Relative importance of sucrose, pH, osmoticum and plant growth regulators on efficiency of pollen tube emergence in Clitoria ternatea L. (butterfly pea) in vitro

Pollen of butterfly pea (Clitoria ternatea L.) could germinate in vitro with emergence of 1, 2 and 3 tubes from individual pollen grain on germination medium (modified after Mercado et al. Sci Hortic 57:273–281, 1994). The highest percentage of pollen germination was observed on medium supplemented with 20% sucrose while addition of osmotica such as polyethylene glycol or mannitol did not have positive effect on butterfly pea pollen germination. Starch utilization, through conversion to simpler sugars including sucrose, may be the cause for pollen tube elongation. The optimum pH for maximum germination (42%) was recorded to be 5.7. Addition of various plant growth regulators including brassin-like substance and GA3 singly into medium supplemented with 20% sucrose at pH 5.7 did not result in germination percentage higher than that on the medium supplemented with only 20% sucrose. The germination percentage was increased to 71% and the pollen tube length was the greatest when butterfly pea pollen was cultured on medium supplemented with 20% sucrose, 0.25 mg L− 1 brassin-like substance and 1 mg L− 1 GA3 at pH 5.7. This suggests that brassin-like substance and GA3 may play an important synergistic role on pollen germination of butterfly pea in vitro.