Growing under photoselective nets affects the gas exchange and chemical composition of the leaves of highbush blueberry (Vaccinium corymbosum L.) before and after harvest

The use of photoselective nets in highbush blueberry (Vaccinium corymbosum L.) orchards could affect the light properties below the nets, along with the plants' physiological processes and the chemical composition of their leaves. In our research, we compared the effects of black, red, yellow, and white exclusion nets with full-sun conditions (control) on light quality and quantity and the performance of blueberry 'Bluecrop' leaves over two consecutive years. The light properties were found to be altered by the nets. The net photosynthesis and leaf gas exchange did not differ among the treatments in 2022. In 2023, the lowest net photosynthesis was measured in the leaves of plants under the control treatment (7.08 mu mol m_ 2 s_ 1) before harvest and under the black (3.01 mu mol m_ 2 s_ 1) and red nets (3.36 mu mol m_ 2 s_ 1) after harvest. At the same time, plants without fruit exhibited significantly lower values of carbon assimilation. The highest chlorophyll fluorescence value was measured in the plants under the red net (0.59) before harvest and under the white exclusion net (0.40) after harvest. Among the measured chloroplast pigments, zeaxanthin increased under the yellow net and the control treatment in 2022, while in 2023, it increased under the red net, white exclusion net, and control treatment before harvest. The total phenolics differed significantly among the treatments across all three sampling dates, with the highest contents measured before harvest in 2023. These promising results indicate that other blueberry cultivars and colored photoselective nets should also be examined in future experiments.