Period Of Cell Enlargement Research Articles

Effects of Plastic Film Mulching on Quality and Appearance of Statuma Mandarin Fruit

Six-year Statuma mandarin (Citrus unshiu Marc. Cv. Miyagawa Wase) trees were used as materials to investigate the effects of plastic film mulching on quality and appearance of Statuma mandarin fruit during three periods of cell division, cell enlargement and mature stages. The results showed that mulching during the cell division and early-mature stages increased total sugar and reduced sugar content of fruit as well as the Vc content, compared to the control. However, the titratable acid content, fruit size, peel weight and single fruit weight were all lower than the control. Film mulching during the cell division phage resulted in higher edible fruit rate, while the fruit shape index was similar to the control. Mulching during the early-mature stage didn’t affect the edible rate of fruit, but caused lower fruit shape index. Compared to the control, film mulching during the cell enlargement period caused lower total and reducing sugar content, titratable acid content and edible rate, while the Vc content was a little bit higher than the control. In addition, the fruit size, peel weight, single fruit weight and fruit shape index were all lower than the control. Mulching during the early-mature period effectively enhanced the content of total and reduced sugar and Vc and decreased the titratable acid content. Hence, it increased fruit quality but had negative effect on fruit appearance.

Longitudinal NMR parameter measurements of Japanese pear fruit during the growing process using a mobile magnetic resonance imaging system

Longitudinal nuclear magnetic resonance (NMR) parameter measurements of Japanese pear fruit (Pyrus pyrifolia Nakai, Kosui) were performed using an electrically mobile magnetic resonance imaging (MRI) system with a 0.2T and 16cm gap permanent magnet. To measure the relaxation times and apparent diffusion coefficients of the pear fruit in relation to their weight, seven pear fruits were harvested almost every week during the cell enlargement period and measured in a research orchard. To evaluate the in situ relaxation times, six pear fruits were longitudinally measured for about two months during the same period. The measurements for the harvested samples showed good agreement with the in situ measurements. From the measurements of the harvested samples, it is clear that the relaxation rates of the pear fruits linearly change with the inverse of the linear dimension of the fruits, demonstrating that the relaxation mechanism is a surface relaxation. We therefore conclude that the mobile MRI system is a useful device for measuring the NMR parameters of outdoor living plants.

Peach Rusty Spot Epidemics: Temporal Analysis and Relationship to Fruit Growth.

Incidence and severity of peach rusty spot were monitored throughout the growing seasons of 1999 to 2001. Graphical and statistical analysis revealed that disease increased from the shuckoff stage of fruit development until 60 days after full bloom; epidemics typically lasted from 17 to 30 days. An analysis of fruit growth indicated that the early-season epidemic coincided with the first stage of stone fruit development, physiologically characterized as the period of cell division. During this period, as fruit growth slowed and approached initiation of pit-hardening, the rate of disease increase slowed. Since fruit infection was greatest during the period of fruit growth, disease progression was modeled as a function of plant growth instead of time. Temporal analysis revealed that the logistic function was appropriate for describing both growth processes, and a synchronous logistic/logistic composite disease progression/fruit growth model was fit to all data sets. No change in disease levels occurred during midseason, which coincided with the second stage of fruit development, a period of slow growth. Subsequently, disease incidence and severity significantly declined on average by 26% and 1.3 lesions per fruit, respectively, during the 20 to 30 days prior to harvest. This decline phase coincided with the third stage of fruit growth, the period of cell enlargement and coloration. These disease reductions may be related to physical changes in fruit size and pigmentation, as opposed to resistance development, causing younger, less established lesions to become undetectable.

Expression of the tomato peroxidase gene TPX1 in NaCl-adapted and unadapted suspension cells

The expression pattern of a peroxidase – (EC 1.11.1.7) encoding gene, TPX1, was studied in NaCl-adapted and unadapted tomato (Lycopersicon esculentum) cells growing in suspension culture. We followed the transcript level during the cell growth cycle and under different salt treatments. There was a cell-cycle-dependent TPX1 expression, the maximum level of transcripts coinciding with the period of cell enlargement in both salt-adapted and unadapted tomato cells. However, enzyme activity of the encoded isoperoxidase was only detected in the culture medium of the salt-adapted cells. NaCl treatment decreased TPX1 transcripts in both cell lines, but the threshold concentration for this down-regulation was higher in adapted cells. In conclusion, salt-adapted tomato cells show significant changes in comparison with unadapted cells in the expression of a gene encoding a cell-wall-targeted peroxidase.

Defoliation increases fruit abscission and reduces carbohydrate levels in developing fruits and woody tissues of Citrus unshiu

Carbohydrate levels in fruitlets of control and defoliated trees of dwarf Citrus unshiu (cvs. Clausellina and Okitsu) were determined from bloom up to the end of fruit set. Full and partial (50%) defoliations were carried out at anthesis and at the beginning of the cell enlargement period. Carbohydrate reserves in woody storage tissues were also analyzed soon after defoliation. In control fruits, sucrose, glucose, fructose and starch showed a transient increase at anthesis and remained low during the cell division phase. Soluble sugars accumulated at the onset of the cell enlargement phase. Defoliation did not modify carbohydrate status in either fruits or woody tissues during the cell division period, although the first fruit abscission wave, which takes place at this stage, was increased. Fruit growth was not altered either. However, at the onset of the second phase of growth, soluble sugars were reduced in fruits and sucrose and starch were lower in woody tissues from defoliated plants. In these plants, fruit abscission at this stage (June drop) was also increased, while fruit growth was arrested or delayed. Once the June drop was overcome, fruits remaining on either defoliated or control plants were similar in size and contained analogous high levels of sugars. Taken together, the results suggest that developing fruitlets are utilization sinks during the cell division period and act as storage sinks during the cell enlargement stage. At this critical transition, sucrose levels correlated positively with fruit growth and negatively with fruit abscission. These results are compatible with the proposal that sucrose supply is a major factor of the regulatory mechanism for citrus fruit abscission during the June drop.

Biosynthesis and Turnover of Cell Wall Glycoproteins during the Vegetative Cell Cycle of Chlamydomonas reinhardii

Abstract Biosynthesis and turnover of the different cell wall components have been studied during the vegetative cell cycle of Chlamydomonas reinhardii by pulse-labelling with [3H]proline and [35S]methionine and by pulse-chase experiments. Two phases of biosynthesis of insoluble cell wall material could be distinguished: 1. de novo synthesis of the daughter cell walls during cytokinesis and 2. cell wall enlargement during cell growth. During the cell enlargement period, a turnover of the insoluble wall component was observed. The released fragments were found to be accumulated in the culture medium. The LiCl-soluble cell wall glycoproteins were found to be precursors of the insoluble cell wall layer. Biosynthesis of the LiCl-soluble cell wall glycoproteins was observed mainly during the time period between cytokinesis and the end of the following cell enlargement period. Labelling of all the cell wall components was found to be strongly reduced during the time period between the end of the growth phase and cytokinesis. During cytokinesis, labelling of the insoluble cell wall material preceded the incorporation of radioactive precursors into the LiCl-soluble wall fraction.

Macromolecules released into the culture medium during the vegetative cell cycle of the unicellular green alga Chlamydomonas reinhardii.

The culture medium of growing Chlamydomonas reinhardii cells contains hydroxyproline-rich glycoproteins, which are mainly liberated during release of the zoospores from the mother-cell wall. Pulse-labelling studies with [3H]proline and [35S]methionine have been performed in order to detect the protein components released by synchronously growing cells at different stages of the cell cycle. When either [3H]proline or [35S]methionine were applied during the phase of cell growth, radioactive label appeared in the released macromolecules after a lag period of 40 min, whereas incorporation into the insoluble part of the cell wall was delayed only by 20 min. When applied at the end of the growth phase, e.g. 13 h after beginning of the illumination period, the radioactive amino acids were incorporated into the cell wall, but radioactive labelling of macromolecules released into the culture medium could not be detected before the zoospores were liberated from the mother-cell wall. Maximal incorporation of [3H]proline and [35S]methionine into the insoluble part of the cell wall was observed during cell division, but essentially no radioactively-labelled macromolecules were released into the culture medium during this time period. Analysis of the macromolecules, which were liberated during cell enlargement, by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed distinct radioactive bands, which were differentially labelled with [3H]proline and [35S]methionine. Among the macromolecules released into the culture medium during cell growth, a component of an apparent Mr 35 000 was preferentially labelled with [3H]proline. This component was also detected after labelling with [35S]methionine, but components of an apparently higher Mr were more prominent after labelling with [35S]methionine. Macromolecules released during the cell-enlargement period of synchronously growing cultures in the presence of [3H]proline contained radioactively-labelled hydroxyproline in addition to proline. These results show that, during cell-wall growth, specific protein components are released into the culture medium and that at least one of these components contains large amounts of proline and hydroxyproline. At least some of these macromolecules seem to be constituents of the cell wall, because during pulse-chase experiments radioactively-labelled macromolecules appeared in the culture medium mainly during the time period when the specific radioactivity of the insoluble inner-cell-wall layer decreased.

Patterns of Hormones, Respiration and Ripening Enzymes during Development, Maturation and Ripening of Cherry Tomato Fruits

AbstractChanges in growth, endogenous levels of hormones, ethylene evolution and cellulytic and pectolytic enzyme activities of cherry tomato fruits (Lycopersicon esculentum Mill. cv. Small Fry) were assayed from anthesis through ripening. After anthesis, growth of cherry tomato fruit follows a three‐dimensional and sigmoid growth pattern which consits of cell division, cell enlargement, mature green, pink and red stages. Cytokinins and auxins were abundant and reached their peak during early development (cell division). Gibberellin levels were more prominent during the period of cell enlargement and reached a peak before the green mature stage. Levels of abscisic acid increased gradually during maturation and reached a maximum in the advanced green mature stage. Respiration pattern was characterized by a climacteric peak at the pink stage. Ethylene production remained less than 2 μl/kg fresh weight an hour until shortly before mature green stage, then rose rapidly to a maximum at pink stage. Activities of cellulytic and pectolytic enzymes were first detected at the green mature stage and increased rapidly during fruit ripening.

Structure and development of fruit and seeds in Chinese gooseberry (Actinidia chinensisPlanch.)

Abstract The development of fruit and seed tissues in Chinese gooseberry (Actinidia chinensis Planch. cv. ‘Monty’) was examined at intervals after flowering. Cell division in all fruit tissues commenced immediately after flowering and persisted in the outer pericarp, inner pericarp, and central core for 23, 33 and 111 days, respectively. The fruit growth curve was double sigmoid owing to an initial period of cell enlargement in all tissues (Stage I, 0–58 day!) followed by a period of retarded enlargement (Stage II, 58–76 days) and a further period of enlargement in the inner pericarp (Stage III, 76–160 days after flowering). The structure of the seed was unusual in that the nucellus possessed a well defined hypostase, and the endosperm and embryo were surrounded by an endothelium. Only one, uniseriate, integument was present which subsequently developed into a thickened tests. The cellular nucellus and endosperm developed concomitantly until the end of Stage II and were absorbed, in part, during Stages II and III by the developing embryo.

Morphological studies on the development of citrus fruits I

Morphological studies on the fruit development of the Early Satsuma orange (Citrus unshiu MARC. var. praecox TANAKA), the Hassaku orange (C. Hassaku Y. TANAKA) and certain other species were made respectively. By comparing these results together with those obtained previously with the Satsuma orange, the general characteristics and specific or varietal differences in the citrus fruit growth were investigated. Noteworthy features of this investigation were as follows:1. In the growing citrus fruit, the peel and the pulp seem to show different growth cycles. At first, the peel increased in thickness rapidly, next came a vigorous growth of the pulp, which was again followed by a decrease in the peel thickness. Thereafter the peel and the pulp grew in harmony with one another.The peel continued to grow for a longer period of time than did the pulp. As the fruit became mature, the decline and the cessation of growth occurred earlier in the pulp than in the peel. It seems that the peel maintains its growth activity even after the fruit maturation, although the extent of this post-maturation activity varies among different forms. This characteristic of citrus was most clearly indicated by the conspicuous growth of the peel in the mature fruit of Shuto, a variety of C. aurantium LINN. during spring and summer.2. In young citrus fruit the peel increased its thickness rapidly when the cell multiplication in the albedo tissue became very vigorous. In the Hassaku orange, which has a thick peel, the albedo tissue cells multiplied more vigorously, continued to do so for a longer period, and as a result became greater in number than in the Satsuma orange.3. The development of citrus fruit was divided into three stages as follows: Stage I, the cell division period; Stage II, the cell enlargement period; and Stage III, the maturation period. The duration of each stage could be determined by external changes associated with the pulp growth. The period from the emergence of juice sacs to the beginning of their remarkable elongation was referred to as Stage I. In the Satsuma orange, it was observed previously that when the juice sacs began to enlarge abruptly most of their epidermal cells also initiated to elongate. This period was therefore referred to as the cell enlargement period, Stage II. Stage III was defined by a conspicuous decline of the growth in width of the pulp segments.The species and varieties of citrus fruits used in the present study differed in the durations of these three stages, whereby they could be arranged in the following order (from the longest to the shortest of each stage): Stage I-Hassaku orange, Early Satsuma orange, Satsuma orange; Stage II-Satsuma orange, Hassaku orange, Early Satsuma orange; Stage III- Hassaku orange, Satsuma orange, Early Satsuma orange. The fruit with longer duration of Stage I grew rapidly in Stage II and attained larger size. The duration of Stage II was not directly related either to the final fruit size or to the time of fruit maturity, while the latter was proportional to the duration of Stage III.4. Despite their larger size, the fruits of Hassaku and Iyokan (C. Iyo TANAKA) contained much fewer juice sacs than did those of the Early Satsuma orange and Satsuma oranges. Consequently, their juice sacs were relatively large, especially so in Hassaku. On the other hand, in every kind of citrus under observation there was a tendency within the same form that the larger the fruit the more juice sacs were found in it. However, the degree of this association was not uniform among different kinds. Thus there were greater regressions of the number of juice sacs on the pulp weight in the Early Satsuma orange or the Satsuma orange than in Hassaku or Iyokan.

Morphological, anatomical, and physiological changes in the developing fruit of the Valencia orange, Citrus sinensis (L) Osbeck

Measurements of fruit radius and peel and pulp width, as well as determinations of fresh weight, dry weight, moisture content total and protein nitrogen content, and respiration rate were made throughout two growing seasons on Valencia oranges from the Gosford district of New South Wales. Soluble solids, sugar, and acid were also determined in the juice. Anatomical changes during development were investigated throughout one season. Development could be divided into three stages, corresponding with changes in growth rate and coinciding on a calendar basis in both seasons. Stage I varied in length according to the date of the blossom, but was completed by mid December. This was the cell division stage; by mid December cell division was completed in all tissues except the outermost cell layers. Increase in fruit size at this stage was mainly due to increased peel thickness. Stage 11, a period of very rapid growth from mid December to mid July, was the critical period for growth and was distinguished as the cell enlargement period, rapid morphological and physiological changes occurring in the absence of cell division. The growth of the pulp was responsible for most of the increase in fruit size during Stage 11; the peel reached a maximum width early in this stage and then became thinner with very little subsequent change in thickness as the pulp continued to increase in size. Stage 111, the maturation period, lasted from mid July until the fruit was ripe, or approximately 7 months. Fruit continued to grow for as long as it was left on the tree but at a very reduced rate compared with Stage 11. Ripening occurred during Stage 111.

INFLUENCE OF THE SIZE OF THE INOCULUM ON THE GROWTH OF CHLORELLA VULGARIS IN FRESHLY PREPARED CULTURE MEDIUM

THE IMPORTANCE of the unicellular green alga, Chlorella vulgaris, to plant physiologists engaged in studies of cellular metabolism and especially of photosynthesis is well known. Relatively few detailed studies have been made of its growth, however. The present paper deals with the growth curve of Chlorella in cultures inoculated with different numbers of cells taken from parent cultures of the same age. Multiplication, or increase in cell number, was used as an index of growth in this work, although it is realized that a period of cell enlargement precedes each division, and that growth is the result of these two processes. MATERIALS AND METHODS.-Cells for the experiments were withdrawn from four-day-old, rapidly growing stock suspensions of Chlorella vulgaris cultured asg previously described (Craig and Trelease, 1937; Pratt and Trelease, 1938) in a solution that contained KNO3, 0.025M; MgSO4 7H20, 0.02M; KH2PO4, 0.018M; FeSO4 7H20, 0.00001M; potassium citrate, 0.00001M; and Zn, Cu, B, and Mn in approximately the concentrations employed by Trelease and Trelease (1935). The initial pH of this solution was 4.45. New stock cultures were started daily so that there was always available a supply of cells of approximately the same physiological age and activity. Cells were separated from the culture medium and were washed in three changes of distilled water by repeated centrifugation and decantation. They were then suspended in distilled water and the density of the population in the suspension was estimated from haemacytometer counts. Inocula containing the desired number of cells were pipetted into 500 ml. Pyrex glass Florence flasks, each of which contained 150 ml. of the standard nutrient solution. The flasks were continuously illuminated from below by a water-cooled battery of twentyfour 50-watt frosted Mazda lamps. The light intensity, measured by means of a Weston photoelectric-cell light meter, Model 603, varied from 21,000 lux to 18,000 lux. The lamps were replaced by a complete new set when the intensity fell below this value. The temperature at the level of the flasks varied from 18? to 220C. A gas mixture containing 5 per cent CO2 and 95 per cent air was bubbled continuously through the solutions. The cultures were shaken vigorously twice daily to insure separation and uniform suspension of the cells. Growth measurements were made periodically by withdrawing small samples from each flask and estimating the cell population from haemacytometer counts. Triplicates of each culture were prepared, 1 Received for publication November 27, 1939. The author is indebted to Miss Jane Fong for valuable assistance in the laboratory. and cell counts were based on the averages of haemacytometer counts of four different samples from each flask. Each point in the figures represents, therefore, the average of twelve samples. The maximum deviation from the mean value occurred in the lower portions of the growth curves and never exceeded 5 per cent. Over the major portion of the curves in all cultures the deviation of individual cultures from the mean value was less than 3 per cent. EXPERIMENTS AND RESULTS.-Figure 1 shows the growth in cultures inoculated with different numbers of cells withdrawn from parent cultures of the same age. Since the points describe sigmoid curves, it seemed of interest to examine the data to ascertain whether they could be represented by the equation characteristic of autocatalyzed monomolecular reactions that has been found, in many cases, to describe reasonably well the growth of populations and of individual organisms (Ostwald, 1908; Robertson, 1908a, 1908b, 1923; Reed and Holland, 1919; Reed, 1920, 1921a, 1921b, 1928a, 1928b, 1932; Gaines and Nevens, 1925; Porterfield, 1928; Pratt, 1936). The differential form of this equation expresses the rate of growth, and may be written