Chromoplasts in Rosa rugosa: Development and Chemical Characterization of Tubular Elements

Abstract

Abstract 1. Development and fine structure of the chromoplasts in hips of Rosa rugosa have been in­ vestigated by electron and polarizing microscopy. 2. The chromoplasts develop from chloroplasts. During disorganization of the thylakoid system characteristic strutures become visible: ‘oblique’ grana, U-shaped thylakoids, and occassionally ‘thylakoid teeth’ as well as thylakoid anastomoses. - In this early stage, tubules appear in the plastid matrix. They are sometimes connected with membranes, especially with thylakoids. 3. In ripe hips the chromoplasts are packed with tubules. These chromoplast tubules, which attain lengths of up to at least 1.5 μm, are non-ramified and lie parallel to each other. Their diameter is variable, with a mean of 18 nm. They are polygonal in cross-section with electron-dense walls and electron-transparent cores. Association of ellipsoidal osmiophilic globules with the tubules can often be seen. Irregularly swollen remnants of former thylakoids are found in connection with these tubules. In spindle-shaped chromoplasts, the tubules are oriented parallel to the longitudinal axis. Positive birefringence and positive dichroism are observed. 4. The chemical composition of tubule fractions has been analyzed. The tubules contain appreciable amounts of carotenoids, phospho- and glycolipids, and proteins. 5. The origin and development of the tubules is discussed. It appears likely that reorganization of part of the thylakoid system and synthesis of carotenoids are involved in the formation of tubules. 6. The plastids in the yellow autumn leaves of Rosa rugosa contain globules but not tubules.