The most critical phase in plant life is seed germination, which is influenced by environmental factors. Drought and salinity are key environmental factors that affect seed germination. Reduction or alterations of germination when seeds are exposed to these factors have been shown to be due to either the adverse effects of water limitation and/or specific ion toxicity on metabolism. Phytohormones are chemical messengers produced within the plant that control its growth and development in response to environmental cues; small fluctuations of phytohormone levels alter the cellular dynamics and, hence, play a central role in regulating plant growth responses to these environmental factors. To integrate current knowledge, the present review focuses on the involvement of endogenous phytohormones in plant adaptative responses to drought and salinity at one of the plant's developmental phases.

Seed germination is vital for persistence in species that rely on seeds for post-disturbance regeneration. It is a high-risk phase and vulnerable to environmental parameters. Here, I assessed temperature sensitivity for germination in Banksia L.f. (Proteaceae) from south-western Australia, screening all 38 endemic obligate seeder species. A bi-directional temperature gradient plate with 49 temperature combinations (constant and fluctuating) between 5 and 40°C was used to profile germination temperature requirements and identify upper and lower temperature thresholds for germination. Using these data the impact of increasing temperatures on germination in these species was modelled under high and low greenhouse gas scenarios for 2050 and 2070. The results suggest that many Banksia species from the region have wide physiological tolerance for high germination temperatures, although a number of common, but geographically restricted species, such as B. praemorsa, B. oreophila and B. quercifolia, have more narrow temperature windows for germination than at least one of the rarer species (B. verticillata). Only B. dryandroides is expected to decline in germination in the future; however, the optimal germination timing for many species is predicted to occur later under climate warming. In conjunction with declining rainfall, this germination delay will place seedlings closer to the summer dry in this seasonal Mediterranean-climate ecosystem and thus they will be more vulnerable to desiccation. The framework developed here can be used to identify vulnerable species for monitoring of early population decline.

Light and fluctuating temperatures are two important factors triggering seed germination. The aim of this work was to: (1) elucidate the effect of temperature, light regime and storage time on seed germination in nine taxa of Verbascum spp., collected from different habitats in the Mediterranean area; and (2) estimate threshold temperatures for seed germination. For all taxa, germination assays were performed at constant and fluctuating temperatures, both in continuous darkness (D) and in alternating light/dark (L/D; 12 h photoperiod). Final germinated proportions (FGPs), base (Tb), optimal (To) and cut-off (Tc) temperatures were derived. At constant temperatures, seed germination was strongly suppressed under the D regime. In L/D, the effect of storage time was very small and the highest FGPs were observed from 15 to 30°C (40–100%), depending on the species. Tb ranged from below 7 to above 10°C and it appeared to be constant within each seed lot. To and Tc showed some within-lot variability and were higher for fast-germinating seeds in each lot. Considering fluctuating temperatures, germination appeared to be quicker and more complete than at constant temperatures. The germination of Verbascum spp. is favoured in L/D and fluctuating temperatures, which explains their pioneer character when positioned near the soil surface and under a low vegetation canopy. V. arcturus and V. pinnatifidum were shown to be less favoured by L and fluctuating temperatures, which might explain their ability to germinate in rocky areas or sandy dunes, even when they are not directly exposed to the light.

Swartzia langsdorffii seeds have recalcitrant characteristics. Nonetheless, dispersal begins in the month with the lowest precipitation in the studied region, which could lead to seed death by desiccation. Therefore, the objectives of this study were: (1) to characterize the physiological behaviour of S. langsdorffii seeds related to their desiccation sensitivity/tolerance; and (2) to assess the morphophysiological characteristics that enable the seeds to remain viable after dispersal. Fruits and seeds were subjected to biometric evaluation and the anatomical and ultrastructural features of the seeds were determined. Field assessments were performed to determine the capacity of the seeds to maintain viability and to verify the relation between seed viability, diaspore water content and environmental variables. Seeds of this species were found to be recalcitrant and showed pores distributed throughout the seed coat, and contained a large number of stomata in the hypocotyl–radicle axis epidermis. Moreover, phenolic compounds were found throughout the radicle region. Seeds remained viable in the soil for up to 7 months after dispersal without a significant decrease in water content, despite the low precipitation and soil water content. Radicle protrusion began 5 months after dispersal and coincided with partial fruit decomposition at the beginning of the rainy season. Thus, the possible microclimate created by the pericarp, with the moisture content of the aril and the soil, the presence of the structures in the axis, such as the pores and stomata, the chemical composition and the morphology of S. langsdorffii seeds could favour maintenance of their viability until the beginning of the rainy season.

New trends in crop breeding include analytical approaches to identify metabolic fingerprints that can be used for associations to the genetic background. The biochemical phenotype, as a result of plant endogenous factors and interaction with the environment, has the potential to increase the accuracy of forecasting regarding agronomical quality factors. In this study a metabolite profile analysis by gas chromatography–mass spectrometry (GC–MS) was conducted on sets of seed material from sugar beet. One set represented high-performing varieties with a close genetic background and with a similar quality in terms of germination capacity. The second set contained seed lots from different genotypes comprising different germination capacities. By multivariate statistical analyses high variance in both sample sets was revealed. These data were further allocated to corresponding metabolite classes. It could be shown that an untargeted GC–MS approach has the power to resolve differences in the molecular phenotypes of related offspring lines. Metabolic profiles were found to correlate more to genotypic differences than to differences in the germination capacity.

Poor wheat seed quality in temperate regions is often ascribed to wet production environments. We investigated the possible effect of simulated rain during seed development and maturation on seed longevity in wheat (Triticum aestivum L.) cv. Tybalt grown in the field (2008, 2009) or a polythene tunnel house (2010). To mimic rain, the seed crops were wetted from above with the equivalent of 30 mm (2008, 2009) or 25 mm rainfall (2010) at different stages of seed development and maturation (17–58 DAA, days after 50% anthesis), samples were harvested serially, and subsequent air-dry seed longevity estimated. No pre-harvest sprouting occurred. Seed longevity (p50, 50% survival period in experimental hermetic storage at 40°C with c. 15% moisture content) in field-grown controls increased during seed development and maturation, attaining maxima at 37 (2008) or 44 DAA (2009); it declined thereafter. Immediate effects of simulated rain at 17–58 DAA in field studies (2008, 2009) on subsequent seed longevity were negative but small, e.g. a 1–4 d delay in seed quality improvement for treatments early in development, but with no damage detected at final harvests. In rainfall-protected conditions (2010), simulated rain close to harvest maturity (55–56 DAA) reduced longevity immediately and substantially, with greater damage from two sequential days of wetting than one; again, later harvests provided evidence of recovery in subsequent longevity. In the absence of pre-harvest sprouting, the potentially deleterious effects of rainfall to wheat seed crops on subsequent seed longevity may be reversible in full or in part.

Desert plants are exposed to water shortage and often salinity, instantly after dormancy withdrawal. We studied the effects of aridity and salinity on germination and initial growth of Bassiaindica, B. iranica and B. prostrata. We hypothesized that: (1) all species would exhibit adaptations to water shortage immediately after germination, including rapid root growth and high seedling-survival rates; and (2) obligate halophytes benefit from positive effects of salinity on germination success and desiccation tolerance. After we germinated seeds in water or NaCl solutions, desiccated and rehydrated them, we found that all three species showed rapid germination and root elongation, as well as good germination success. However, salinity had a negative effect on the germination success of all three, with only B. indica germinating in 3% NaCl. Salinity had a positive effect on desiccation tolerance of B. indica seedlings, but had no significant effect on either B. prostrata or B. iranica. Thus the presence of salinity immediately after germination can protect halophyte seedlings from desiccation. To the best of our knowledge, survival of seedlings after periods of desiccation and rewetting with solutions of up to 3% NaCl has never been reported. Studying salinity tolerance in halophytes is important in a world exposed to expanding desertification.

Orchid seeds are among the smallest seeds in nature and they are naturally rich in fatty acids. However, the fatty acid composition of orchid seeds has not been investigated because the sample masses utilized for widely used methods for fatty acid profiling would generally require prohibitively large numbers (i.e. 10,000s) of seeds. The present work aimed to develop a method for fatty acid analysis using gas chromatography–mass spectrometry on small quantities (mg) of seeds. The method was developed using the seeds of two species, Dactylorhiza fuchsii, a temperate terrestrial, and Grammatophyllum speciosum, a tropical epiphyte. A range of sample masses was tested to determine the minimum mass required to achieve reliable fatty acid composition data. A direct transesterification method was used, which did not require extraction of fatty acids from seeds prior to analysis, and the effects of seed processing (crushed versus intact seeds) and incubation time in toluene on fatty acid yield were tested. Stable fatty acid profiles were obtained using as little as 10 mg of seeds. Neither crushing the seeds nor extending the toluene incubation step had much effect on the fatty acid yield. The simple direct transesterification method presented will enable the fatty acid composition of orchid seeds, and possibly other small seeds, to be determined reliably for studies into seed development, storage and germination.