrup. It is boiled to concentrate it to 66-67%
  • Maple syrup is taken as "xylem sap" from trees during early spring
  • In the fall, sugar is transported by the phloem to the roots for the storage. In early spring, temp are above freezing during the daytime, the sap is moved up through the xylem to give energy for leaves to grow.
  • Drilling hole sin the trees allows xylem sap to drip due to positive pressure flow

Mineral Nutrition of Plants

  • Plants need nutrients and the amounts they need are divided in to macronutrients and micronutrients
  • Ion channels allow for nutrients to enter cells