Three broccoli (Brassica oleracea L. Italica group) cultivars (Baccus, Packman, and Southern Comet) were grown for 14, 24, or 34 days at 22/18C (day/night) in a greenhouse. Then plants were moved to growth chambers where temperatures were maintained at 26/22, 30/26, or 34/30C and were grown for 1, 2, or 3 weeks before returning them to the greenhouse. A1 varieties when exposed to high temperatures developed smaller heads Packman when exposed to high temperatures resulted in a reduction in uniformity. Other cultivars were not effected. Lack of openness, an important marketable characteristic was reduced by high temperatures. However, Baccus at 34 days old was not effected by the heat. We would expect this response since this is the head development stage and cultivar is heat tolerant. Plant exposed to high temperatures developed heads earlier when held for 3 weeks. When plants were held at 36/30C for 3 weeks, the largest reduction in plant growth was recorded. However, all plants showed a reduction in growth when exposed to high temperatures.
Air-Turbulence and Temperature Gradients Reduced in Plant Growth Chambers by Small-Hole Diffuser Walls