The Role of Boron, Silicon and Nucleic Bases on Pollen Tube Growth of Lilium longiflorum (L.)

It is possible to obtain pollen germination and pollen tube growth in vitro if boric acid is present. In this work the effect was studied using as a semiquantitative parameter the mean length (J) o f Lilium longißorum pollen tubes. Pollen tube growth was examinated in depend­ ence on boric acid, ortho-silicic acid, nucleic bases, Ca2+ and Zn2+ in 10% sucrose solution. The maximum o f 7is obtained for concentrations between 2 -2 0 ppm boron. The simultaneous supply o f silicon added as water glass leads to a synergistic stimulation effect on pollen tube growth and facilitates branching. The silicon action is preceded o f a pollen tube growth inhibi­ tion period during 3 h. Adenine and guanosine are able to substitute partially boron as pollen germination and pollen tube growth stimulator. Concentrations o f 100 ppm adenine leads to half the boron effect. The same stimulation effect is obtained by guanosine. Ca2+ can partially substitute boron as well. The stimulation action o f boron is significantly attenuated by Zn2+ and by the herbicide Dicuran. These and preceding results from physiological studies indicate that boron and silicon should be essential trace elements for the regulation o f molecular bio­ logical processes.