Promotion of tea pollen tube growth by incubated solution of rapeseed cakes

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Abstract
The existence of growth promoters in rapeseed cakes (an organic fertilizer) was tested by measuring tube elongation in pollen culture in vitro. Growth of tea pollen tubes on an agar medium containing sucrose and boron was strikingly promoted by adding the solution obtained from incubated rapeseed cakes to the medium. Addition of a solution diluted to 1/300 stregnth to the agar medium increased the pollen tube elongation to 153–170% of the control. Maximum activity was found with the solution in which rapeseed cakes had been incubated at 30°C for 2 weeks. The promotive substances were not soluble in ethyl ether, ethyl acetate or n-butanol, but were soluble in water, and diffused out by dialysing against distilled water. These substances were found to be soluble in 50% methanol, and were separated into three fractions by Sephadex G-25 gel filtration. The promotive substances were different from several known growth regulators, amino acids and mineral nutrients.