Question

Which part of the Acacia plant is modified to form spines?

Answer 1

Hint: Acacias are a large genus of shrubs and trees belonging to the subfamily Mimosoid mostly native to Africa and Australia. The main functions of these spines are to reduce transpiration loss, defend against animals, and excellent resistance to drastic weather conditions.

Complete answer: In most plants, thorns, spines, and prickles, are generally called spinose structures. These morphological structures are hard, rigid extensions or modifications of either the leaf, root, stem, or buds that generally serve the same function which is to physically deter animals from eating the plant.
Stipules in plants are outgrowths found on either side of the base of a leafstalk. In some plants, these stipules are modified into other structures or completely absent and are termed as exstipulate plants. Spines can be modified leaves, stipules, or parts of leaves that commonly contain vascular tissue. Spines can be broadly divided into petiolar spines, leaflet spines, or stipular spines. As the name suggests petiolar spines are modification so the petiole, leaflet spines are a modification of the leaf and the stipular spines are a modification of the stipule.
Acacias are a large genus of about 160 species of trees and shrubs belonging to the Fabaceae family. These species of shrubs are native to Australia and Africa, where they are well-known landmarks on the veld and savanna. The most distinct morphological structure of the acacia plant is the presence of sharp spines which are modified stipules of the plant.
Therefore, the spines present in the Acacia plant are considered to be modified stipules of the plant.

Note: The major function of the spines on the Acacia plant are to deter animals, to reduce water loss through transpiration, and withstand extreme temperatures. Not all the species of the Acacia genus have spines, such as long trees of Acacia magnum and Acacia menisci. This species is cultivated as ornamental plants and some even harvest the seeds of certain species and use them as cereals.