Hydroponic plants are those that grow indoors without soil. If hydroponic tomatoes are planted and fed properly, they can produce just as well -- if not more -- than soil-based plants. Hydroponic plants are still prone to plant diseases and problems.
Chlorosis, or the absence of chlorophyll, is a condition that causes leaves on a hydroponic tomato plant to turn yellow. There are many different causes: poor drainage, injured or compressed roots and nutrient imbalance. The solution depends on which problem is causing leaves to yellow.
Nutrient imbalance in hydroponic tomato plant food causes leaves to turn yellow. Boron toxicity causes leaf tips to yellow. Calcium deficiency causes the upper leaves to yellow while the lower ones remain green. Magnesium and nitrogen deficiency also lead to yellowing of the leaves.
Late blight is a mould disease that causes leaves on a hydroponic tomato plant to turn yellow. This disease spreads by mould spores moving from an infected plant to a healthy one. In the beginning of the infection, either the leaf edges or the centre turns yellow. It is best treated by a dry and sunny climate or copper fungicides.