KCET 2019 Biology Solved Paper

The plants have evolved mechanisms by which they can defend themselves against the insects. These can be morphological features or biochemical and physiological adaptations
Morphological adaptations: These include presence of hairy leaves in cotton which protects it from jassids while those in wheat protect it from cereal leaf beetle.
Biochemical and physiological adaptations: When challenged by insects or pathogenic microorganisms, a plant initiates a set of hypersensitive reactions which lead to changes in composition and physical properties of cell walls or by production of secondary metabolites which restrict the insect from further invasion. For example, if nitrogen and sugar content in maize are low along with presence of high amount of aspartic acid, the plant becomes resistant to maize stem borers.