Chlorarachniophyta

Five to seven bi-lobed chloroplasts are present inside these algae in a peripheral position. Each chloroplast is bounded by a system of membranes that may appear either as four separate membranes, as a pair of membranes with a sort of flattened vesicles between them, or as three membranes. Four separate membranes are always found near the proximal end of the pyrenoid and over the pyrenoid itself. The outer pair of membranes, when four are present, is referred to as a type of chloroplast endoplasmic reticulum; however, the inner pair is interpreted as the chloroplast envelope. The thylakoids are often loosely stacked in three, with no girdle lamella. Each chloroplast bears a central, pear-shaped pyrenoid projecting inward. Around the pyrenoid, often tightly associated with it, there are vesicles containing β-1,3-glucan, which is the principal storage carbohydrate. A nucleomorph, that contains DNA and a nucleoulus-like body, is present between the second and third envelope of each chloroplast, in a pocket located in the pyrenoid surface. Chloroplasts contain chlorophylls a and b and xanthophylls.

Chlorophyta

The Chlorophyta are not uniform in the ultrastructure of chloroplast, still some generalization can be made. The chloroplasts of these algae are enclosed only by the double membrane of the chloroplast envelope; there is no additional envelope of endoplasmic reticulum or nuclear membrane. In this respect they resemble Rhodophyta and Glaucophyta in the cell compartmentalization. The chloroplasts vary greatly in shape and size. In unicellular forms it is often cup-shaped with a thick base (Dunaliella); in filamentous forms it is often ring-like or net-like shaped and lies against the cell wall (Oedogonium). More massive and elaborate plastids, lying along the longitudinal axis of the cell are particularly characteristic of members of the Zygnematophyceae. Thylakoids are arranged in stacks of two to six or more; their multilayered arrangement may take on the appearance of grana with membrane interconnections, as in higher plants. Girdle lamellae are absent. One to several pyrenoids occur in most of the algae of this division embedded within the chloroplast, and are often penetrated by thylakoids. The DNA organized in small nucleoids is distributed throughout the chloroplast matrix. Both chlorophylls a and b are present; accessory pigments include different xanthophylls such as lutein, zeaxantin, and violaxantin; β-carotene is always present together with other carotenoids.