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Carob is a valuable leguminous species for its productions but also for forestation of arid and degraded areas threatened by soil erosion and desertification processes. However, large-scale cultivation of this species is hampered by the difficult propagation by cuttings or seeds. Researches to evaluate genotype tolerance to saline and drought stress during germination and first plant establishment, are also inhibited by the scarce seed germination. In this study, carob seeds, from wild and domesticated carob genotypes collected in a representative area of the Mediterranean basin (Sicily, Italy), were subjected to germination tests under isotonic solutions of polyethylene glycol (PEG) and sodium chloride (NaCl) at −0.5, −1.0, −1.5 MPa. Before germination tests, a 20 min pre-treatment with 96% sulphuric acid was necessary to overcome seed coat dormancy which does not permit germination. Differences in drought and salinity tolerance were determined in the different genotypes during germination. All genotypes exhibited a higher sensitivity to drought stress as compared to salinity stress. The observed differences in some genetically inherited germination characteristics (i.e. base Ψb(50)s and hydrotimes) suggest genetic differences even in seeds of individual old trees situated in close areas, as previously found in other countries of the Mediterranean basin. A greater sensitivity to stress was determined during early radicle growth, an essential feature for early plant establishment in marginal dry areas. In this paper, a protocol to test germination under simulated stress conditions (drought and salinity stress) was established. Including in the analysis other parameters representative of early embryo growth (i.e. radicle elongation), this protocol may be useful to select genotypes for breeding programs towards the selection of tolerant cultivars or rootstocks. It may be also applied to other leguminous species with a difficult germination. [ABSTRACT FROM AUTHOR]

The agronomic use of olive mill wastewaters (OMWs) is limited by some constraints, such as high salinity, acidity, and phenolic compounds that exert phytotoxic and antimicrobial effects. Many researches have been focused on OMW polyphenol effects on germination, but only few on the combined effects of salinity and acidity. In this paper, on Lolium multiflorum Lam., the effects on germination of pH and osmotic potentials similar or higher to those found in OMWs have been investigated. The studied salinity and pH levels did not affect final germination of L. multiflorum , but in some cultivars they significantly enhanced T 50 and consequently reduced initial root growth. Thus, in this species moderately tolerant to salinity, the reduction of germination determined by OMWs cannot be attributed to the osmotic stress and/or to the low pH, but mainly to polyphenols. This research emphasizes the possibility of obtaining good crop establishments after spreading OMWs on soil, choosing herbaceous species tolerant to salinity once polyphenols have been inactivated. [ABSTRACT FROM AUTHOR]

Abstract: The effects of reduced water potential (ψ) in NaCl and pre-osmopriming in PEG, on seed germination and early radicle growth at different temperatures were assessed in the laboratory for sweet sorghum [Sorghum bicolor (L.) Moench] cv. Roce. Five salt solutions (with a ψ of 0-control, −0.22, −0.42, −0.82 or −1.23MPa) and four temperatures of 10, 15, 25 or 35°C were used for germination tests. Daily and final germination, seed moisture at 4 and 24h of imbibition and radicle length 2 days after initial germination were recorded. Sorghum seeds seem to be more tolerant to reduced ψ at optimum temperature. Indeed, at 25°C, down to −0.82MPa seed germination was not affected. The increase in incubation temperature to 35°C determined a greater seed water content and a faster germination than at 25°C at all ψ s, despite the lower final germination percentage. With the lowering of temperature to 15°C, germination percentage significantly declined with the decrease of ψ and at −0.82MPa it reduced to less than 50%. At 10°C seeds failed to germinate at ψ <−0.22MPa due to combined depressive effects of reduced ψ and low temperature. Seed priming enhanced germination and shortened the delay in germination time due to the increase in saline stress, at suboptimal temperatures only. This effect could be explained by the faster water absorption occurring in primed seeds as compared to those unprimed, at these temperatures, regardless of salt concentration of the solution. Root growth was more sensitive than germination to salt stress. Indeed, the increase in NaCl concentration adversely affected root elongation at all temperatures. The beneficial effects of PEG-osmopriming were evident on root growth at all temperatures except the optimal one. From a practical point of view, when early sowings of sweet sorghum are requested, the use of primed seeds is suggested, as PEG-osmopriming is helpful in overcoming the negative effect imposed by reduced water potential upon seed germination under suboptimal thermal conditions. When saline water is available for irrigation at sowing, it may be useful to sow when optimal or nearly optimal temperature may be encountered in the soil in order to avoid the combined stress of temperature and salinity. [Copyright &y& Elsevier]