Pinnularia (Bacillariophyta) | General Cell Characteristics of Pinnularia

 Pinnularia 

(Bacillariophyta)

General Cell's Characteristics of Pinnularia:

• Pinnularia is a freshwater alga. It is found in the pond. 
• It is also present in moist soil.
• Pinnularia is an unicellular organism. 
• It consists of elongated and elliptical cells. 
• The cell wall is mainly composed of pectic substances and silica is impregnated in the cell wall. Therefore, their wall becomes very hard. 
• The cell wall is composed of two halves called valves or theca. 
• These halves overlap like a Petri dish. 
• The margins of the two valves are covered by a connecting band or girdle band. 
• The two valves with their inner protoplasts are called a frustule. 
• The frustule has two views. The surface view is called the valve view and the band view is called the girdle view. 
• The outer larger valve is called epitheca. 
• The smaller inner valve is called the hypotheca.
• Cytoplasm is arranged in the parietal layer. 
• A large central vacuole is present inside the cell. 
• A single nucleus is suspended in the center near the vacuole by the transverse cytoplasmic bridge. 
• Two chloroplasts are present along the two sides of the cells. These are the most prominent structures. They contain chlorophyll a, c, beta-carotene, and diatomic or fucoxanthin pigment. Fucoxanthin gives the alga characteristic color.
• One or two pyrenoids are present in the chloroplast. But they do not synthesize starch. 
• Their storage compound is oil or chrysolaminarin.
• Locomotory organs are absent in Pinnularia. It moves by characteristic gliding movements.