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Chabchoub M.A.,Agronomic National Institute of Tunisia | Aounallah M.K.,Agronomic National Institute of Tunisia | Sahli A.,Agronomic National Institute of Tunisia
Acta Horticulturae | Year: 2010

Under Mediterranean condition, the lack of chilling constitutes a limiting factor for deciduous fruit production. To induce dormancy breaking; several chemicals were used by growers but their application effect depend on the spraying time. This work evaluated the consequence of a late application of hydrogen cyanamid on flowering, bud abortion and fruit growth of two pear cultivars, under the climate condition of Tunisia. The experiments were conducted on 'Dr Jules Guyot' and 'Santa Maria' cultivars, known for their middle chilling requirements. The chemicals tested were Dormex applied at 1 and 2%. The control trees were spayed with water. The parameters evaluated were: flowering, bud abortion and fruit growth. Cyanamid treated trees showed varying degrees of advanced and grouped bud breaking in comparison with the control trees. Very satisfactory improvement in synchronization of blossoming was also observed which can increase the chances of effective cross-pollination inducing a positive effect on yield potential.


Boussadia O.,Institute of the Olive Tree station of Sousse | Steppe K.,Ghent University | Zgallai H.,Bayer BioScience N.V. | El Hadj S.B.,Agronomic National Institute of Tunisia | And 3 more authors.
Photosynthetica | Year: 2011

For Tunisian olive tree orchards, nitrogen deficiency is an important nutritional problem, in addition to the availability of water. Establishment of relationships between nutrients such as nitrogen and ecophysiological parameters is a promising method to manage fertilisation at orchard level. Therefore, a nitrogen stress experiment with one-year-old olive trees (Olea europaea L. 'Koroneiki' and 'Meski') was conducted with trees respectively subjected to four nitrogen supply regimes (23.96 meq l-1, 9.58 meq l-1, 4.79 meq l-1 and 0 meq l-1 NO3 -1). The current paper focuses on the use of the SPAD-502 portable chlorophyll (Chl) meter, a nondestructive method for fertilisation management under nitrogen stress conditions of olive trees. Maximum net photosynthetic assimilation rates, chlorophyll fluorescence parameters and the SPAD Chl index were therefore measured simultaneously and the Chl and nitrogen content of the leaves were analysed. Significant correlations were established in the olive tree leaves between SPAD-502 readings on the one hand and Chl content, nitrogen content, photosynthetic assimilation rate, and Chl fluorescence parameters (ΦPSII and ETR) on the other hand. © 2011 Springer Science+Business Media B.V.


Boussadia O.,Institute of the Olive Tree Station of Sousse | Steppe K.,Ghent University | Zgallai H.,Bayer BioScience N.V. Nazarethsesteenweg 77 | Ben El Hadj S.,Agronomic National Institute of Tunisia | And 3 more authors.
Scientia Horticulturae | Year: 2010

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. © 2009 Elsevier B.V. All rights reserved.

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