Portal de Periódicos da CAPES

The ultrastructure of chromoplast development in red tomatoes

1968; Academic Press; Volume: 25; Issue: 3-4 Linguagem: Inglês

10.1016/s0022-5320(68)80076-0

1878-2345

Samuel W. Rosso,

Plant Reproductive Biology

Plastid morphogenesis in ripening red tomato fruit tissues has been studied by light and electron microscopy. Color changes of the fruit flesh result from the metamorphosis of chloroplasts 3–6 μ in diameter into chromoplasts 15–48 μ in length and 1–2 μ in diameter, which accumulate lycopene as the major pigment component. In most of the red-fruited varieties examined, the chloroplast starch reserves and granal thylakoids disappear prior to or during the initiation of one or more pigmented crystalline plates. Retention of grana in many nearly mature chromoplasts of the Green Flesh mutant is apparently correlated with the continuation of chlorophyll synthesis in the ripening fruit. The crystalline plates are interpreted as flattened membranous sacs (thylakoids) that are usually initiated in close association with membranes apparently persisting from the chloroplast progenitor. Increased longitudinal growth of a given plate is thought to cause overall plastid elongation; transverse growth is accompanied by involution of the lateral edges of the membranous sac to produce a tubular, crystalline, myelinic configuration, which causes little increase in plastid diameter. Simultaneous growth of several plates within a single chromoplast may result in the inclusion of one tubular crystal within another, thus forming a “compound crystal.” The small tablet- or needle-shaped chromoplast crystals found in certain specimens were not typical of the specimens used in this study and therefore are treated only superficially. Even in the very late stages of chromoplast differentiation, the crystals and remaining stroma are surrounded by an intact plastid envelope, which can be consistently demonstrated at the ultrastructural level.