Effects of salinity on pollen germination in wild and cultivated leguminous species

Plant sexual reproduction plays a crucial role in species persistence, land colonisation, and the enhancement of genetic diversity. Sexual reproduction in plants encompasses several key processes, including gametogenesis, fertilisation, zygote development, and fruit production. Environmental stresses can affect each of these processes, with male gametogenesis, pollen germination and tube elongation showing special vulnerability. We investigated the effects of salinity on pollen fitness across several species of Fabaceae, a large family which includes economically important crops. We first assessed the in vitro germination capacity of pollen from 14 different species and identified four distinct response patterns to salinity stress. A more detailed analysis was conducted on pollen germination and tube elongation in Medicago marina (dune habitats), Spartium junceum (Mediterranean scrub), and Cicer arietinum (cultivated). For C. arietinum, a positive correlation was observed between pollen germination and tube length, whereas no such correlation was found in the wild species. Furthermore, we examined the fitness of pollen produced by plants of Medicago marina, Lotus creticus, and Ononis ramosissima subjected to salt stress under greenhouse conditions. These species exhibited varying degrees of salt sensitivity, although the three are characteristic of dune habitats. In conclusion, our study reveals that pollen from different species within the Fabaceae family exhibits distinct responses to salinity stress, with variations in salt sensitivity amongst species. These findings contribute to a deeper understanding of how environmental stressors, particularly salinity, affect pollen fitness in plants adapted to different environments.