Winter Heat Requirements for Tomatoes

Hanna Y. Hanna, Koske, Thomas J., Kuehny, Jeff S.  |  4/19/2005 11:05:16 PM

Heat is needed for proper development.

Energy costs have become an increasingly important issue in production of greenhouse tomatoes. Before lowering greenhouse temperatures to save on fuel bills, consider the effects of low temperature on tomato production.

Dr. Don Ort of the USDA Ag Research Service in Urbana, Ill., found that some crops like tomatoes, soybeans and corn grow and develop less when night temperatures are 50 F and lower. Previous research has found that tomato water relations are abnormal below 57F, but this is different. The research by Dr. Ort indicates that temperatures of 50 F or or lower disrupt the tomato's circadian (daily) clock. This disruption reduces that amount of photosynthate by-products that end up as carbohydrate. 

Research found two key enzymes that are especially affected by low temperatures: sucrose phosphate synthase and nitrate reductase. These enzymes help regulate the activity of the circadian rhythm through regulation of the phosphoprotein phosphotase enzyme. This reduction of enzyme activity lowers the amount of photosynthates produced and thus the growth, yield and sugar content of the tomato.

Those trying to grow tomatoes late in the season or through the winter should provide enough heat to prevent the disruption of this process. Ideal greenhouse tomato minimum temperatures are 62-64 F. You should never allow the house temperature to drop below 60 F if possible.

Always have a source of clean, non-polluting heat or it may have adverse growth effects on the plants and flowering. Symptoms of air contamination from poorly combusted fuel are strap-like and/or curled development of new leaves and blossom abortion (lack of fruit set not caused by low light levels).

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