Photoperiodic Effect on Vegetative Growth and Flower Quality of Zinnia (Zinnia elegans Jacq.)

The photoperiodic effects on vegetative growth and flower quality of Zinnia (Zinnia elegans Jacq.)were examined during 2015 at the Horticulture orchard, Sindh Agriculture University Tandojam in a three replicated RCBD design. The zinnia plants were grown under four photoperiodic treatments which included T1=Natural photoperiod (Control), T2=4 hours daylight (8 am -12 noon), T3=6 hours daylight (8 am – 2 pm) and T4=8 hours daylight (8 am – 4 pm). The results revealed significant (P 0.05) photoperiodic effect on all the growth and quality traits of Zinnia. The Zinnia grown under 8 hours daylight (8 am – 4 pm) with 38.29 cm plant height, 6.61 side branches plant-1, 41.25 leaves plant^-1, 39.75 days taken to initiate flower bud, 7.49 cm flower diameter, 5.76 g weight of single flower, 3.27 days taken to open 1st flower, 8.41 flowers plant-1, 23.67 days blooming period and 28 percent leaf chlorophyll content. Similarly, photoperiodic treatment comprised of 6 hours daylight (8 am – 2 pm) produced 30.37 cm plant height, 4.36 side branches plant^-1, 23.91 leaves plant^-1, 45.66 days taken to initiate flower bud, 5.37 cm flower diameter, 3.98 g weight of single flower, 5.24 days taken to open 1st flower, 6.50 flowers plant^-1, 16.33 days blooming period and 25 percent leaf chlorophyll content. It was concluded that growing Zinnia under 8 hours daylight (8 am – 4 pm) was an appropriate photoperiod in relation to number of flowers as well as flower quality.