Physiological aspects affected by photoselective nets in apples: Preliminary studies

Photoselective nets are an emerging technology that might affect apple tree productivity and fruit quality. However, the physiological aspects involved in these photo-responses are not yet fully understood. The aim of this research was to evaluate the effects of photoselective nets on apple leaf gas exchange. Two-year-old 'Fuji' apple trees grown in 40-L pots were covered with shade or hail nets, according to the following treatments: red shade net (RS), grey shade net (GS), blue shade net (BS), pearl hail net (PH), red hail net (RH). Light transmission (400-800 nm) spectra, leaf net photosynthesis (PN) and net transpiration (E) were measured under nets. Photosynthetically active radiation (400-700 nm) transmission was reduced 20.2% by RH, 12.5% by PH, 41.9% by RS, 46.3% by BS and 56.3% by GS. Spectral composition was unaltered by GS and PH nets, while RH, RS and BS substantially changed the blue:red light proportion. GS, RS and BS nets significantly increased E compared to RH and PH, while under BS, PN was significantly higher than RS, RH and PH. Differences on PN and E under photoselective nets are linked to changes in light quantity, but also in light quality, which probably affect anatomical and morphological aspects. These responses are currently being assessed.