Delhi Chief Minister Arvind Kejriwal and his cabinet colleagues on the occasion of World Environment Day on Friday took a pledge to support environment conservation.The chief minister planted a sapling at Delhi Secretariat."We must seriously take the pledge to protect nature and imbibe it in our daily life. Environment conservation should be our top priority," Kejriwal said.He also flagged off battery-run cars on the occasion.Deputy Chief Minister Sisodia, other Delhi ministers and Chief Secretary K.K. Sharma too planted saplings in the secretariat complex, an official said.