INFLUENCE OF ROOT TEMPERATURE ON TOMATO GROWTH AND NITROGEN NUTRITION
The tomato reacts strongly to the change in root temperature : at 12°C, plant dry weight and water uptake are less than 70 p. cent of that observed at 22°C.
The poor growth at 12°C is accompanied by a modification of plant nitrogen nutrition. At 12°C, the organic nitrogen and nitrate accumulate in the root, while at 22°C they accumulate in the stem and the petiole. Concurrently the nitrate reductase activity (NAR) in the roots growing at 12°C is always more important than those growing at 22°C. The NAR is more important in the blades and the difference between treatments are low. But the small growth observed at 12°C induces a reduction of total NAR of blades and emphazizes the further growth restriction.