Climate Stressors on Growth, Yield, and Functional Biochemistry of two Brassica Species, Kale and Mustard

Due to climate change, the attainment of global food security is facing serious challenges in meeting the growing food demand. Abiotic stresses are the foremost limiting factors for agricultural productivity. However, not much information is available on the effect of multiple abiotic stresses on the morphological and biochemical aspects of kale and mustard. Therefore, an experiment was designed to study the effects of UV-B radiation, CO₂ concentration, and high temperature on the growth, yield, and biochemistry of two Brassica species, namely B. oleracea L. var. acephala Winterbor F1 (hybrid kale) and B. juncea var. Green wave O.G. (mustard greens), which were grown under optimal nutrients and soil moisture conditions in soil-plant-atmosphere-research (SPAR) units. Two levels of UV-B radiation (0 and 10 kJ m^-2 d^-1), two concentrations of CO₂ (420 and 720 ppm), and two different temperature treatments (25/17 °C and 35/27 °C) were imposed 12 days after sowing (DAS). Several morphological and biochemical parameters were measured at harvest (40 DAS) in both species. All the traits declined considerably under individual and multi-stress conditions in both species except under elevated CO₂ levels, which had a positive impact. Marketable fresh weight decreased by 64% and 58% in kale and mustard plants, respectively, growing under UV-B treatment. A slight increase in the chlorophyll content was observed in both species under the UV-B treatment alone and in combination with high temperature and elevated CO₂. Understanding the impacts of high temperature, CO₂, and UV-B radiation treatments on leafy vegetables, such as kale and mustard, can help to improve existing varieties to enhance resilience towards environmental stresses while simultaneously improving yield, morphology, and biochemistry in plants.