Please enable JavaScript.
Coggle requires JavaScript to display documents.
Plant biology AHL (Plant growth (Dermal tissue (Protects from water loss…
Plant biology AHL
Plant growth
-
Ground tissue
Tissue made up of cells made up of thin walls, assists with photosynthesis
-
All of the above are made up of meristamatic tissue, which are similar to human stem cells. when dividing, one becomes meristamatic, one differentiaties.
Indiscriminate growth
Apical meristem
Found in the roots and forms the shoot apex, which undergoes mitosis and this allows primary growth which is fleshy and non woody in nature
Root apex grows downwards, And Shoot apex grows upwards through terminal bud due to influence of auxin. Auxin only promote growth upwards of wither the shoot or root, but prevent lateral growth. Removal of terminal shoot, results in increased lateral growth.
Lateral Meristem
grows sideways, and is responsible for woody growth
-
-
-
Phloem Transport
Companion Cells
Provide Metabolic support for Sieve cells. Have an in folding Plasma membrane to increase S.A ratio, have meany mitochondria to fuel the active transport of materials through sieve tubes form source or sink
Sieve Cells cannot persist without Companion cells as Companion Cells provide them with nutrients and metabolic requirements.
Sieve cells
Long narrow cells, with their ends being connected in sieve plates, which are porous and allow passage through them. They have no nuclei, and minimum organelles to maximize translocational capacity. They also have thick walls to withstand the pressure of hydro static pressure which facilitates movement.
Organic Compounds produced at Sources are loaded into Sieve cells. Either through interconnecting Plasmodesmata, or through the membrane proteins of companion cells.
-
Apoplastic Loading
is a method of active transport, and requires ATP. Hydrogen ions are actively transported out of the cell, which causes a gradient of H+ ions to build up outside, and this causes Hydrogen ions to passively diffuse back inside but with a co-transport protein, which requires sucrose movement.
Sucrose diffuses into the water at the source, causing the mixture to become hypertonic, causing water to be drawn from the xylem via osmosis, and this build up of water causes hydrostatic pressure to increase which makes the sap solution move towards of lower pressure which are the sinks.
-
Xylem Transport
Transpiration: The movement of water through the plants and the evaporation through it's aerial parts such as leaves, stems, and flowers.
Plants transport water from the roots to replace water lost due to transpiration.
Adhesive property of water causes tension to be induced in cell walls, Cohesive property of water allows water to be transported under tension.
-