Combined effect of temperature and water stress on seed germination of four Leptocereus spp. (Cactaceae) from Cuban dry forests

Abstract

Cactus seeds have developed adaptations to survive with high temperatures and low soil moisture in their habitats. We studied the effect of the combination of four water potentials (0, −0.2, −0.4 and −0.6 MPa) and two temperatures (25°C and 35°C) on germination and seedling mass of four endemic Leptocereus species from Cuba. There were two semi‐arid coast species (L. arboreus and L. santamarinae) and two species inhabiting dry inland karstic hills (L. ekmanii and L. scopulophilus). We hypothesized that: (a) a decrease in water potential and an increase in temperature would result in low and slow germination, as well as in low seedling mass, and (b) ungerminated cactus seeds after exposure to combined water and temperature stress would have a high recovery capacity. The minimum time required for the seeds to start germination (Tmin), mean germination time (MGT) and germinability were evaluated. In addition, seed mass, the recovery after treatments of non‐germinated seeds, and the seedling fresh mass obtained under different treatments were compared between species. In general, germination was only obtained at 25°C and germinability and seedling mass were drastically affected by the reduction from 0 MPa to −0.2 MPa. Seeds showed thermoinhibition at 35°C at all water potentials. There was a tendency to increase the MGT with decreasing water potential in three species. Low seed recovery occurred at all combined treatments for three species. If the predictions of increased temperature and decreased rainfall for the Caribbean region occur, a reduction in the germination of the Leptocereus species studied is expected.

Effect of osmotic stress and salinity on germination and mucilage expansion of seeds of Plantago albicans L. (Plantaginaceae): Inter‐population variation

“…Salinity and osmotic stress influenced germination percentage and velocity in seeds from different populations, as expected (Tables 2 and 3). All populations showed a decrease of their final germination when germinated in PEG or NaCl solutions, as seen in other plant species (Amini et al, 2021; Barrios et al, 2021). P. albicans seems to be a plantain better adapted to salinity and water stress conditions than other species of the genus, as the reduction of germination with similar solutions in P. lanceolata were much higher: from 82% in control seeds to 24%–32% for seeds treated with NaCl or PEG (Mira et al, 2018).…”