Define-parenchyma,collenchyma n sclerenchyma.
Parenchyma is a simple permanent plant tissue composed of thin-walled, unspecialized cells separated by intercellular spaces and which have not lost their power of division.
Collenchyma is a simple permanent plant tissue containing cells characterized by cell walls unevenly thickened with cellulose and hemicellulose and functioning mainly as flexible and supportive tissue.
Sclerenchyma is also a simple permanent plant tissue containing dead cells with heavily lignified cell walls and functioning as a strengthening tissue.