Tag: tissues: plant tissues

Senescence refers to the loss of functional capacity causing a cellular breakdown and metabolic failure. It is a characteristic feature of the period between reproductive maturity and death of a plant or plant part or cell, which ultimately causes cell death. 

Sclerenchyma cells have thick lignified secondary walls and often die when mature. It provides the main structural support to a plant. They are long and pointed cells. 

Parenchyma is a simple living tissue, which is composed of thin-walled polyhedral, isodiametric living cells with sufficient cytoplasm and one or more nuclei. 

Conduction of food from leaves to other parts of the plant is carried out by phloem cells. 
The synthesis of food is carried out by chlorenchyma cells. These are parenchyma cells with chlorophyll pigments. 

Sclerenchyma is the simple permanent tissue. It commonly forms the protective covering of the nuts and fruits but it also forms the ground tissue which supports different  specialized cells. Their walls consist of cellulose, hemicellulose, and lignin. 

Parenchyma is thin walled, polyhedral, isodiametric, mostly non-lignified, soft living cells with sufficient cytoplasm and one or more nuclei. 

Sclerenchyma cell is a simple permanent tissue which is mainly composed of dead cells. It is the hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation. Their cell walls contain, besides cellulose, a high proportion of lignin. It forms a protective coating on seeds and nuts. Since sclerenchyma cells are dead at maturity, it does not contain plastids. Parenchyma and collenchyma cells are living cells which have plastids.

Sclereids or stone cells are a reduced form of sclerenchyma cells. It has highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants. They are type of sclerenchyma cell that differs from the fibre cell by not being greatly elongated. Often occurs singly (an idioblast) or in small groups, giving rise to a gritty texture in, for instance, the pear fruit, where it is known as a stone cell. May also occur in layers, for example in hard seed coats. A type of cell with thick cell walls, consisting of lignin, that is commonly found on the outer 'skin' of fruits. So, sclereids or stone cells are modified sclerenchyma.

Sclerenchyma is composed of dead tissue which mainly acts as protective coating on fruits and nuts. The reduced form of sclerenchyma cells with highly thickened, lignified cellular walls are known as sclereids. It forms small bundles of durable layers of tissue in most of the plants. 

Senescence is also known as aging. It leads to metabolic degradation. It is the characteristic feature of the period between reproductive maturity and death of a plant or plant part or cell.