A study was conducted on the rooftop of the Administrative Building, Assam Agricultural University, Jorhat during the year 2021-22, with the objective of studying the chlorophyll content and net assimilation rate of petunia (variety-Tritunia star mix) planting on different growing media and pot size in rooftop garden.

The crop is grown in seven growing media with various components by volume in three different pots, viz., S₁: 20 cm, S₂: 25 cm and S₃: 30 cm. The media compositions were G0: Soil (as control), G₁: Soil + Sand + Vermicompost (1:1:1), G₂: Soil + Sand + Cocopeat + Vermicompost (1:1:2:2), G₃: Sand + cocopeat + Vermicompost (2:5:5), G₄: Sand + cocopeat + Vermicompost +Vermiculite (1:2:2:1), G₅: Sand + cocopeat + Vermicompost + Perlite (1:2:2:1), G₆: Sand + cocopeat + Vermicompost + Vermiculite + Perlite (1:2:2:0.25:0.25). The experimental design of the study was factorial Completely Randomized Block Design with three replications. The maximum chlorophyll content of 1.92 mg g^-1 FW and net assimilation rate of 0.023 was recorded for S3G6. Among the pot size, S3 (30 cm) gave the best results in physiological characters.