Individual and Interactive Effects of Multiple Abiotic Stress Treatments on Early-Season Growth and Development of Two Brassica Species

Potential global climate change-related impacts on crop production have emerged as a major research priority and societal concern during the past decade. Future changes, natural and human-induced, projected in the climate have implications for regional and global crop production. The simultaneous occurrence of several abiotic stresses instead of stress conditions is most detrimental to crops, and this has been long known by farmers and breeders. The green leafy vegetables of the Brassicaceae family have especially gained attention due to their many health benefits. However, little information is available about abiotic stress’s effects on Brassica vegetables’ growth and development. An experiment was conducted on two Brassica species: B. oleracea L. var. acephala WINTERBOR F1 (hybrid kale) and B. juncea var. GREEN WAVE OG (mustard greens). Seven treatments were imposed on the two brassica species in soil–plant–atmosphere–research (SPAR) units under optimum moisture and nutrient conditions, including a control treatment (optimal temperature and UV-B conditions at ambient CO₂ levels), and six treatments where stresses were elevated: CO₂, UV-B, temperature (T), CO₂ +UV-B, CO₂ +T, and CO₂ +UV-B+T. Above-and below-ground growth parameters were assessed at 26 d after sowing. Several shoot and root morphological and developmental traits were evaluated under all the treatments. The measured growth and development traits declined significantly under individual stresses and under the interaction of these stresses in both the species, except under elevated CO₂ treatment. All the traits showed maximum reductions under high IV-B levels in both species. Leaf area showed 78% and 72% reductions, and stem dry weight decreased by 73% and 81% in kale and mustard, respectively, under high UV-B levels. The increased CO₂ concentrations alleviated some deleterious impacts of high temperature and UV-B stresses. The results of our current study will improve our understanding of the adverse effects of environmental stresses on the early-season growth and development of two Brassica species.