The girth of the stem or root in plants increases due to the presence of:

Given below are two statements: one is labelled as Assertion (A) and the other as Reason (R). Assertion (A): Collenchyma provides mechanical support to growing parts of plants. Reason (R): Its cells have unevenly thickened cell walls at the corners. In light of the above statements, choose the most appropriate answer:

Which of the following tissues remains alive at maturity and is primarily responsible for storage?