Effect of benzylaminopurine on fruit set and seed development in pigeonpea ( Cajanus cajan)

Abstract

Terminal racemes of pigeonpea ( Cajanus cajan L.; dwarf, determinate cv. ICPL 85015) were sprayed during early fruit-set with 2, 20, or 200 mg l −1 6-benzylaminopurine (BAP). At harvest (50% dry fruits), treated racemes were longer, with thicker stems and more axillary branches, and had more, larger fruits and leaves than did control racemes. The greatest increase in total dry mass (TDM) occurred with the 20 mg l −1 BAP treatment, but stem and leaf mass increased up to the 200 mg l −1 BAP treatment level. Pericarp mass and seed number per raceme increased with increasing BAP level, as did the number of fruits ≤2 cm long, with unfilled, aborted seeds. Total seed mass (TSM) was greatest with 20 mg l −1 BAP treatment, while at the higher concentrations of BAP, TSM declined to the control level. The ratio of pericarp mass to TSM increased significantly with 20 mg l −1 and 200 mg l −1 BAP treatments. TSM per fruit, mean individual seed mass, seed number per fruit, and the ratio of TSM to TDM decreased as BAP level increased, with no apparent minima attained with 200 mg l −1 BAP. BAP treatment appeared to promote competition for photosynthates between developing seeds and other parts of the raceme, notably the pericarp (which grew at the expense of the seeds within).