|Authors: ||E.J. Fernandez-Rodriguez, D. Perez, F. Camacho-Ferre, J. Fernandez Vadillos, A. Kenig|
|Keywords: ||photosystem II, fluorescence, photoinhibition|
The effects on photochemical efficiency of three different moveable shading screens of a commercial aluminized type (40%, 50% and 60% ALUMINET ®) vs a typical whitewash installed under a modern `raspa´ and `amagado´ tomato greenhouse at Almeria were studied during six different dates in a single growing season.
Fluorescence characteristics were measured using a modulated fluorimeter (Hansatech Electronics Ltd.
U.K). Measurements were taken during periods of 2 or 3 days each, with 5 to 7 daily measurements.
Differences were found between shading screens and whitewash during different schedules of operation.
It was found a protective effect under aluminized treatments when screens were used for energy saving (in the night-time hours) specially during the period of lower temperatures.
Differences could be related to higher leaf temperatures as a result of higher air temperature under screens.
When screens were used for heat stress prevention (4th, 5th and 6th cycles) Fv/Fm daily pattern showed clear differences in the mid-day hours between plants under aluminized screens and plants under whitewash.
However the increase in shading density was not directly proportional to reduction in photoinhibition in the screens tested.
Under low wind speed conditions screen density could limit ventilation rates.
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