Sexual reproduction in Eichhornia crassipes (water hyacinth). I. Fertility of clones from diverse regions.
Sexual reproduction in 9 clones of Eichhornia crassipes from different parts of the world was examined in the glasshouse. Eight of the clones flowered regularly throughout the study period while a single clone from Guyana failed to flower. All flowers were mid-styled and produced dimorphic pollen of high viability. Pollination success was markedly affected by temps. below 20 deg C. Seed production was significantly lower when pollination was carried out 24 h after flower-opening compared with pollination 2 h after flower-opening. In a controlled pollination programme, all clones exhibited a high level of seed fertility. Of 2546 flowers pollinated, 94.7% produced capsules with an average of 143.3 seeds per capsule. There were no significant differences in seed-set between self- and cross-pollinations of clones from Louisiana, Florida, Mexico and southern Brazil. Seed-set was significantly higher in cross-pollinations than self-pollinations in clones from California, Sudan, Zaire and Calcutta. Comparisons of the growth and reproductive performance of off-spring obtained from self- and cross-pollinations failed to detect any significant expression of inbreeding depression. Although clonal propagation is the most widespread mode of reproduction in E. crassipes, the genetic potential for sexual reproduction is probably still present in the majority of populations.