Nitrogen concentration and photosynthetic photon flux in greenhouse tomato production: I. growth and development
1989
Larouche, R. | Gosselin, A. | Vezina, L.P.
Tomato plants (Lycopersicon esculentum Mill. cv. Vedettos) were grown in growth chambers under two photosynthetic photon flux (PPF; 125 and 250 micromole per s-1 per m-2, high-pressure sodium lamps) conditions for 18 hr and four N fertilization regimes (5, 10, and 20 meq.liter-1) to characterize the ratio of vegetative to reproductive growth. At the lower PPF, vegetative growth was limited and did not respond to N increments in the nutrient solution. At 125 micromole per s- 1 per m-2, maximum yields were obtained at the lowest N fertilization level. At 250 micromole per s-1 per m-2, maximum leaf dry weight and yields were obtained at intermediate N fertilization levels (10 and 15 meq.liter-1). Light levels did not alter the nitrae content of stem sap (but high PPF resulted in nitrate accumulation in leaves) but, at low PPF, nitrate accumulated in leaves at 20 meq N/liter. Nitrate in stem sap varied only slightly with N increments in the nutrient solution. The ratio of fruit fresh weight to leaf fresh weight decreased as N increased in the nutrient solution.
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