“…Development can last from a few days to a few weeks in herbaceous annual and perennial plants (Pacini and Sarfatti, 1978; Alves Rodrigues et al, 2018), and up to several months in some woody gymno- and angiosperm plants (Chesnoy, 1987; Ferranti et al, 1996). Pollen development can pause at the pollen mother cell stage in some tree species ( Pseudotsuga menziesii , Abies pinsapo , Arbutus unedo ) (Singh et al, 1983; Chiarucci et al, 1993; Arista and Talavera, 1994), at the microspore stage ( Betula verrucosa , Rhododendron species) (Dunbar and Rowley, 1984; Mirgorodskaya et al, 2015), or at the bi-cellular stage ( Corylus avellana ) (Frenguelli et al, 1997). A decrease in pollen volume (12%) and a change in shape (spherical to oval) has been described in Corylus (Frenguelli et al, 1997).…”