Towards a characterisation of the wild legume bitter vetch (Lathyrus linifolius L. (Reichard) Bässler): heteromorphic seed germination, root nodule structure and N-fixing rhizobial symbionts.

Lathyrus linifolius L. (Reichard) Bässler (Fabiaceae, bitter vetch) is a nitrogen (N) fixing species. A coloniser of low nutrient (N) soils, it supports biodiversity such as key moth and butterfly species, and its roots are known for their organoleptic and claimed therapeutic properties. Thus, the species has high potential for restoration, conservation, novel cropping and as a model species. The last because of its genetic synteny with important pulse crops. However, regeneration and functional attributes of L. linifolius remain to be characterised. Seeds of L. linifolius were characterised using physical, colorimetric and chemical data. Ultrastructural and functional characterisation of the N-fixing root nodules included immunolabelling with nifH protein antibodies (recognising the N-fixing enzyme, nitrogenase). Endosymbiotic bacteria were isolated from root nodules and characterised phylogenetically using 16S rRNA, nodA and nodD gene sequences. L. linifolius yielded heteromorphic seed of distinct colour classes: green and brown. Seed morphotypes had similar C:N ratios and were equally germinable (ca. 90%) after scarification at differing optimal temperatures (16 and 20 °C). Brown seeds were larger and comprised a larger proportion of the seed batch (69%). L. linifolius root nodules appeared indeterminate in structure, effective (capable of fixing atmospheric N) and having strains very similar to Rhizobium leguminosarum biovar viciae. The findings and rhizobial isolates have potential application for ecological restoration and horticulture using native seeds. Also, the data and rhizobial resources have potential applications in comparative and functional studies with related and socio-economically important crops such as Pisum, Lens and Vicia.

Seed enhancing treatments: comparative analysis of germination characteristics of 23 key herbaceous species used in European restoration programmes.

The response of seeds from 23 wild plant species to a range of seed enhancing treatments was studied. We tested the hypothesis that sensitivity of the 23 species to these compounds is related to their ecological niche. The three ecological niches considered were open land, open-pioneer and woodland. Hence, the germination of a species is likely adapted to different light conditions and other environmental signals related to the niche. As representatives of environmental signals, the effects of smoke-related compounds (karrikinolide, KAR1 ), nitrate and plant growth regulator (gibberellic acid, GA3 ) on germination were studied. Seeds were exposed to these additives in the imbibition medium; all described as germination cues. We also investigated the effect of light regimes and additives on germination parameters, which included final germination, germination rate and uniformity of germination. Seeds were placed to germinate under three light conditions: constant red light, constant darkness and 12 h white light photoperiod. We observed inhibition by KAR under light in some species, which may have ecological implications. The results showed that no single treatment increased the germination of all the tested species, rather a wide variation of responsiveness of the different species to the three compounds was found. Additionally, no interaction was found between responsiveness to compounds and ecological niche. However, species in the same ecological niche and dormancy class showed a similar responsiveness to light. Species that share a similar environment have similar light requirements for germination, while differences exist among species in their responsiveness to other germination cues.