Transport over longer distances in plants proceeds through the vascular system (the xylem and the phloem) and is called translocation.
MEANS OF TRANSPORT
- Diffusion
- Facilitated diffusion
- Passive symports and antiports
- Active transport
OSMOSIS
Osmosis is a special type of diffusion of water across a semi-permeable membrane which depends on pressure gradient and concentration gradient.
In higher plants, there is a vascular system, xylem and phloem, responsible for translocation. Water, minerals and food cannot be moved within the body of a plant by diffusion alone. They are, therefore, transported by a special type of diffusion called imbibition. Water absorbed by root hairs moves deeper into the root by two distinct pathways, i.e., apoplast and symplast.
Transpiration pull is the most acceptable way to explain the transport of water. Transpiration is the loss of water in the form of vapours from the plant parts through stomata.
Phloem is also responsible for transport of food, mainly sucrose, from the source to the sink. The translocation in phloem is bi-directional.