Effects of nitrogen deficiency on leaf photosynthesis, carbohydrate status and biomass production in two olive cultivars ‘Meski' and ‘Koroneiki'
2010
Boussadia, O. | Steppe, K. | Zgallai, H. | Ben El Hadj, S. | Braham, M. | Lemeur, R. | Van Labeke, M.C.
The effects of nitrogen deficiency on CO₂ assimilation, carbohydrate content and biomass were studied in two olive (Olea europaea L.) cultivars (‘Meski' and ‘Koroneiki'). One-year-old plants were grown in pots and subjected to four nitrogen levels for 58 days. Nitrogen-deficient plants had significant lower leaf nitrogen and chlorophyll a contents. They also showed a significant reduction in their photosynthetic capacity. A tolerance difference between cultivars was observed: ‘Meski' proved to be more efficient in maintaining CO₂ assimilation rates than ‘Koroneiki' under nitrogen deficiency, which was reflected by increased photosynthetic nitrogen use efficiency. Accumulation of carbohydrates, especially starch, mannitol, sucrose and glucose, was observed in nitrogen-deficient leaves. This indicates that both the high carbohydrate and the low nitrogen content inhibit photosynthesis in nitrogen-deprived olive plants. Total biomass was strongly reduced (mainly caused by a decrease in leaf dry weight) under nitrogen deficiency for both cultivars, but root:shoot ratio was hardly affected. Elongation of fine roots was enhanced in ‘Koroneiki' under severe nitrogen-deprivation.
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