Photo-selective colored nets have been used as a tool to reduce climatic stress and improve yields in horticultural crops, but there is no knowledge regarding responses of hazelnut crops under these nets. The objective of this research was to study the influence of photo-selective nets on the microclimate, physiological characteristics of leaves, and yield in hazelnut. During three consecutive seasons, a hazelnut orchard ´Tonda di Giffoni´ was covered with black, blue-gray, and pearl-gray colored nets with a standard density of 4 warp and weft threads cm⁻¹. Uncovered trees were used as the control. Microclimatic conditions (solar radiation intensity and composition, air temperature, relative humidity, and vapor pressure deficit, VPD), yield components (accumulated yield; yield by harvest date; fruit weight, FW; and seed weight, SW), and leaf physiological characteristics (net photosynthesis rate, A_n; stomatal conductance, g_s; specific leaf weight, SLW; and stomatal density, SD) were evaluated. Pearl-gray netting had the greatest increase in diffuse (47%) and global (5%) solar radiation compared to blue-gray and black nettings. VPD decreased by 12% under black netting, but only by 5% under pearl-gray and blue-gray netting. Pearl-gray nets significantly increased accumulated yield, FW, and SW by 12, 13, and 6% compared to the control, respectively. Black and blue-gray nets reduced SD by 8 and 30% and SLW by 15 and 20%, respectively. Pearl-gray netting did not alter either SD or SLW. A significant relationship between A_n and g_s was found under all nets, but not for the control. The relationship between A_n and g_s was significantly positive for pearl-gray netting and negative for blue-gray netting. Photo-selective netting is a physiology-based tool that improves yield in hazelnut orchards under extreme climate conditions. Pearl-gray netting is the most promising alternative for this fruit crop.

光选择性彩色网已被用作减少气候压力和提高园艺作物产量的工具，但尚不清楚这些网对榛子作物的反应。本研究的目的是研究光选择性网对榛子小气候、叶片生理特性和产量的影响。在连续三个季节中，榛子园 'Tonda di Giffoni' 覆盖着黑色、蓝灰色和珍珠灰色的网，标准密度为 4 根经纬线 cm ^-1. 未覆盖的树木用作对照。小气候条件（太阳辐射强度和成分、气温、相对湿度和蒸汽压差，VPD）、产量构成（累积产量；按收获日期划分的产量；果实重量，FW；和种子重量，SW）和叶片生理特征（净光合速率，A _n；气孔导度，g _s; 比叶重，SLW；和气孔密度，SD）进行了评估。与蓝灰色和黑色网相比，珍珠灰色网的漫射 (47%) 和全球 (5%) 太阳辐射增幅最大。VPD 在黑网下下降了 12%，但在珍珠灰色和蓝灰色网下仅下降了 5%。与对照相比，珍珠灰色网使累积产量、FW 和 SW 分别显着增加了 12%、13% 和 6%。黑色和蓝灰色网分别将 SD 降低了 8% 和 30%，SLW 降低了 15% 和 20%。珍珠灰色网没有改变 SD 或 SLW。在所有网络下都发现了A _n和g _s之间的显着关系，但在对照中则不然。A _n和g _s之间的关系对珍珠灰色网呈显着阳性，对蓝灰色网呈阴性。光选择性网是一种基于生理学的工具，可在极端气候条件下提高榛子园的产量。珍珠灰色网是这种水果作物最有前途的替代品。