Plant growth regulators (PGRs) are used in cotton production to optimize yield and quality and even suppressing excess growth whenever necessary. Experiments were conducted in 2017 at Cotton Seed Multiplication, Training and Research Farm, Sreepur, Bangladesh to study the response of cotton yield and quality to different plant spacings, concentration and time of application of mepiquat chloride (MC) growth regulator. Plant spacings like 45 cm × 30 cm, 60 cm × 30 cm and 75 cm × 30 cm; MC spray @ 1.0, 2.0, 3.0 and 4.0 ml  L-1  water at 25, 50 and 75 DAE for each concentration along with water spray as control, were the treatment variables. The maximum LAI (0.80) was obtained from 75 cm × 30 cm spacing and the minimum LAI (0.74) was from 60 cm x 30 cm spacing. LAI was maximum (0.90) for plants grown without MC. Plants grown with application of MC 2 ml L-1 water at 25 DAE produced the minimum (0.64) Leaf area index evaluated highest (1.06) from 2 ml MC L-1 water sprayed at 25 DAE with 60 cm x 30 cm spacing and lowest (0.52) from 2 ml MC L-1 water at 25 DAE with 45 cm × 30 cm spacing treatment combinations. So, cotton cultivation in Sreepur, Gazipur areas may be accelerated with foliar application of mepiquat chloride @ 2 ml L-1 water at 25 DAE along with plant spacing of 60 cm x 30 cm for higher yield and quality.

Key words: Plant spacing, growth regulator, time of foliar, leaf area index, cotton.