Warmth, after a period of low temperature, will break dormancy and plants will resume active growth. High temperatures cause increased respiration sometimes above the rate of photosynthesis. This means that the products of photosynthesis are being used more rapidly than they are being produced. For growth to occur photosynthesis must be greater than respiration. Low temperatures can result in poor growth.
Photosynthesis slows at low temperatures.
Since photosynthesis is slowed, growth is slowed and this results in lower yields. Not all plants grow best in the same temperature range. Florist cyclamen does well under very cool conditions while many bedding plants prefer a higher temperature. Recently it has been found that roses can tolerate much lower nighttime temperatures than was previously believed. This has meant a conservation in energy for greenhouse growers.