Abstract
The carob tree (Ceratonia siliqua L.) is an important component of the Mediterranean vegetation and its cultivation is important environmentally and economically. It is also an interesting leguminous species for afforestation-reforestation. In this study, carob seeds collected in a representative area of the Mediterranean basin at the national park of Gouraya (Béjaïa, Algeria), were subjected to germination tests under Mediterranean seawater (SW) irrigation of different concentrations (0, 10, 30, 50 and 100% SW) for 15-day period. Before germination tests, a 20 min pre-treatment with 96% sulphuric acid was necessary to overcome seed coat dormancy which does not permit germination. Results showed that the seeds of C. siliqua were able to germinate at different seawater concentration, except for 50% SW and 100% SW which resulted in total inhibition of germination. The maximum number of C. siliqua seed germination of 100% FGP (final germination percentage) appeared at 0% SW and 10% SW. Only 35.5% of the seeds have germinated in 30% SW. Ungerminated seeds of C. siliqua from different SW treatments showed medium germination recovery (FGPRecov) of 39.9% at 50% SW and low recovery of 18.2% at 100% SW when transferred to distilled water after 15 day-period. Seedlings length and seedling fresh and dry weight were significantly (P < 0.001) decreased with increasing SW concentrations. Seedling water content remained constant in 10% SW in comparison with the control, while it decreased very slightly in 30% SW. These findings may serve as useful information for C. siliqua habitat establishment and afforestation-reforestation programs in coastal sites and for exploiting seawater in the area.
Highlights
Carob tree is recommended for forestation of arid and degraded areas threatened by soil erosion and desertification (Riva et al 2017) and, due to its ability to preserve and enrich the fertility of the soil
The maximum number of C. siliqua seed germination of 100% Final germination percentage (FGP) appeared at salinity 0% SW and 10% SW, which indicated that these levels of salinity are the suitable germination salinity environment for C. siliqua seeds
We reported for the first time the effects of SW on C. siliqua seed germination and seedling establishment; and our results indicated that SW can significantly influence C. siliqua seed germination and seedling emergence
Summary
Water is one of the most restricting factors for plant growth in arid and semiarid areas, and rainfed agriculture has poor and unpredictable yields (Wani et al 2011). Some studies have investigated carob pods as a substrate for the synthesis of citric acid (Roukas 1999) and as a readily accessible and inexpensive material for bioethanol production (Makris and Kefalas 2004) It is a drought-resistant fruit species that grows well on poor, calcareous, sandy and calcareous soils (Janick and Paull 2008). Carob tree is recommended for forestation of arid and degraded areas threatened by soil erosion and desertification (Riva et al 2017) and, due to its ability to preserve and enrich the fertility of the soil It is useful in the rehabilitation of marginal areas of the Mediterranean basin not adapted to other agricultural uses (Malfa et al 2010; Correia and Pestana 2018). The performance of some germination and growth characteristics including germination kinetics, mean germination time, germination recovery, shoot and root length, seedling fresh and dry weight and seedling water content of the species were investigated
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