- Systems with aggregate-like expanded shale, pea gravel or sand provide root support for top-heavy plants. This prevents large plants from dislodging or shifting and incurring injury. Aeroponic and nutrient film systems do not use aggregate, and they rely on the plants resting on mesh or the outer edges of a circle cut into the surface that separates the roots and nutrient solution from the top of the plant. Sometimes nonaggregate systems use Rockwool to anchor the roots near the crown, allowing the remainder of the roots to dangle beneath it.
- The roots in a hydroponic system need abundant contact with nutrient solution to stay moisturized and absorb water and nutrients for growth. Aeroponic systems spray the roots with solution either constantly or at timed intervals. Nutrient film systems allow nutrient solution to slide over the roots at regular intervals. Aggregate systems ensure that nutrient solution remains in close contact with the roots long enough to be absorbed. The aeration method keeps roots immersed in nutrient solution.
- The inverse necessity to saturation is aeration. Plant roots need oxygen to survive. The aeration method uses air pumps to bubble oxygen around the roots suspended in solution so that they do not drown. Most aggregate systems and the nutrient film systems use variations of a flood and drain method to give the roots a chance to "breathe" before they are flooded with solution again. Aeroponics depends on timing and the fact that air is the predominant atmosphere surrounding the roots.
- Ninety percent of the world's plants can form a symbiotic relationship with a fungus called mycorrhiza. This microscopic fungus attaches to plant roots, protects them and breaks down and transports nutrients to the root system. In some aggregate and aeration method hydroponic systems, mycorrhiza may be added to enhance root function and defend roots from root rot and other diseases.
- If the plant roots have gone from white to off-white or brown, they may be dying off. Make sure they're receiving plentiful oxygen, as drowning is a common problem in hydroponic systems. Roots should never be dry to the touch. Check your system regularly for clogs, mechanical failure or improper timing to make sure that nutrient solution reaches the roots at the correct intervals for that species. Always ensure that roots are kept at optimal temperature for nutrient uptake without encouraging disease.
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