the need for plant transport 1.3.1

• diffusion is the net movement of particles of a gas or solute from an area of high concentration to an area of low concentration, down a concentration gradient
• diffusion is a passive process so no energy is required
• diffusion sometimes may require a transport protein to allow a substance to cross a membrane
• shorter distances make diffusion quicker
• bigger concentration differences makes diffusion quicker
• temperature increase causes a rate of diffusion increase
• larger surface area increases rate of diffusion (more transport proteins)
• factors increasing rate of diffusion include: higher temperature, larger difference in concentration, larger surface area, shorter diffusion distance
• factors decreasing the rate of diffusion include lower temperature, smaller difference in concentration, smaller surface area, longer diffusion distance
• surface area to volume ratio is how many times larger or smaller the surface area is compared to the volume
• as the object gets larger, the surface area to volume ratio gets smaller
• surface area to volume ratio is relevant to plant transport because it affects the rate of diffusion
• diffusion is sufficient for single celled algae because they have a high surface area to volume ratio so the rate of diffusion would have sufficient speed, but for a larger organism, the surface area to volume ratio is low and therefore diffusion is too slow
• around a tree, water, mineral ions and glucose are transported
• large plants require a transport system because water and mineral ions are absorbed in the roots, but need to be transported to the leaves for photosynthesis
• large plants need a transport system because sugars are made during photosynthesis in the leaves, but are used in the rest of the plant for either respiration(for energy) or for storing as starch
• evaporation of water from leaves also keeps the plant cool