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CROP PHYSIOLOGY & METABOLISM

Mineral Nutrition of Tomato under Diurnal Temperature Variation of Root and Shoot

^a Dep. of Forestry and Horticulture, Connecticut Agric. Exp. Stn., New Haven, CT 06504-1106 USA
^b Yale Univ., New Haven, CT 06520 USA

martin.gent{at}po.state.ct.us

Should root and shoot temperature vary in synchrony to optimize nutrient uptake, particularly when there is a large difference in temperature from day to night (DIF) of air and soil? To answer this question, tomato (Lycopersicon esculentum Mill.) seedlings were grown in greenhouses with the air heated to give either a +14°C DIF or a +5°C DIF in air temperature with a 16°C mean. The root medium was either unheated except by the air, or heated to 21°C constantly, only in the day, or only in the night. Experiments were repeated in early March and April in two years. Overall, growth was faster and there were higher concentrations of elements in leaves under +5°C compared with +14°C air DIF. Root-zone heating significantly increased growth and nutrition, compared with no heating. There was a trend in growth and nutrient concentration with timing of root heating: constant > day > night. These differences in growth and nutrition were similar under a +5°C or +14°C air DIF, and they were slight compared with no root-zone heating. For most nutrients, coordination of root and shoot activity related to uptake and metabolism did not require synchronous variation of air and soil temperature. Uptake and transport of nitrate was an exception. Heating roots in the day resulted in the highest nitrate concentration in leaves under a +14°C air DIF, whereas heating constantly was optimal under a +5°C DIF. Our results indicate nitrate metabolism did benefit from synchronous variation in air and root temperature.

Abbreviations: DIF, difference between day and night temperature