plant structures and their functions

• photosynthetic organisms are the main producers of food and therefore biomass
• photosynthesis is an endothermic reaction
• photosynthesis equation


  carbon dioxide + water = oxygen + glucose
• thin upper epidermis allows light to penetrate through cells quickly

  rapid gas exchange
• stomata allows Carbon dioxide to diffuse in and oxygen to diffuse out the leaf
• air spaces allow gas exchange of oxygen and carbon dioxide into and out of the cell
• no chloroplasts in the upper epidermis allows all light to pass directly to the palisade mesophyll cells
• the large surface area of the leaf allows an increased area for photosynthesis, light absorption and carbon dioxide absorbtion
• chloroplasts absorb energy from light
• xylem supplies water to cells, some of which is used in photosynthesis
• phloem takes away sucrose and transports it to other cells in the plant
• the leaf being supported by the stem and petiole provides structure to absorb more light
• the palisade mesophyll cells being arranged upright allows more room for more palisade mesophyll cells and minimises the number of cell walls which light must pass through
• a stomata has chloroplasts, a cell wall, a vacuole and a nucleus
• each pore of a stomata is surrounded by a guard cell, which can open and close the stomata
• water makes the guard cell swell to open the stomata
• magnification equation is I=a x m
• soil water enters the root hair cell by osmosis
• root hair cells are adapted to absorb water and mineral ions as they are elongated to have a larger surface area for more water and mineral ions, they have a thin cell wall to absorb water, and lots of mitochondria for active transport
• in plants, glucose can be converted into starch and stored in the cytoplasm, it can be used to synthesise cellulose which is found in plant cell walls, it can be converted into sucrose and transported throughout the plant via the phloem, it can also be used for respiration, to release energy, from glucose, the plant can make protein and lipids
• inverse square law


  light intensity is proportional to 1 over distance squared
• calculation for working out light intensity when no light probe is available

  light intensity (new) = light intensity (original) x distance squared (original) over distance squared (new)
• the limiting factors of photosynthesis are light intensity, carbon dioxide concentration and temperature
• xylem transports water and solutes from the roots to the leaves
• phloem transports food from the leaves to the rest of the plant
• xylem vessels form a continuous tube from roots to leaves, water molecules are joined together due to hydrogen bonds, on reaching the leaves, water moves out of xylem to surrounding cells by osmosis, in air spaces, water evaporates into water vapour and water vapour leaves stomata by diffusion, loss of water in leaves causes low pressure and the roots maintain the high pressure
• lignin in the xylem strengthens the vessels, waterproofing the xylem to prevent water loss
• the xylem cells being dead reduces friction
• the pores in the xylem walls allows water to move sideways into another vessel If there Is a blockage
• no end walls creates a continuous tube to move through by transpiration
• water in the xylem travels one way
• transpiration is loss of water vapour from the surface of leaves
• phosphates are used by plants for dna and cell membrane
• nitrates are used by the plant for dna and amino acids
• magnesium is used by plants for chloroplasts
• cohesion is water to water bond
• adhesion is water to xylem bond
• factors affecting transpiration rate?

  air temperature that is high

  humidity that is lower

  increase in air flow

  leaf size that is larger

  more and bigger stomata

  transpiration stops when stomata closes

  more leaves = greater surface area

  quicker uptake of water in roots
• translocation is the movement of sucrose from leaves to going tissues, storage tissues and developing seed
• transpiration occurs up and down