plant structures and their functions

• during photosynthesis, photosynthetic organisms, such as green plants and algae use energy from the sun to make glucose
• some glucose created is used to make larger, complex molecules that the plants or algae need to grow.
• biomass - the mass of living material in an organism
• photosynthetic organisms are the main producers of food for nearly all life on earth
• photosynthesis happens inside chloroplasts which contain chlorophyll which absorbs light which is transferred to the chloroplasts by light
• photosynthesis equation- carbon dioxide + water->glucose + oxygen (6CO2 +6H2O -> C6H12O6 +6O2)
• photosynthesis is an endothermic reaction as energy is taken in from surroundings
• the rate of photosynthesis is affected by light intensity, the concentration of CO2 and the temperature. these factors can all become the limiting factor (stops photosynthesis from happening any faster)
• light intensity is directly proportional to 1/(distance from lamp)^2
• flowering plants have 2 types of transport vessel- xylem and phloem. both of these go to every part of the plant but they are totally separate
• root hairs take in minerals and water from the soil and transport them to the rest of the plant
• the concentration of mineral ions is usually higher in the root hair cells than in the soil around so the mineral ions are absorbed by active transport but the water is absorbed by osmosis
• phloem tubes transport food
• phloem tubes are made up of columns of elongated living cells with small pores in the end walls to allow stuff to flow through. they transport food substances (mainly sucrose) made in the leaves to the rest of the plant for immediate use (e.g. in growing regions) or for storage
• translocation - the movement of sugars and amino acids from the leaves to the rest of the plant- requires energy from respiration
• xylem tube takes water up
• xylem tubes are made up of dead cells joined end to end with no end walls between them and a hole down the middle. they are strengthened with a material called lignin
• the xylem carries water and mineral ions from the roots to the stem and leaves.
• the movement of water from the roots, through the xylem and out of the leaves is called the transpiration system
• transpiration is caused by the evaporation and diffusion of water from a plant's surface. mostly happens at the leaves
• the loss of water creates a slight shortage of water in the leaf so more water is drawn up from the rest of the plant through the xylem vessels to replace it. this in turn means more water is drawn up from the roots, and so there is a constant transpiration stream of water through the plant.
• the transpiration stream carries mineral ions that are dissolved in water along with it
• stomata are needed for gas exchange
• stomata are tiny pores on the surface of a plant. they are mostly found on the lower surface of leaves. stomata allow CO2 and oxygen to diffuse directly in and out of a leaf. they also allow water vapor to escape during transpiration
• stomata are surrounded by guard cells which change shape to control the size of the pore. when guard cells are turgid, the stomata are open and when the guard cells are flaccid, the stomata are closed.