A basic understanding of some major plant processes will help hydroponic growers understand why specific problems occur and what changes should be made to prevent them from arising.  Firstly however a basic understanding of some major plant components is required.

Vascular system
This is the plants 'plumbing' system. It is broken into 2 distinct sections.

1)  Phloem is responsible for:

-  Carrying sugar to specific areas in the plant for respiration (i.e. to produce energy) or for storage as starch until required.

-  Carrying starches after dormancy (i.e. in spring) that were stored in roots / stems.

-  Carrying growth regulators and systemic agents.

2)  Xylem is used to carry water, nutrients and oxygen from the roots to the rest of the plant.

Roots

Roots facilitate the uptake of water, oxygen and nutrients.

Root hairs are responsible for the majority of uptake. Root hairs are alive for just a few days and cover about l cm of a roots overall length at any given time.  Root hairs are located close to the growing tip of each root.  Therefore if new root growth is limited then oxygen, water and nutrient uptake will be restricted.

Leaves

'Parenchyma' cells are cells that photosynthesise and are concentrated on the upper surface of the leaf.

'Stomata' are valves concentrated on the lower side of the leaf. Through these pass carbon dioxide (required for photosynthesis), water vapour and oxygen (by-products of photosynthesis), water and carbon dioxide (by-products of respiration), foliar sprays etc.

Within the leaf are vascular structures for carrying water and nutrients to the leaf cells and for taking sugars away.

For the next section in this article:

"Plant processes (photosynthesis, respiration, transpiration)"