Application

UV-A screening (Apparent Transmittance at 365 nm). UV-A screening was most efficient (10%) on the upper side of field-grown leaves but it was virtually absent on the lower side of greenhouse-grown leaves. (Turn back for experimental information.)

Maximum photochemical quantum yield of photosystem II, FV/FM. The largest FV/FM was measures on the upper side of field-grown leaves, the smallest FV/FM had the lower side of greenhouse-grown leaves. The data is in agreement with Wientjes et al. (2013) J Phys Chem B 117: 11200−11208 who have ascribed high FV/FM to acclimation to high light intensities of the light harvesting antenna of photosystem II. (Turn back for experimental information.)

Total chlorophyll concentration (Chl a + Chl b) is higher in field-grown leaves compared to greenhouse-grown leaves.
(Turn back for experimental information.)

Light spectra measured at noon in the greenhouse (green line) and in the field (dark yellow). The ratio spectrum “Greenhouse/Field” (black line) dropped from roughly 0.3 at 500 nm to about 0.15 at 400 nm. This drop is due absorption of blue light by the greenhouse, which becomes prominent in the UV range. Spectra were recorded with a Miniature Spectrometer MINI-SPEC/MP (see MINI-PAM-II, Accessories).