what is facilitated diffusion in plant cells? explain with the help of a diagram

Diffusion is defined as the net motion of a substance from an area of high concentration to an area of low concentration, 'down a concentration gradient'.

Factors which affect diffusion;

    How steep the concentration gradient is. Concentration gradient is the ratio of molecules on one side of the membrane to the other, many on one side compared to few on the other will result in a faster net rate of diffusion
    Temperature. High temperatures increase the kinetic energy of molecules and ions and thus they move around faster - net rate of diffusion goes up.
    Surface area. A large surface area increases the amount of ions or molecules that can cross at one time, increasing the net rate of diffusion.
    Type of molecule. Large molecules are slower to diffuse, non-polar molecules diffuse more easily through cell membranes as they are soluble.

Molecules and ions that are small enough can cross membranes easily, regardless of polarity, but large polar molecules such as glucose cannot diffuse through a cell membrane. They can only pass through hydrophilic protein channels - this process is known as facilitated diffusion. All the factors that affect diffusion affect facilitated diffusion, and an additional one - how many transport proteins are available.