Interactions between Air and Root Temperatures on Greenhouse Tomato: I. Growth, Development, and Yield

Greenhouse tomato plants ( Lycopersicon esculentum Mill. cv. Vendor) were grown at 5 root temperatures (12°, 18°, 24°, 30°, and 36°C) and 4 night air temperatures (12°, 15°, 18°, and 21°) for 3 months. Low root and low night air temperatures contributed to high root dry weight. However, under warm soil temperature conditions (30° and 36°), roots were most efficient in sustaining shoot growth and in absorbing water as indicated by the percentage of shoot dry weight. Shoot growth was maximum at 15° night air temperature and 30° root temperature. High root temperatures are required at low night air temperature for maximum shoot growth. Maximum yields were obtained at a combination of 18° night air temperature and 24° root temperature. An increase in soil temperature partly offsets the detrimental effects of low night air temperatures.