Pollen-pistil size correlation and pollen size-number trade-off in species of Argentinian Nyctaginaceae with different pollen reserves

Data on pollen and pistil traits from 14 Argentinean Nyctaginaceae species with starch or lipids as pollen reserves are presented. We expect differences in the traits between these two groups of species, but the same pattern within each group for (a) the relationship between pollen size and pistil length assuming that pollen tube length is predetermined by provisions in the pollen independently of the pollen reserve type, and for (b) a trade-off between size and number because available resources for male function are not unlimited. In particular we expect that (a) species with longer pistils will have larger pollen grains, (b) pollen grain size and the number of pollen grains per flower will be negatively correlated. Significant differences in the mean pollen number per flower and mean pollen size were observed between species with different pollen reserve type but not for pistil length. Then, correlation analyses were performed for species with starchy pollen or with pollen with lipids separately. Pollen size - pistil length correlation was positive and significant for species with starchy pollen but not for species with pollen with lipids. On the other hand, pollen size - number correlation was not significant for both starchy and oil-rich species. Results suggest that pollen reserve type would be a relevant factor that constraint pollen size in species of Nyctaginaceae, and that this pollen trait should be considered when studying pollen-pistil relationships, mainly between species of those families with mixed pollen reserves.