AOBPreview published online on March 2, 2009
Annals of Botany, doi:10.1093/aob/mcp043
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Diel changes in nitrogen and carbon resource status and use for growth in young plants of tomato (Solanum lycopersicum)
INRA, UR 1115 Plantes et Systèmes de Culture Horticoles, F-84914 Avignon, France
* For correspondence. E-mail Stephane.Adamowicz{at}avignon.inra.fr
Received: 8 August 2008 Returned for revision: 10 November 2008 Accepted: 14 January 2009
Background and Aims: Modellers often define growth as the development of plant structures from endogenous resources, thus making a distinction between structural (WS) and total (W) dry biomass, the latter being the sum of WS and the weight of storage compounds. In this study, short-term C and N reserves were characterized experimentally (forms, organ distribution, time changes) in relation to light and nutrition signals, and organ structural growth in response to reserve levels was evaluated.
Methods: Tomato plants (Solanum lycopersicum) were grown hydroponically in a growth room with a 12-h photoperiod and an adequate supply of NO3– (3 mol m–3). Three experiments were carried out 18 d after sowing: [NO3–] was either maintained at 3 mol m–3, changed to 0·02 mol m–3 or to 0 mol m–3. Plants were sampled periodically throughout the light/dark cycles over 24–48 h. Organ WS was calculated from W together with the amount of different compounds that act as C and N resources, i.e. non-structural carbohydrates and carboxylates, nitrate and free amino acids.
Key Results: With adequate nutrition, carbohydrates accumulated in leaves during light periods, when photosynthesis exceeded growth needs, but decreased at night when these sugars are the main source of C for growth. At the end of the night, carbohydrates were still high enough to fuel full-rate growth, as WS increased at a near constant rate throughout the light/dark cycle. When nitrate levels were restricted, C reserves increased, but [NO3–] decreased progressively in stems, which contain most of the plant N reserves, and rapidly in leaves and roots. This resulted in a rapid restriction of structural growth.
Conclusions: Periodic darkness did not restrict growth because sufficient carbohydrate reserves accumulated during the light period. Structural growth, however, was very responsive to NO3– nutrition, because N reserves were mostly located in stems, which have limited nitrate reduction capacity.
Key words: Solanum lycopersicum, tomato, nitrogen, carbon, structural growth, reserves, nitrate, amino acids, carbohydrate, carboxylate