Evaluation of the effect of clinostat rotation on pollen germination and tube development as a tool for selection of plants in Space

The choice of species and cultivar on which rely to sustain Close Loop Environmental Systems is generally approached by analysing the behaviour of plants in presence of stress (sporophytic selection). In this paper, we investigated the possibility to conduct the selection among genotypes in Space through the male gametophytic selection. Thus, we studied the effect of simulated microgravity on pollen germination and tube development of both woody and herbaceous crop species: Prunus armeniaca (apricot), P. dulcis (almond), Malus domestica (apple) and Vicia faba (broad bean).Pollen collected from just bloomed flowers was assessed for viability and incubated on the optimal growing medium in petri dishes both on a uni-axial clinostat and stationary in 1g1g. Then, pollen was observed under a light microscope to detect percent germination and growth direction. Histochemical analyses were performed to verify the presence and distribution of storage substances. Moreover, specific stainings and epifluorescent microscopy were applied to count nuclei, follow the migration of sperm cells and investigate the presence, size and morphology of callose plugs.Results showed that simulated microgravity affected pollen tube development. The different response showed by the various species indicates that male-gametophytic selection could be useful for the selection of plants in microgravity.