Keel is the characteristic feature of flower of

Keel is a petal of papilionaceous corolla of Fabaceae members, such as Indigofera. Each flower has two keel petals. These petals are present at the anterior side of the flower, and they may be fused with
each other at their anterior margins to form a boat-shaped structure. This structure encloses the androecium and gynoecium of the flower. Keel petal is also known as carina.
(1) Aloe is a member of Liliaceae which has petal-like perianth lobes known as tepals. These are fused and arranged  n valvate aestivation. These are six in number and present in two whorls.
(2) Petals of tomato are not given special names as all the fi ve petals of its corolla are similar. These petals are fused and arranged in valvate aestivation. 
(3) In tulip of Liliaceae, the perianth lobes are petal-like and are hence called tepals. These are six in number, free and arranged in valvate aestivation.