1,720,966 research outputs found
Effects of elevated ozone on chlorophyll a fluorescence in symptomatic and asymptomatic leaves of two tomato genotypes
No full textTwo different genotypes of Lycopersicon esculentum Mill. (cv. Cuor di Bue, O3-sensitive and line 93.1033/1,
O3-resistant) were treated with a single dose of ozone (150 mm3 m-3 for 3 h). The PS 2 activity was examined by
measurements of chlorophyll a fluorescence on symptomatic and asymptomatic leaves. Symptoms were evident on the
4th leaves from the bottom, in both genotypes, while the 2nd leaves of the line 93.1033/1 were asymptomatic. In these
leaves, the net photosynthetic rate (PN) did not change even if the Fv/Fm ratio significantly decreased. A strong reduction
in PN, mostly due to the stomatal closure, was observed in Cuor di Bue. The non photochemical quenching coefficient
(qNP) and the degree of PS 2 reaction centres closure (1-qP) were higher, while the quantum efficiency of PS 2
photochemistry (ΦPS2) and quantum efficiency of excitation energy capture (Φexc.) were lower in O3 treated leaves of
both genotypes. The limitation of photosynthesis was shown also by a decrease in the parameter %P, which diminished
compared to controls in both genotypes. The response of the two genotypes for the energy fraction dissipated as thermal
energy in the PS 2 antennae (%D) was similar. The fraction of %P remained lower during the recovery in symptomatic
leaves of the resistant line as compared to the controls, whereas %X, which represents the amount of light energy that is
not utilized in photochemistry or dissipated in the PS 2 antennae, significantly rose in the asymptomatic leaves of this
line and in both the leaves of Cuor di Bue. From data obtained we concluded that ozone affected the plants
independently on the appearance of visible symptoms of injury because the leaves without visible symptoms of both the
genotypes were negatively influenced
Attività di alcuni enzimi del metabolismo dei fenilpropanoidi in foglie di Passiflora incarnata L. coltivata in vivo o in vitro
No full textNel lavoro vengono studiate le attività di alcuni enzimi coinvolti
nel metabolismo dei fenilpropanoidi, come la scichimato deidrogenasi
(SKDH), la fenilalanina ammonio liasi (PAL) e la calcone isomerasi
(CHI) in tessuti fogliari di piante di P. incarnata coltivate in vaso o in
vitro. Nelle piante allevate in vaso l’età della foglia determinava
variazioni significative nell’attività della PAL e CHI, con valori
elevati nelle foglie completamente espanse. Anche nelle piante
coltivate in vitro sono state evidenziate differenze in relazione alla
tecnica di coltivazione: le piante in eterotrofia presentavano valori di
attività di PAL, SKDH e CHI più elevati rispetto a quelle coltivate in
autotrofia
Proprietà nutraceutiche di ortaggi e frutta: influenza della coltivazione e della conservazione
No full textOzone tolerance in Phaseolus vulgaris depends on more than one mechanism
No full textTwo bean cultivars with different ozone-sensitivity, i.e. the O3-sensitive Cannellino and the O3-tolerant Top Crop, were exposed to acute O3-stress with the aim of evaluating physiological and biochemical traits responsible for O3-tolerance. The cultivars differed in their constitutive ability to prevent and counter O3-induced oxidative damage. The ability to dissipate excess-energy, via regulated and unregulated nonphotochemical quenching mechanisms (NPQ, NO) was constitutively greater in Top Crop than in Cannellino, and allowed the O3-tolerant cultivar to compensate light-induced declines in PSII and preserve photosystem II from excitation-energy to a superior degree than the O3-sensitive one. The inevitable generation of reactive oxygen species was countered to a significantly smaller extent in the O3-sensitive cultivar, because of constitutively lower activities of superoxide dismutase and catalase than the O3-tolerant cultivar. Indeed, Cannellino underwent an early accumulation of H2O2 and an almost complete disruption of cell structure and irreversible damages in the photosynthetic apparatus
Different sensitivity to browning in fresh-cut pineapple, apple and pear: the role of endogenous vitamin C
No full textPineapple, apple and pear were studied as fresh-cut fruit compared to the whole ones upon storage
at 4°C. Pineapple did not show any symptom related to enzymatic browning even after 216 h
of storage, in comparison symptoms were evident in apple and pear as soon as 24 h after cutting.
The different sensitivity of the three types of fruit was linked to the high content in ascorbic acid
in pineapple as compared to apple and pear
Physiological basis of sensitivity to enzymatic browning in 'lettuce', 'escarole' and 'rocket salad' when stored as fresh-cut products
No full textIn fresh-cut leafy vegetables, the operation of cutting may stimulate enzymatic browning, with important commercial consequences. In this work, a number of physiological and biochemical parameters, including the activities of key enzymes involved in the metabolism of phenols (such as PAL, PPO, and PODs) and ascorbic acid (ASA), were measured in three species: lettuce (Lactuca sativa var. capitata. L.), escarole (Cichorium indivia var. latifolium) and rocket salad (Eruca sativa), upon cold storage as fresh cuts. The first two species are quite sensitive to leaf browning, which does not affect rocket salad. The resistance of rocket salad to browning was associated with a much higher ASA content and a decrease in this compound upon storage, compared to other species in which ASA remained either constant (lettuce) or increased (escarole). It is proposed that the esistance
of rocket salad to this disorder, which markedly affects other leafy species, e.g., lettuce and escarole, is a result of the inhibition of PPO activity and/or the reduction of quinones to phenols, which may both be induced by ASA
Studio della fluorescenza della clorofilla a e dell’immagine della fluorescenza in due varietà di Lycopersicon esculentum sottoposte ad un singolo pulse di ozono
No full textBiochemical aspects in two minimally processed lettuces upon storage
No full textThe browning process was studied in two cultivars of minimally processed lettuce (Lactuca sativa var. capitata cv. Verpia and Lactuca sativa var. acephala cv. Lollo Rossa). The analyses were carried out upon storage at 4 C in the dark. The first interesting result was the resistance to browning of excised leaves of Lollo Rossa, that did not present the typical symptoms of browning. Another important characteristic of Lollo Rossa lettuce was the higher antioxidant ability before storage. The results of biochemical characteristics obtained in this experiment did not show clear evidence supporting the biochemical model of tissue browning involving the sequential synthesis of phenolics and quinones that are regulated, respectively, by phenyl alanine ammonia-lyase, polyphenol oxidase and/or peroxidase
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