The marine gastropod molluscs Tridachia crispata, Tridachiella diomedea, and Placobranchus ianthobapsus (Sacoglossa, Opisthobranchia) possess free functional chloroplasts within the cells of the digestive diverticula, as determined by observations on ultrastructure, pigment analyses, and experiments on photosynthetic capacity . In the light, the chloroplasts incorporate H 14CO3 in situ . Reduced radiocarbon is translocated to various chloroplast-free tissues in the animals . The slugs feed on siphonaceous algae from which the chloroplasts are derived . Pigments from the slugs and from known siphonaceous algae, when separated chromatographically and compared, showed similar components . Absorption spectra of extracts of slugs and algae were very similar . The larvae of the slugs are pigment-free up to the postveliger stage, suggesting that chloroplasts are acquired de novo . with each new generation .possess chloroplasts in the cells of their digestive diverticula, and that these chloroplasts are functional in the sense that they photosynthetically fix 14 CO 2 and release the products of photosynthesis to the animal tissues . The chloroplasts may be maintained in a functional state for relatively extended periods of time . Evidence that the structures in the animals are chloroplasts is drawn from their ultrastructure and from a comparative study of pigments in the animals and pigments in known siphonaceous algae .

No abstract

No abstract

Scott, Flora Murray, B. G. Bystrom, and E. Bowler. (U. California, Los Angeles.) Cercidium floridum seed coat, light and electron microscopic study. Amer. Jour. Bot. 49(8): 821–833. Illus. 1962.—The structure of the seed coat of the desert tree Cercidium is typical of the family Leguminosae, but the inner integument is mucilaginous. The characteristic palisade cells of the epidermis and the many‐armed cells of the mucilaginous zone are discussed in detail. The minute wax rodlets on the surface of the young seed fuse later into a film of wax. The epidermal palisade cells are polygonal in transection and the walls are strengthened by cellulose flanges. The palisade cells are enclosed in a thin suberin‐like sheath which connects with the film which lines all air‐filled intercellular spaces in the outer integument. Plasmodesmata extend from the protoplast through the subcuticular zone to the cuticle and also interconnect with adjacent cells through numerous pits in the interflange areas of the main wall. The cells of the inner integument are many‐armed. Intercellular spaces at all stages of growth observed are occluded with mucilage; nevertheless, they are lined with a suberin‐like film similar in reaction to that of the air‐filled intercellular spaces of the outer integument. The distribution of wall materials and ergastic substances was determined by microchemical tests. For electron microscopic study, the epidermis and the mucilaginous zone were fragmented ultrasonically, after chemical treatment when necessary. Cuticular fragments, frequently polygonal in outline, are dense to the electron beam at photographic illumination. When exposed to the electron beam, full‐strength, volatile components are driven off and condense on other wall fragments or on substrate. Unique structures occur in the subcuticular zone, termed here, collar, cone and paddle structure. The basic material of the cell wall as a whole is cellulose impregnated with matrix materials, mainly non‐cellulosic polysaccharides. In addition, lipid‐like substances are conspicuous particularly in the flanges of the palisade cells. Under the electron beam, full‐strength, these substances volatilize and leave the flanges with a blistered outline except in the region of the light line. The volatile substances may be absent from this zone or the microfibrillar structure may prevent distortion. The microfibrillar pattern throughout the length of the flanges is dominantly parallel, but a change to reticulate arrangement occurs in the light‐line region. Numerous pits mark the paths of the plasmodesmata in the subcuticular zone and also through flange and interflange areas of the wall. The dominant microfibrillar pattern in the mucilage cells is reticulate in young and old cells, except for helical orientation in extending arms. Pits occur on arm ends but are infrequent elsewhere. The loose microfibrillar structure presumably allows continuous secretion of mucilage.

No abstract