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- Nutrient deficiencies in carob (Ceratonia siliqua L.) grown in solution culturePublication . Correia, P. J.; Pestana, M.; Martins-Loução, M. A.The hypothesis was tested that carob (Ceratonia siliqua L.) is able to develop morphological and physiological adaptations to tolerate or at least mitigate soil nutrient deficiencies. In this work we studied the effects of N, P, Mg, Ca and Fe deficiencies on plant morphology, biomass partitioning, concentrations of chlorophyll, fluorescence and root tip ferric chelate-reductase in carob rootstocks grown in hydroponics. Young rootstock trees were grown in hydroponics with half-strength Hoagland's solution (control) or without N, P, Mg, Ca and Fe (treatments N0, P0, Mg0, Ca0 and Fe0). Nitrogen, and P deficiency affected shoot and root growth but not biomass partitioning or photosynthetic efficiency. Plants without Mg had a few large non-ramificated roots and low photosynthetic efficiency, similar to the Fe-starved plants. Root ferric chelate-reductase activity (FC-R) expressed on a fresh weight basis was higher under P and Mg deficiencies compared with control plants, but Fe0 plants had lower FC-R activity if dry weights are used. The response of carob-tree to these particular nutrients depletion may support the ecological plasticity of this species. Under natural conditions, lack of Fe and Mg in the soil is not likely to occur, but if N and P are limiting, carob growth (shoot and root dry weights) may be negatively affected. Even so, photosynthetic efficiency is maintained, and under P stress FC-R activity may increase.
- Effect of nitrogen and potassium fertilisation on vegetative growth and flowering of mature carob trees (Ceratonia siliqua): variations in leaf area index and water use indicesPublication . Correia, P. J.; Martins-Loução, M. A.This work aimed to assess how potassium (K) and nitrogen (N) fertilisation may affect the use of precipitation in terms of vegetative and flowering response of 15-year-old carob trees during a 3-year experiment. A field trial was conducted in 1997, 1998 and 1999 in Algarve (Southern Portugal) in a calcareous soil. Four fertilisation treatments were tested: no fertiliser (control); 0.8 kg N/tree (N treatment); 1 kg K 2 O/tree (K treatment) and 0.8 kg N/tree plus 1 kg K 2 O/tree (NK treatment). No irrigation was applied during the experimental period. Branch length increments were measured every month throughout the growing season and inflorescence number was registered once per year. There was a strong seasonal effect on vegetative growth, since low levels of precipitation (115 mm) during October 1998–March 1999 suppressed the increment in branch length. N supplied to the trees (N and NK treatments) tended to increase water use indices in terms of vegetative growth. No response to K alone was observed in trees fertilised only with K. The number of inflorescences increased throughout the experimental period, particularly for N and NK treatments, and a reduction of the precipitation amount during April, May and June, may also enhance flowering. This knowledge could be important when making decisions concerning fertilisation under dry conditions. The results reported here indicate that tree growth (expressed as the branch growth) and flower production under dry-farming conditions, may be achieved by applying 0.8 kg of N (as ammonium nitrate) per tree during the growing season. However, N uptake and use depends on soil water availability.
- Determination of chemical composition of Anatolian carob pod (Ceratonia siliqua L.): sugars, amino and organic acids, minerals and phenolic compoundsPublication . Ayaz, Faik Ahmet; Torun, Hülya; Ayaz, Sema; Correia, P. J.; Alaiz, Manuel; Sanz, Carlos; Grúz, Jiri; Strnad, MiroslavCarob pod is the fruit of the carob tree (Ceratonia siliqua L. Fabaceae). The fruit and its products, sold both in large stores and local markets, contribute strongly to the diet of people living in the Mediterranean areas of Europe and Turkey. This study reports the composition of carob pods sampled in West and South Anatolia. Sucrose (437.3 mg/g dry weight), glucose (395.8 mg/g dry weight) and fructose (42.3 mg/g dry weight) were the major sugars identified and quantified in the fruit. Total phenolics (13.51 mg gallic acid equivalents [GAE]/g dry weight), proanthocyanidin (0.36 mg GAE/g dry weight), gallotannins (0.41 catechin equivalents [CE]/g dry weight) and flavanols (3.21 mg CE/g dry weight protein) content of the fruit were also determined. Gallic acid (3.27 mg/g dry weight) was the most abundant phenolic acid present in all three phenolic fractions (free, ester and glycoside) isolated from pods. Aspartic acid (18.25 mg/g dry weight protein) was the predominant amino acid in the pod protein fraction. Eight minerals were quantified in the fruit. Among the analyzed major minerals, K (9.70 mg/g dry weight) was the most abundant element present, and the pods were richer in Ca than in P and Mg. Levels of trace minerals were comparable to other plant species. The data are discussed in terms of the nutritional value of the carob pod.
- The root ferric-chelate reductase of Ceratonia siliqua (L.) and Poncirus trifoliata (L.) Raf. responds differently to a low level of ironPublication . Pestana, M.; Gama, Florinda; Saavedra, Teresa; Varennes, Amarilis de; Correia, P. J.Iron (Fe) deficiency is a common nutritional disorder in several crops grown in calcareous soils, but some species are well adapted to these conditions. A hydroponic experiment was conducted to compare the response of a calcicole species Ceratonia siliqua L. (carob) and of Poncirus trifoliata (L.) Raf., a citrus rootstock very sensitive to Fe deficiency. Rootstocks from both species were grown in nutrient solutions without Fe (0 M Fe), with 1 M Fe, and with 10 M Fe (carob) or 40 M Fe (P. trifoliata). A low level of Fe or its absence in the nutrient solution led to a significant decrease in P. trifoliata vegetative growth and in SPAD readings. The root activity of ferric-chelate reductase (FC-R), a key enzyme in Fe uptake, was low in the absence or with high levels of Fe. Its highest values were in roots exposed to a low level of Fe as described in several sensitive species. In contrast, the activity of FC-R was very high in carob in the absence of Fe and was decreased sharply even when only a low level of Fe was present in the nutrient solution. Plant growth and SPAD readings in the leaves of carob were similar in all treatments. Carob seems to maintain a large activity of root FC-R that may ensure enough Fe to satisfy plant demand. The fact that it presents a slow growing pattern may also contribute to the tolerance of this species to low levels of external Fe.
- Effect of N-nutrition and irrigation on carob (Ceratonia siliqua L.) fruit productionPublication . Correia, P. J.; Martins-Loução, M. A.Carob is a traditional crop in Mediterranean areas. It exhibits drought resistance (Lo Gullo and Salleo 1988. Nunes et al. 1989) and tolerates different edaphic conditions (Martins-Loução and Brito de Carvalho 1990).