Peak Of Ethylene Production Research Articles

Climacteric and non-climacteric behavior in melon fruit: 2. Linking climacteric pattern and main postharvest disorders and decay in a set of near-isogenic lines

A set of near-isogenic lines (NILs) of melon ( Cucumis melo L.) was used to test the relationship between the climacteric pattern and postharvest disorders at harvest and after 30 days at 8 °C. The NILs contained different chromosome introgressions in the linkage group III from the non-climacteric exotic Korean accession PI 161375 transferred into the genetic background of the non-climacteric Spanish cultivar ‘Piel de Sapo’ (PS). A quantitative trait locus (QTL) in this linkage group induced climacteric behavior in eight NILs accompanied by a peak of ethylene production and fruit dehiscence to different degrees. The cultivar ‘Nicolás’ and one NIL showed a non-climacteric pattern of respiration rate and ethylene production. The climacteric NILs were used to test the relationship between this pattern and postharvest disorders. The reference climacteric lines ‘Fado’ and ‘Védrantais’ were more sensitive to CI and associated Cladosporium rot than the NILs or PS. In general, a more intense climacteric behavior was accompanied by fruit dehiscence, and higher total losses and greater skin scald after storage, than in PS. A higher incidence of chilling injury (CI) in the climacteric NILs was found compared with the non-climacteric ones, although with exceptions (one NIL for CI in the form of scald; the same NIL and one more for pitting). The climacteric onset and netting scald were not related, and CI in the form of skin spots was only found in climacteric NILs and was positively correlated with the maximum peak of ethylene production. Some climacteric NILs did not follow the rule of a higher susceptibility to other disorders and decay after storage compared with PS, such as for example in fruit over-ripening (detected externally or internally), Cladosporium rot at the peduncle and Alternaria rot. Mealiness was independent of climacteric behavior. Three climacteric NILs obtained better flavor scores after storage than PS, although the maximum peak of ethylene production was positively correlated with off-flavor. Genotypic correlation between disorder data and the physiological data of climacteric fruit revealed positive (flavor index) or negative postharvest consequences (skin injuries, rots or off-flavors). At least one QTL can be assigned to most of the quality traits analyzed.

P-type H +-ATPases activity, membrane integrity, and apoplastic pH during papaya fruit ripening

The P-type H +-ATPase activity and related apoplastic pH were analysed in papaya fruit ( Carica papaya L. cv. Golden) at different stages of maturation. Postharvest ripening of papaya was characterized by ethylene emission, skin colouration, firmness, and titratable acidity (TA). The climacteric peak of ethylene production occurred on the 2nd day after harvest, along with a sharp decrease in ATP hydrolysis and a transient alkalization of the apoplast fluid. Such effects were consistent with progressive cell membrane deenergization occurring concomitantly with fruit softening and decrease of cell membrane integrity as manifest by electrolyte leakage. Nevertheless, it was possible to detect an expressive ATP-dependent H + gradient 2 days after the climacteric suggesting the maintenance of cellular function even in the late stages of the fruit ripening. The data provide new insights into the physiology of ripening in papaya and how that P-type H +-ATPase activity can be used as a biochemical marker for postharvest analysis and management of climacteric fruit.

Stage- and tissue-expression of genes involved in the biosynthesis and signalling of ethylene in reproductive organs of damson plum ( Prunus domestica L. subsp. insititia)

In this work, four cDNA clones ( Pd-ACS1, AJ890088; Pd-ETR1 and Pd-ERS1, AJ890092, AJ890091; and Pd-CTR1, AJ890089) encoding an ACC-synthase, two putative ethylene (ET) receptors, and a putative MAPKKK, respectively, were isolated and phylogenetically characterized in Prunus domestica L. subsp. insititia. Their expression was studied by real-time PCR during flower (closed, open and senescent) and fruit ( early green, late green, maturation and ripening) development of damson plum, which is climateric. While two peaks of ET production were quantified at early green and ripening stages in whole fruits, the seed was not able to produce it during maturation and ripening stages. All studied genes were differentially expressed during flower and fruit development. In general, the level of transcripts of Pd-ACS1 was higher in fruits than in flowers. However, it was noteworthy that: (1) Pd-ACS1 expression was hardly detected in closed flowers and at low levels during early green stage; and fruit development provoked a notable differential expression in seeds, and pericarp; (2) the results of Pd-ACS1 expression during fruit development suggest a preponderant role of this gene from late green stage onward. The stamen was the only floral organ in which expression of both Pd-ETR1 and Pd-ERS1 receptor genes was not significantly altered during development; however, their expression decreased concomitantly with development of pistil (only floral organ to register a net ET production when fertilized) and during first days of ovary development (the highest ET production during all fruit development). Contrary to Pd-ERS1, the level of Pd-ETR1 mRNA was temporally quite similar in the seed. With regard Pd-ETR1, even its expression was very scarce during maturation of mesocarp, was stimulated during ripening. In the epicarp, Pd-ERS1 and Pd-ETR1 were low expressed during pit hardening increasing onward and decreasing during ripening. Pd-CTR1 expression was in the seed > mesocarp > > epicarp. Spatial and temporal levels of Pd-ACS1, Pd-ETR1, Pd-ERS1 and Pd-CTR1 mRNAs described in this work demonstrate that the expression of these genes is not always constitutive and that control of its transcription may play an important role in regulating the development of reproductive organs of damson plum.

Behavior of arazá (Eugenia stipitata Mc Vaugh) fruit quality traits during growth, development and ripening

The period between fruit set and full ripening of arazá fruit grown in the Colombian Amazonia was 55 ± 5 days. Three stages of a sigmoidal growth were identified and longitudinal and equatorial traits fitted a logistic model better than three-degree polynomial models. Fruit growth clearly exhibited three different physiological stages, identified as follows: S1, involving cellular division during the first 14 days; S2, maximum fruit growth, during which cellular expansion took place (up to day 50), and a final S3 state of 5 days to reach physiological maturity. After this time, the fruit can be harvested with a dull green coloration. Parenchyma was the principal fruit tissue, and no support tissues (sclerenchyma or collenchyma) were evident. The respiratory pattern of arazá fruit was climacteric, with maximum respiration rates of around 200 mg CO2 kg−1 h−1, preceded by a peak of ethylene production (20 μL C4H4 kg−1 h−1), a change in skin color from green to yellow, a total soluble solids value of 5°Brix, an increase in the sucrose and fructose content up to 2.8 μmol g−1, a pH which increased to 3 units, and a decrease in titratable acidity to 400 mmol H+ L1−. Malic acid was the main organic acid in the edible pulp and ascorbic acid was present in a concentration of 17.8 μmol g−1. Skin color (as measured by hue angle) combined with titratable acidity and fruit firmness can be recommended as harvest indices for arazá fruit.

Ripening and quality of 'Golden' papaya fruit harvested at different maturity stages

The objective of this study was to determine how ripening physiology and quality of 'Golden' papaya are affected by maturity stages at harvest. Papayas were harvested at four maturity stages (Stage 0: totally green; Stage 1: up to 15% of yellow skin; Stage 2: 16-25% of yellow skin; Stage 3: 26-50% of yellow skin) and evaluated during ripening at 23ºC. Physical and physico-chemical (skin color, pulp firmness, soluble solids, titratable acidity, and ascorbic acid), physiological (respiratory activity and ethylene production), and sensorial (flavor, odor, firmness, and appearance) characteristics were evaluated. Regardless of maturity stages, fruit showed similar variation in respiration rate, exhibiting constant values after the 2nd day of storage at 23ºC (~31 mL CO2 kg-1 h-1 for stages 0, 1, and 2, and ~37 mL CO2 kg-1 h-1 for stage 3). Typical climacteric behavior was not observed for any maturity stage. Only fruit harvested at stage 0 and 1 showed a well defined ethylene production peak of 2.1 µL C2H4 kg-1 h-1 after 7 d of storage and 1.3 µL C2H4 kg-1 h-1 after 6 d, respectively. Fruit harvested at stages 0, 1, 2 and 3 reached the edible condition (pulp firmness < 20 N) after 7, 6, 4, and 3 d at 23ºC, respectively. The ascorbic acid concentration increased 20-30% during ripening, while skin hue angle and titratable acidity was reduced. Independent of the maturity stages at which papayas were harvested, soluble solids did not alter during ripening. Fruit harvested at stages 2 and 3 had superior scores for sensorial evaluation, mainly for flavor and appearance. Harvest at different maturity stages altered fruit postharvest physiology and when effectuated at early stages, it reduced fruit quality but did not make its consumption unacceptable.

Involvement of 1-methylcyclopropene in ripening of harvested mei (Prunus mume) fruit

SummaryHarvested mei (Prunus mume) fruit were stored at 20°C after exposure to 500 nl l–1 1-methylcyclopropene (1-MCP) for 8 h. Firmness, peel colour, chlorophyll content, chlorophyllase activity, soluble solids content (SSC), titratable acidity (TA), respiration and ethylene production, and cell wall hydrolysis enzyme activities were monitored to determine the efficacy of 1-MCP treatment in delaying mei fruit ripening compared to untreated control fruit. Results showed that control ‘daqinghe’ mei fruit displayed typical climacteric patterns of respiration and ethylene production. Peak CO2 production and ethylene production were observed after 6 d. Fruit softening was accompanied by a progressive decrease in colour parameters expressed as hue angle (h°), chlorophyll content, SSC, TA and increases in chlorophyllase, pectin methylesterase (PME) and polygalacturonase (PG) activities. 1-MCP treatment prior to the climacteric increase significantly delayed the onset of the climacteric peaks of CO2 and ethylene production. These delays were associated with reductions in fruit softening, consistent with delaying the activities of PME and PG. Fruit treated with 1-MCP exhibited less peel colour change from green-to-yellow because of their lower levels of chlorophyllase activity and less chlorophyll breakdown. Moreover, 1-MCP treatment also significantly retarded reductions in SSC and TA compared with control fruit. The shelf-life of mei fruit ripening was increased by 4 d following 1-MCP treatment. Thus, 1-MCP treatment can markedly extend the post-harvest life of ‘daqinghe’ mei fruit.

ETHYLENE IS REQUIRED FOR THE RIPENING OF GRAPE

While grapes have been classified as a non-climacteric fruit, we show here that endogenous ethylene production just before veraison is required for an increase in berry size and possibly for anthocyanin accumulation in the ripening berry. Our data also show that the peak of ethylene production just prior to veraison is associated with increased accumulation of ACC oxidase mRNAs, enhanced ACC oxidase activity and higher concentrations of malonyl-ACC. Exposure of clusters to 1-MCP at various times before and after veraison inhibited ripening only in fruit treated at the time of the ethylene peak. Lastly, we observed some feed-back at the ethylene perception level and this response is discussed in relationship to the behaviour of non-climacteric plant tissues.

Qualidade pós-colheita de melão Galia submetido à modificação da atmosfera e ao 1-metilciclopropeno

Avaliou-se o amaciamento da polpa, a formação da região de abscisão do pedúnculo, o comportamento respiratório, a produção de etileno e a qualidade de melão Galia 'Solar King' sob influência de atmosfera modificada (AM) e 1-metilciclopropeno (1-MCP), durante o armazenamento a 7,6±1,1ºC e 87,6±6,3% UR seguido de temperatura ambiente (24,2±0,7ºC e 88,1±5,4% UR). Os frutos, provenientes do Polo Agrícola Mossoró-Assu (RN), foram submetidos a tratamentos pós-colheita [controle, AM (X-TendTM), aplicação de 1-MCP (300 nl L-1) e AM (X-TendTM) seguida da aplicação de 1-MCP (300 nl L-1)] e a tempos de armazenamento (0, 7, 14, 21, 24, 27 e 30 dias). O delineamento experimental foi inteiramente casualizado, em fatorial 4x7, com quatro repetições. Aos 23 dias, a atividade respiratória dos frutos tratados com 1-MCP foi menor que a dos demais, mantendo-se praticamente estável a partir do 25ºdia. Os tratamentos AM ou 1-MCP resultaram em picos de produção de etileno menores e precoces. Nos frutos sob AM, tratados ou não com 1-MCP, a perda de peso foi menor. Porém, a associação AM+1-MCP foi mais vantajosa porque resultou em frutos mais firmes. O efeito mais evidente da aplicação de 1-MCP foi no atraso da evolução da abscisão do pedúnculo. A melhor aparência interna foi observada nos frutos tratados com 1-MCP e sob AM+1-MCP. Portanto, esta associação permitiu a melhor preservação da qualidade dos melões.

The climacteric-like behaviour of young, mature and wounded citrus leaves

Although leaves and other vegetative tissues are generally considered as non-climacteric, citrus leaves show a climacteric system II behaviour after detachment. Upon harvest, young, fully expanded 'Valencia' orange (Citrus sinensis) leaves ( approximately 60-d-old) exhibited two phases of ethylene production. The first phase, up to 6 d after detachment, was characterized by a low and constant ethylene production (system I pathway), associated with a constitutive expression of ACC synthase 2 (CsACS2), CsERS1, and CsETR1. ACC synthase 1 (CsACS1) was not expressed during this phase and autoinhibition of ethylene production was apparent following treatment with exogenous ethylene or propylene. The second phase, 7-12 d after detachment, was characterized by a climacteric rise in ethylene production, preceded by the induction of CsACS1 and ACC oxidase 1 (CsACO1) gene expression in the system II pathway. This induction was accelerated and augmented by exogenous ethylene or propylene, indicating an autocatalytic system II ethylene biosynthesis. Mature leaves (6-8-months-old) behaved similarly, except that the climacteric peak in ethylene production occurred earlier (day 5). Young and mature leaves varied in the timing of the climacteric ethylene rise and CsACS1 and CsACO1 induction. The two phases of ethylene production, system I and system II, were also detected in wounded leaf discs of both young and mature leaves. The first phase peaked 15 min after excision and the second phase peaked after 6 h.

Ripening and quality responses of mamey sapote fruit to postharvest wax and 1-methylcyclopropene treatments

Abstract Mamey sapote (Pouteria sapote (Jacq.) H.E. Moore and Stearn) fruit is highly appreciated in the Caribbean region; however, marketable life is significantly limited by abrupt softening during postharvest handling. Postharvest wax and 1-methylcyclopropene (1-MCP) treatments were evaluated for potential of extending mamey sapote postharvest life. Fruit of the cv. Magana were harvested at mature green (G), light orange (LO) and orange (O) stages of the pulp color, and brushed to remove excess epidermal fiber. Waxed (carnauba emulsion) and unwaxed fruit (G and LO stages) were held at 13 °C for 7 days, then transferred to 20 °C for ripening; those at O stage were held constantly at 20 °C. In a subsequent test, ‘Magana’ fruit were harvested at a preclimacteric stage (LO), brushed, and treated with ±carnauba wax and ±1-MCP (1 μl l−1 at 20 °C for 24 h). Fruit from all treatments were subsequently stored at 20 °C and 85–90% relative humidity. Unwaxed ‘Magana’ fruit reached climacteric maxima in 10–11 days, irrespective of harvest maturity or storage regime (Exp. 1). At 20 °C, peak CO2 production ranged from 90 to 137 ml kg−1 h−1 and peak ethylene production from 116 to 209 μl kg−1 h−1, respectively. Waxed fruit generally had higher CO2 and C2H4 production rates than unwaxed fruit. When LO fruit was stored continuously at 20 °C (Exp. 2), wax treatment alone hastened the onset of respiration and ethylene climacteric peaks by 5 days over unwaxed fruit. 1-MCP treatment alone delayed the onset of respiration and ethylene climacteric maxima by 6 and 5 days, respectively. Marketable life for wax-only fruit stored continuously at 20 °C was 10 days, while that for control, wax + 1-MCP and 1-MCP-only fruit was 13, 14, and 14 days, respectively. Mamey sapote fruit treated with wax lost less weight during continuous storage at 20 °C. At the full-ripe stage, no treatment effects were noted for pulp soluble solids content (23.4%) or pH (5.7). Mamey sapote fruit treated with wax + 1-MCP, however, retained total titratable acidity (0.25%) and lost less acid during storage than wax-only fruit (0.14%).

Ethylene Production throughout Growth and Development of Plants

Ethylene production by 10 or 20 m2 stands of wheat, soybean, lettuce, potato, and tomato was monitored throughout growth and development in an atmospherically closed plant chamber. Chamber ethylene levels varied among species and rose during periods of canopy expansion and rapid growth for all species. Following this, ethylene levels either declined during seed fill and maturation for wheat and soybean, or remained relatively constant for potato and tomato (during flowering and early fruit development). Lettuce plants were harvested during rapid growth and peak ethylene production. Chamber ethylene levels increased rapidly during tomato ripening, reaching concentrations about 10 times that measured during vegetative growth. The highest ethylene production rates during vegetative growth ranged from 1.6 to 2.5 nmol m-2 d-1 during rapid growth of lettuce and wheat stands, or about 0.3 to 0.5 nmol g-1 fresh weight per hour. Estimates of stand ethylene production during tomato ripening showed that rates reached 43 nmol m-2 d-1 in one study and 93 nmol m-2 d-1 in a second study with higher lighting, or about 50x that of the rate during vegetative growth of tomato. In a related test with potato, the photoperiod was extended from 12 to 24 hours (continuous light) at 58 days after planting (to increase tuber yield), but this change in the environment caused a sharp increase in ethylene production from the basal rate of 0.4 to 6.2 nmol m-2 d-1. Following this, the photoperiod was changed back to 12 h at 61 days and ethylene levels decreased. The results suggest three separate categories of ethylene production were observed with whole stands of plants: 1) production during rapid vegetative growth, 2) production during climacteric fruit ripening, and 3) production from environmental stress.

Effect of preharvest sprays containing calcium, magnesium and titanium on the quality of peaches and nectarines at harvest and during postharvest storage

AbstractPeach and nectarine trees were foliar sprayed with a formulation containing Ca2+, Mg2+ and Ti4+. Parameters related to fruit quality were evaluated at harvest, after 7–28 days of cold storage and after subsequent ripening for 4 days at 20 °C (shelf life). At harvest, treated fruits from both cultivars had higher weight and pulp firmness than control fruits, while no effect was observed for either colour, total soluble solid content (TSS) and titratable acidity (TA) or the time required to ripen on the tree. During cold storage, lower levels of weight loss, colour evolution, TSS/TA ratio and ethylene production and higher pulp firmness were found in treated peaches and nectarines compared with control fruits. Also, the storability of treated fruits was extended for up to 14 days more than that of control fruits. During ripening at 20 °C after different periods of cold storage, parameters related to ripening evolved faster in control than in treated fruits. Also, the occurrence of the climacteric peak of ethylene production was delayed and its intensity was lower in treated peaches and nectarines than in controls. Copyright © 2004 Society of Chemical Industry

Glucose Inhibits ACC Oxidase Activity and Ethylene Biosynthesis in Ripening Tomato Fruit

Experiments were carried out to evaluate the effect of glucose on ripening and ethylene biosynthesis in tomato fruit (Lycopersicon esculentum Mill.). Fruit at the light-red stage were vacuum infiltrated with glucose solutions post-harvest and changes in 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, ACC, ACC oxidase, and ethylene production monitored over time. ACC oxidase activity was also measured in pericarp discs from the same fruits that were treated either with glucose, fructose, mannose, or galactose. While control fruit displayed a typical peak of ethylene production, fruit treated with glucose did not. Glucose appeared to exert its effect on ethylene biosynthesis by suppressing ACC oxidase activity. Fructose, mannose, and galactose did not inhibit ACC oxidase activity in tomato pericarp discs. Glucose treatment inhibited ripening-associated colour development in whole fruit. The extent of inhibition of colour development was dependent upon the concentration of glucose. These results indicate that glucose may play an important role in ethylene-associated regulation of fruit ripening.

Ripening of ‘Hayward’ kiwifruit treated with 1-methylcyclopropene after cold storage

Abstract ‘Hayward’ kiwifruit [ Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var deliciosa ] were stored for 30 days at 0.5 °C and then treated with 0.5, 1 or 5 μl l −1 1-methylcyclopropene (1-MCP) for 16 h at 20 °C. Treated and control fruit were subsequently stored at 20±1 °C to ripen. Control fruit displayed a typical climacteric pattern of ethylene production. Peak ethylene production was measured at 17th day. Ethylene production by treated fruit remained low and they did not show an ethylene climacteric during 32 days of storage at 20 °C. Control fruit softened rapidly to 11.8 N in 4 days but fruit treated with 0.5 μl l −1 1-MCP did not soften to a similar extent until after 18 days. Treated fruit did not soften as much as control fruit but firmness of treated fruit after 32 days was considered appropriate for their consumption. Core tissue of 1-MCP treated fruit softened more slowly than outer cortical tissue. 1-MCP severely retarded changes in lightness and chroma in the outer cortex. Soluble solid concentrations (SSC) remained low in 1-MCP treated fruit for about 14 days. Fruit treated with 0.5 μl l −1 developed acceptable flavor and reached SSC similar to those in control fruit (15.3%) by 28 days. The increase of SSC in fruit treated with 5 μl l −1 1-MCP underwent further retardation. Activity of three glycosidases (β- d -galactosidase (β-Gal), α- l -arabinofuranosidase (α-Af), and β- d -xylosidase (β-Xyl)) increased in control fruit during ripening but only to a limited extent, or not at all, in fruit treated with 1 μl l −1 1-MCP.

Conservação pós-colheita de melões Galia 'Solar King' tratados com 1-metilciclopropreno

Avaliou-se o efeito de concentrações de 1-metilciclopropeno (1-MCP) sobre o amaciamento da polpa (através da firmeza e de tomografia de ressonância magnética), o desenvolvimento da região de abscisão do pedúnculo, o comportamento respiratório e a qualidade pós-colheita de melão Galia 'Solar King', em temperatura ambiente. Os frutos, provenientes do Polo Agrícola Mossoró-Assú (RN), foram colhidos com a região do pedúnculo ainda íntegra e tratados com solução contendo o fungicida Imazalil e a cera Megh Wash, ambos na concentração de 20 ml 10 L-1. Os frutos foram submetidos a tratamento com 1-MCP, nas concentrações 0; 100; 300 e 900 nl L-1, e ao armazenamento sob temperatura ambiente (24,5 ± 0,9ºC e 86,4 ± 7,9% UR), durante 0; 4; 8; 12; 16 e 20 dias. Utilizou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 4x6, com quatro repetições. O 1-MCP reduziu a atividade respiratória, atrasou o pico de produção de etileno e retardou a evolução do amaciamento da polpa e o desenvolvimento da região de abscisão do pedúnculo. Não foram verificados efeitos das concentrações testadas sobre a perda de massa, a acidez total titulável, o pH, o teor de sólidos solúveis totais, o teor de açúcares solúveis totais e a aparência externa. Contudo, a aparência interna dos frutos tratados foi melhor, principalmente naqueles expostos a 300 nl L-1. Esta concentração possibilitou, ainda, atividade respiratória mais baixa, frutos mais firmes e com menor desenvolvimento da região de abscisão peduncular.

Comportamento respiratório e qualidade pós-colheita de graviola (Annona muricata L.) 'morada' sob temperatura ambiente

Objetivou-se avaliar alterações físicas e físico-químicas, relacionando-as às taxas respiratória e de liberação de etileno, durante a maturação da graviola-'Morada'. Frutos colhidos na maturidade fisiológica foram armazenados (23,4 ± 1,1ºC e 81,8 ± 10,6% UR) e avaliados aos 0; 1; 2; 3; 4 e 6 dias, quanto a: atividade respiratória (RS), liberação de etileno (ET), perda de matéria fresca, cor da casca e da polpa, firmeza, pH, acidez total titulável (ATT), sólidos solúveis totais (SST) e açúcares solúveis totais (AST). Utilizou-se o delineamento experimental inteiramente casualizado, com quatro repetições. Aos dois dias, iniciou-se rápido aumento na RS, resultando no primeiro pico (197,60mg CO2·kg-1·h-1), que foi seguido por queda e uma fase lag. Ao término desta, iniciou-se o aumento climatérico (pico = 298,82mg CO2·kg-1·h-1). ET só foi detectada por ocasião do primeiro pico respiratório, atingindo o máximo aos quatro dias. A cor da casca tornou-se mais clara, enquanto na polpa se observou apenas redução da luminosidade. Houve coincidência entre o primeiro aumento na RS, o pico de ET e as mudanças mais significativas na firmeza, na ATT e nos teores de SST e AST. Durante o período, a firmeza diminuiu de 60 para 0,9N, e a ATT aumentou de 0,18 para 0,88% de ácido cítrico.

Respiration rate, ethylene production and biochemical changes during fruit development and maturation of jujube (Ziziphus mauritiana Lamk)

AbstractJujube fruits (Ziziphus mauritiana Lamk) of cv Zaytoni were harvested from fruit set until maturity to study some physiological and biochemical changes. Jujube fruit cv Zaytoni displayed a double‐sigmoid growth curve with a very short second stage (2 weeks). Changes in respiration rate and ethylene production during fruit development were typical of climacteric fruits, the peak of ethylene production coinciding with the climacteric rise in respiration. As for chemical constituents, reducing sugars were dominant and sucrose was absent in ripe fruit. Total soluble solid content was low during the early stages of growth, then increased to a peak in ripe fruit. Titratable acidity was low initially, but increased to a peak in physiologically mature fruit and declined rapidly in ripe fruit. The pattern of changes in protein content was typical of that characterising climacteric fruits.© 2002 Society of Chemical Industry

Differential Regulation of Genes Encoding Ethylene Biosynthesis Enzymes and Ethylene Response Sensor Ortholog during Ripening and in Response to Wounding in Avocados

We investigated the differential regulation of two 1-aminocyclopropane-1-carboxylate synthase (ACS) genes, one 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene and one ethylene response sensor (ERS1) ortholog during ripening and in response to wounding in avocados (Persea americana Mill. `Bacon'). The 1-aminocyclopropane-1-carboxylate (ACC) content, ACS activity and detectable expression of PA-ACS1 mRNA increased and reached a maximum prior to the climacteric peak, whereas ACO activity and the PA-ACO mRNA levels increased markedly only at the upsurge of ripening ethylene. A basal level of PA-ERS1 transcript was detected as from harvest, however, PA-ERS1 transcript was hyper-induced at the climacteric peak of ethylene production. 1-Methylcyclopropene (1-MCP) application at thepreclimacteric and the onset of climacteric stages inhibited the ACS and ACO activities, the transcription of PA-ACS1 and suppressed PA-ACO and PA-ERS1 mRNAs to trace levels. Discontinuation of 1-MCP treatment led to super-induction of PA-ACS1, PA-ACO, and PA-ERS1 transcripts. Wound induced ethylene biosynthesis and wound-induced PA-ACS2 mRNA accumulation were enhanced by 1-MCP, whereas wound-induced PA-ACO mRNA accumulation was unaffected by 1-MCP. These results indicate positive feedback regulation of the PA-ACS1 gene and negative feedback regulation of the PA-ACS2 gene by ethylene, while PA-ACO exhibits positive feedback regulation by ethylene and is also induced by wounding. The hyper-induction of PA-ERS1 mRNA at relatively high concentrations of ethylene may be a mechanism of avocados to regulate the ethylene responsiveness of the tissues by dissipation of the gas.

Fruit development and ripening in Barbados cherry, Malpighia emarginata DC.

Barbados cherry fruit shows a biphasic pattern of growth whether monitored on a diameter or weight basis. Each growth phase was of about 2 weeks duration with weight gains of equal magnitude but with most of the size increase occurring in the first phase. Pyrene growth paralleled that of the whole fruit. Cell division was limited to the first week of fruit development and horticultural maturity was reached when fruit showed colour break (18 days post-anthesis). Barbados cherry is climacteric with a very high peak respiratory rate (900 ml CO 2 kg −1 h −1) but a low rate of peak ethylene production (3 μl C 2H 4 kg −1 h −1), the former consistent with its high perishability.

Physicochemical Changes during Date Ripening Related to Ethylene Production

Some physicochemical parameters related to ripening and their relationship with ethylene were studied in date fruits ( Phoenix dactyliferaL. type Negros). Dates were harvested and classified into sixteen ripening stages according to their color, ranging from yellow-greenish to dark brown. Fruit firmness decreased through the different ripening stages, while the ripening index, expressed as the relation between soluble solids and acidity, increased. The greatest loss of fruit firmness correlated with the greatest increases in both polygalacturonase and •-galactosidase activities. In early ripening stages, a small peak in ethylene production was detected, followed by a peak in respiration rate, suggesting that a date could be considered as a climacteric fruit, with the plant hormone ethylene being responsible for changes in color, fruit firmness, soluble solids content and acidity.