1. In intact leaves of Elodea densa illumination resulted in a large increase in the levels of diloroplastic and cytoplasmic ATP and a decrease in chloroplastic and cytoplasmic ADP. Reverse changes were observed on darkening. The kinetics of the fluctuations were similar in chloroplasts and cytoplasm suggesting effective transfer of ATP and ADP between chloroplasts and cytoplasm. Ratios of ATP ...

Spinach leaf chloroplasts isolated in isotonic media (330 millimolar sorbitol, -1.0 megapascals osmotic potential) had optimum rates of photosynthesis when assayed at -1.0 megapascals. When chloroplasts were isolated in hypertonic media (720 millimolar sorbitol, -2.0 megapascals osmotic potential) the optimum osmotic potential for photosynthesis was shifted to -1.8 megapascals and the chloropla...

Clhloroplasts are known to change their volume in vitro by 3 mechanisms. Light and osmotic pressure appear to be the most significant factors for controlling chloroplast volume. The simplest tvpe of volume change shown by isolated chloroplasts has been described by Nishida (8), who found by absorbancy, gravimetric, and volumetric techniques that chloroplasts change their volume in response to e...

Turnover of dysfunctional organelles is vital to maintain homeostasis in eukaryotic cells. As photosynthetic organelles, plant chloroplasts can suffer sunlight-induced damage. However, the process for turnover of entire damaged chloroplasts remains unclear. Here, we demonstrate that autophagy is responsible for the elimination of sunlight-damaged, collapsed chloroplasts in Arabidopsis thaliana ...

Light-grown cells of Ochromonas danica, which contain a single chloroplast per cell, were labeled with [methyl-(3)H]thymidine for 3 h (0.36 generations) and the distribution of labeled DNA among the progeny chloroplasts was followed during exponential growth in unlabeled medium for a further 3.3 generations using light microscope autoradiography of serial sections of entire chloroplasts. Thymid...

Spinach chloroplasts induced the photoreduction of cytochrome c and photooxidation of epinephrine, both of which depended on oxygen and were inhibited by superoxide dismutase. This confirmed the univalent reduction of molecular oxygen in illuminated chloroplasts. In the presence of cytochrome c, hydrogen peroxide formation by chloroplasts was inhibited completely. Rates for the photoreduction o...

Chloroplast function in photosynthesis is essential for plant growth and development. It is well-known that chloroplasts respond to various light conditions. However, it remains poorly understood about how chloroplasts respond to darkness. In this study, we found 81 darkness-responsive proteins in Arabidopsis chloroplasts under 8 h darkness treatment. Most of the proteins are nucleus-encoded, i...

Chloroplasts can be isolated from higher plants directly following homogenization; however, the resulting yield, purity, and intactness are often low, necessitating a large amount of starting material. This protocol is optimized to produce a high yield of pure chloroplasts from isolated Arabidopsis protoplasts. The two-part method is a simple, scaled-down, and low-cost procedure that readily pr...

Ultrastructural changes in in vitro ageing spinach chloroplasts have been studied in detail. Prolonged storage caused swelling of the chloroplasts due to the increase in the thickness and spacing of the thylakoid membranes. The increase in the thickness of the membrane is partly accompanied by the release of lipids. Addition of crystalline bovine serum albumin was found to stabilize the membran...