Tomato Fruit Tissue Research Articles

The ultrastructure of chromoplast development in red tomatoes

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.

Production of Carbonyl Compounds by Tomato Fruit Tissue in the Presence of Aliphatic Alcohols

IT is well established that, in the absence of oxygen, many types of plant tissue produce ethanol. Under normal conditions, ethanol, other alcohols and various aldehydes are produced in small amounts by ripening fruits and other plant organs1–3. The question whether ethanol is metabolized by plant tissues has, on the other hand, been a source of controversy. In recent years Phillips4, working with barley seedlings, Wager5 with peas and Lowe and James6 with mature carrot disks have found no evidence for appreciable utilization of ethanol. However, Cossins and Turner7–9 showed that ethanol was consumed by the tissue in germinating peas and was converted initially to acetaldehyde and acetone, followed by the production of organic acids and amino-acids. Homogenates of a variety of germinating seeds were shown10, by redox indicator, to have alcohol dehydrogenase activity when the normal C2−, C3− and C4− aliphatic alcohols were added as substrates. Less activity was evident in the presence of the normal C1− or C5−, secondary C3− or iso-C4−, and tertiary C4− or C5− alcohols. Recently, Cossins and Beevers11 showed that carrot disks, corn and pea shoots, potato disks and castor bean endosperm rapidly metabolized carbon-14-labelled ethanol, while apple tissue consumed it very slowly. Their results suggested that acetyl coenzyme-A was derived from ethanol and converted to lipids, amino-acids, organic acids and sugars by known pathways.

Cellulase activity in sterile tomato fruits.

SAMISH et al.1 reported that “bacteria are found quite regularly within the tissue of apparently healthy tomatoes”. Since some of the family types they found have species which produce cellulase2, it was deemed necessary to determine beyond doubt that the cellulase reported by Hall3 was produced by the tomato fruit tissues and not by micro-organisms which might be within the fruits.

Effects of Wounding on Respiration and Ethylene Production by Cantaloupe Fruit Tissue

Despite the difficulty of evaluating the effects of handling and wounding, tissue slices offer advantages for physiiological or biochemical tests where small quantities of uniform tissues are required. This paper provides information on behavior of tissue slices from cantaloupe fru,its, including the changes induced by wounding. Respiration, ethylene production, and the effect of applied ethylene on respiration were measured, and the responses of tissue slices from cantaloupe fruits of various chronological ages were compared with the responses of matched intact fruits. It is well-known that wounding of plant tissue increases the rate of respiration (1, 5, 16), and may induce chemical changes and meristematic activity in the region of the wound (2, 3). Even shaking or dropping can cause an increase in respiration in avocado and citrus fruits (1, 9). Much information has been accumulated on changes in tissue cut from tubers and tuberous roots (12, 13, 15), but information on cut or wounded tissue from fruits is limited. The response of fruit tissues to wounding is variable and is influenced by varieity and maturity (1, 10, 19, 20, 24). Other sources of variability are fruit size, morphology, and the permeability of the peel to gases. According to various authors (1, 10, 22), increased CO2 evolution soon after cutting may indicate improved ventilation of the organ, rather than a direct effect of the wound on the cells involved. At least part of the burst of CO2, produced by apples immediately after cutting, may be eliminated by pre-evacuation of the tissue (5). Studies by Burg and Thimann (7) and Burg (5) emphasized the importance of the time elapsed after cutting in interpreting the effects of wounding. Cutting or wounding generally causes increased production of ethylene and -other volatiles by fruit tissue (11, 18). However, although Burg and Thimann (7) found an increased respiratory rate in tissues cut from postclimacteric apples, the rate of ethylene production was the same in plugs of tissue as in whole fruits, and the production by slices was appreciably lower. Release of existing ethylene fr'onj tissues may account for most of any increased production apparent just after cutting (5). When apple tissue was soaked in water or hypotonic solutions, Burg and Thimann (7) found that ethylene production was depressed, but the respiration rate was not affected; hypertonic solutions prevented the inhibition of ethylene production. Even during short periods of immersion, apple tissue loses appreciable amounts of fresh and dry weight (7, 10). Only avocado, banana, and tomato fruit tissues have been reported as stored for more than 2 days (1, 4, 5,). Avocado and banana tissue portions. showed normal ripening changes when stored in moist air, but such were not reported for tomato tissue. Infection by microorganisms may be a factor in the increased res,piration and ethylene production rates shown by cut tissue. While Petiicillkum digitatumii is the only microorganism known to produce relatively large amounts of ethylene (26), Williamson (25) has found that the growth of disease organisms may stimulate ethylene production by several plant materials; this response, which he attributed to injury, occurred as long as the infected tissue was alive. The following factors must be considered in the planning and interpretation of studies on ethylene production and respiration rate when fruit tissue slices are used: possible detrimental effects from washing or from immersion of the tissue in water, the length of time between cutting the tissue and the measurement of respiration and ethylene production rates, potential contamination from microorganisms, and the state of fruit maturity or ripeness.

The Effect of Low Temperature on Phosphate Esterification and Cell Membrane Permeability in Tomato Fruit and Cabbage Leaf Tissue

Exposure to O�C for 4 weeks caused a threefold increase in cell membrnno permeability of mature-green tomato fruits (susceptible to chilling injury) hut had no effect on that of cabbage leaves (not susceptible). While tomato fruits chilled for 12 days lost two-thirds of their capacity to esterify phosphate at 20�0, a steady rise in this capacity occurred during chilling of cabbage leaves for 5 weeks. In tomato fruits the rate of phosphate esterification at the chilling temperature fell in 12 days to about one-half of the rate at the commencement of chilling .. It is suggested that the characteristic symptoms of chilling injury in mature-green tomato fruits, viz. increased susceptibility to fungal attack and loss of the capacity to ripen normally. may result from an energy deficit caused by a chilling. induced reduction in the phosphorylative capacity of the tissue.

ASCORBIC ACID IN TOMATOES: I. DISTRIBUTION AND METHOD OF ASSAY

A procedure for preparing an extract of tomato fruit tissue prior to ascorbic acid assay is described which will give acceptably accurate results in spite of the extreme variations in concentration often found in the natural product. Fluctuations in ascorbic acid levels of developing greenhouse tomatoes have been measured as well as varietal differences of this constituent. A wide range in concentration was found between various tissues of a single fruit and between individual freshly harvested fruits. Storage of the intact fruit had little effect on the ascorbic acid level.