POLLEN OVULE RATIO, POLLEN SIZE, AND BREEDING SYSTEM IN ASTRAGALUS (FABACEAE) SUBGENUS EPIGLOTTIS - A POLLEN AND SEED ALLOCATION APPROACH

The correlation between pollen/ovule (P/O) ratio and breeding system h as generally been accounted for either on the basis that P/O reflects pollination efficiency, or in terms of the sex allocation theory. The following were assessed for taxa belonging to genus Astragalus subgenu s Epiglottis: 1) Degree of correlation between P/O and the breeding sy stem, measured by means of autofertility; 2) The absence or existence of correlation between P/O and pollen grain size; and 3) The ability o f various theories to account for the results obtained. Results showed a minimal correlation between P/O and autofertility, and between P/O and pollen grain size in the taxa studied. Analysis of these results i n terms of the sex allocation theory enabled this correlation to be ex plained as a function of the variation existing between taxa with resp ect to the resources invested in each pollen grain and in each ovule. The predictive capacity of this theory, which has moreover proven valu able in explaining the structural peculiarities of the androecium in t hese taxa, was also highlighted. The type of self-pollination applicab le was also discussed, as was the phenotypic model of selection of sel f-fertilization considered most plausible for these taxa.