Palisade parenchyma is absent in leaves of:
Mustard
Soybean
Gram
Sorghum
Sorghum (family-Poaceae) is a monocot plant. The leaves of monocot do not contain palisade parenchyma because the mesophyll of monocot leaf is not differentiated into palisade and spongy parenchyma, all being thin walled, chlorophyllous and irregularly compactly arranged with fewer intercellular spaces.