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Three pigment lines of the tomato cultivar ‘Pearson’ with isogenic backgrounds were studied to determine the relationship between certain carotenoids and the development of chromoplasts during fruit ripening. The lines were normal red (r+/r+), in which about 90% of the carotenoids in the ripe fruit is lycopene; high‐beta (B/B) mutant, in which beta‐carotene is the major pigment and the mature fruit color is deep orange ; and low‐pigment (r/r) mutant, in which carotenoids are drastically reduced and the mature fruit is pale yellow‐orange. This paper reports pigment analyses for the three lines and the ultrastructural changes in plastids of the two mutant lines. Very young, pale green fruits contain proplastids with limited lamellar structure. As the fruits reach the mature green stage, the plastids in all three lines develop into typical chloroplasts. Differences in pigment content and in ultrastructure among the lines are not apparent until ripening commences. In the low‐pigment mutant carotenoids are reduced as ripening progresses and no carotenoid crystalloids are formed. As chlorophyll decreases the fruits become pale yellow. The grana become disorganized and the thylakoids appear to separate at the partitions and tend to be arrayed in lines, some still with their ends overlapping. Globules increase slightly in number. In the high‐beta mutant the grana break down during ripening and globules increase greatly in size and number. Beta‐carotene, presumed to be largely in the globules, crystallizes into elongated or druse type forms which may distort the globules. The crystals may affect the shape of the chromoplasts; long crystals may extend the length of the plastid to over 15 μ. Thylakoid plexes with a regular lattice structure sometimes occur in the chromoplasts of the high‐beta mutant. Granules resembling aggregations of phytoferritin particles occur in the chromoplasts of both of these mutants.

Developing chromoplasts in the fruit of Capsicum annuum were examined by electron microscopy. Special attention was given to changes in the thylakoid system. All grana and some intergranal thylakoids in the mature chromoplasts of the seven cultivars studied underwent lysis. The particulate nature of the granal membranes disappeared during lysis before the relationship between the partitions and locules was obscured. The changes during lysis support the globular concept of membrane structure. The selective lysis of the synaptic membranes of the granal partitions may be attributed to their distinctive composition and structure. Lipid globules (osmio‐philic) did not accumulate in the immediate region of granal lysis, indicating that they are not directly derived from membranes undergoing degradation. During and following granal lysis a profuse development of intergranal thylakoid membranes occurred in several cultivars. In some instances a thylakoid plexus (prolamellar body) was formed. This specialized structure of the thylakoid system occurs in the chromoplasts of other species as well as in other types of plastids. Extensive, concentrically arranged thylakoid sheets with specific interspaced membrane relationships were frequently associated with the plexus. Several types of membrane associations and interrelationships in the plastid are described. An analysis of one type of membrane configuration, the thylakoid sheets, indicated that one method of growth may be through intussusception into the original membrane. The development of thylakoid plexes and of extensive thylakoid sheets during or after granal lysis indicates that dynamic synthetic activities occur in the chromoplasts of some cultivars of pepper during fruit ripening.

This report of the general symptoms of blossom-end rot in the tomato describes in detail the anatomical aspects of the. disorder. The inception of the rot was observed in field-grown San Marzano tomatoes in relation to the age and development of the fruit. Incipient stages of the rot occurred about 10 to 15 days after anthesis when the fruit was from 38 to 60 per cent full grown in length. During this phase of fruit development the increments of growth in length are very large in relation to the size of the fruit. In general, affected fruits are retarded in length growth. The externally visible and the deep-seated symptoms of the rot may occur separately or together in the same fruit at the distal end. The symptoms involve a progressive necrosis of the tissue with subsequent partial dehydration of the affected area. Variations in the lesions are described. The highest incidence of the rot involved over 55 per cent of the fruit. The first indication of the externally visible lesions is the development of brown proteinaceous inclusions in the epidermal and more deepseated cells of the pericarp. These necrotic cells may collapse and a wound healing response is usually evoked in the adjacent living tissue. Cells showing a wound ing response may become necrotic, thus extending the lesion. Light-yellow to brown proteinaceous inclusions also occur in the cells of the deep-seated lesions, particularly in parenchyma cells associated with the vascular bundles of the placental axis. The cells of affected fruits are often glutted with starch grains. No histological evidence was found to support the view that water stress is a primary cause of the disorder. Calcium analysis of the fruit confirms earlier reports that the calcium content of the fruit as a whole is low. The distal end of the fruit, the site of blossom-end rot, is particularly low in calcium. Histological and cytological observations of normal and affected fruits are in agreement with some earlier reports on calcium deficiency in the tomato and other plants. This study implicates calcium deficiency in the fruit as the basic cause of blossom-end rot.