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Effetti dell’ozono sull’attività fotosintetica di piante di fagiolo esposte ad elevata intensità luminosa
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Effects of mild water stress on water balance and photosynthesis in soybean (Glycine max L.Merr.) plants
No full textUtilization of potassium from feldspar by sunflower plants under nitrogen deficiency conditions
No full textEffects 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
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