Drought tolerance in Zn-deficient red cabbage (Brassica oleracea L. var. capitata f. rubra) plants

Effects of Zn deficiency were studied in red cabbage plants under well-watered or drought conditions. Impairment of growth due to Zn deficiency was higher under drought compared with well-watered conditions. Drought stress caused a drastic decline in Zn content and led to a damage of photosynthetic apparatus in Zn-deficient but not Zn-sufficient leaves. Net assimilation and transpiration rate were strongly reduced under Zn deficiency and drought conditions following reduction of stomatal conductance. Activity of antioxidant enzymes, with the exception of superoxide dismutase, increased under Zn deficiency conditions, while drought enhanced activity of all studied enzymes concomitant with accumulation of malondialdehyde and H2O2. The intensifying effect of drought on Zn-deficient leaves could be explained by impaired leaf photochemical events, reduction of whole plant photosynthesis and imbalance between production and scavenging of reactive oxygen species. Water use efficiency, water and osmotic potential of drought-stressed plants were higher under low compared with adequate Zn supply, however, these parameters were not critical for plant growth response under combinative effect of drought and Zn deficiency.