An energy-saving glasshouse film reduces seasonal, and cultivar dependent Capsicum yield due to light limited photosynthesis

Glasshouse films can be used to reduce energy costs by limiting non-productive heat-generating radiation, but the impact on yield of greenhouse horticultural crops remains unknown. The effects of energy-saving film ULR-80 (referred to as Smart Glass; SG) designed to block long wavelength light that generates heat also reduced photosynthetically active radiation (PAR) consequently affecting crop morphology, photosynthesis, leaf pigments, and yield of two hydroponically grown capsicum ( Capsicum annuum L.) cultivars (Red and Orange). The crops were grown in four high-tech glasshouse bays over two seasons of similar daily light integrals (DLI) during ascending (Autumn) and descending (Summer) photoperiods. The Red cultivar exhibited higher photosynthetic rates (light saturated - A sat and maximal - A max ) and yield than the Orange cultivar in control but displayed stronger reductions in modelled photosynthetic rates at growth light and yield in SG without changes in photosynthetic capacity. Foliar pigment ratios of chlorophyll a/b and carotenoid: chlorophyll remained unaffected by the SG during both seasons indicating that chloroplast homeostasis was similar between SG and control. The seasonal differences in photosynthetic pigments and xanthophyll de-epoxidation state (DPS) revealed that cultivars were able to sense the SG-altered light environment during the ascending, but not descending photoperiod. The descending photoperiod correlated with a lower daily light level and a substantial yield reduction of 29 % and 13 % in Red and Orange cultivars, respectively. Thus, SG-induced higher reductions in yield during the descending photoperiod indicate that SG may be more beneficial for capsicum crops planted during Autumn with an ascending photoperiod. Highlights A potential energy saving SG film limited net photosynthesis of capsicum The SG film reduced yield of two capsicum cultivars that can be mitigated by planting during the low light growth season with a shorter photoperiod SG reduced genotype-dependent capsicum yield was associated with alterations in the level of foliar pigments required for photoprotection under adverse light conditions