Studies on chinese leafy cabbage response to photoperiod

Abstract

Background. In controlled-environment vegetable production, photoperiod is a key driver of plant growth and yield. The purpose of the study is to quantify photoperiodic responses in two Chinese leafy cabbage cultivars (Lastochka and Vesnyanka) under the same light spectrum and photon flux density. Materials and methods. Plants were grown in a controlled- climate chamber on a peat-based substrate. Photoperiod treatments were 8, 12, 16, and 20 h at a photon flux density of 220 μmol·m⁻²·s⁻¹ under controlled temperatures. We measured leaf number, fresh and dry biomass, leaf area, and leaf mass per area, as well as leaf gas exchange and chlorophyll fluorescence traits. Results. Leaf number increased with photoperiod and peaked at 20 h (10.3 in Lastochka and 9.7 in Vesnyanka). Fresh biomass in Lastochka was maximal at 12 h (49.1 g), whereas Vesnyanka continued to increase up to 20 h (54.7 g). Vesnyanka showed the largest leaf area at 16–20 h (up to 1021 cm²), while Lastochka peaked at 12 h (755 cm²). The highest net photosynthesis rate occurred at 20 h (7.3 and 4.3 μmol·m⁻²·s⁻¹ for Lastochka and Vesnyanka, respectively). Conclusions. A 16–20 h photoperiod at 220 μmol·m⁻²·s⁻¹ is recommended for Chinese leafy cabbage in light culture; Vesnyanka exhibits higher tolerance to extended daily illumination.