RESEARCH ARTICLE Promotive role of 5-aminolevulinic acid on chromium-induced morphological, photosynthetic, and oxidative changes in cauliflower (Brassica oleracea botrytis L.) Rehan Ahmad 1 & Shafaqat Ali 1 & Fakhir Hannan 1 & Muhammad Rizwan 1 & Muhammad Iqbal 1 & Zaidul Hassan 1 & Nudrat Aisha Akram 2 & Saliha Maqbool 3 & Farhat Abbas 1 Received: 20 December 2015 /Accepted: 7 February 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract Chromium (Cr) is among the most toxic pollutants in the environment that adversely affect the living organisms and physiological processes in different plants. The present study investigated the effect of 15 mg L - 1 of 5- aminolevulinic acid (ALA) on morpho-physiological attri- butes of cauliflower (Brassica oleracea botrytis L.) under dif- ferent Cr concentrations (0, 10, 100, and 200 μM) in the growth medium. The results showed that Cr stress decreased the growth, biomass, photosynthetic, and gas exchange pa- rameters. Chromium stress enhanced the activities of enzy- matic antioxidants, catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in response to oxidative stress caused by the elevated levels of malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ), and electrolyte leakage (EL) in both roots and leaves of cauliflower. Chromium concentra- tions and total Cr uptake were increased in leaves, stems, and roots with increasing Cr levels in the culture medium. Foliar application of ALA increased the plant growth param- eters, biomass, gas exchange parameters, and photosynthetic pigments under Cr stress compared to the treatments without ALA. Foliar application ALA decreased the levels of MDA, EL, and H 2 O 2 while further improved the performance of antioxidant in both leaves and roots compared to only Cr- stressed plant. Chromium concentrations and total Cr uptake were decreased by the ALA application compared to treat- ments without ALA application. The results of the present study indicated that foliar application of ALA might be bene- ficial in minimizing Cr uptake and its toxic effects in cauliflower. Keywords Cauliflower . Photosynthesis . Antioxidant enzymes . Chromium . Electrolyte leakage ALA . Hydrogen peroxide . Malondialdehyde Introduction Under natural conditions, agricultural crops are prone to nu- merous biotic and abiotic stresses such as heavy metals, dis- eases, drought, and salinity (Ahmad et al. 2014; Rizwan et al. 2015; Adrees et al. 2015a; Khan et al. 2016). Heavy metal (HM) toxicity in plants is the most widespread problem which not only limit the crop growth and yield but also enters in the system of humans and animals through the food chain (Liu et al. 2015; Khan et al. 2015a; Rizwan et al. 2016a). Chromium, (Cr) among HMs, mainly enters in the soil through anthropogenic activities (leather tanning, metallurgi- cal, etc.) and causes toxic effects on plant growth, develop- ment, and yield (Shakir et al. 2012; Khan et al. 2015b). The Cr concentration in soil may vary greatly depending on the com- position of natural rocks and sediments as well as anthropo- genic activities (Oliveira 2012; Singh et al. 2013). Many stud- ies have witnessed that Cr stress decreased the plant growth and yield, caused leaf chlorosis and root damage, and finally, resulted in plant death (Gill et al. 2015; Dheeba et al. 2015; Responsible editor: Yi-ping Chen * Muhammad Rizwan mrazi1532@yahoo.com 1 Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, Faisalabad 38000, Pakistan 2 Department of Botany, Government College University, Allama Iqbal Road, Faisalabad 38000, Pakistan 3 Department of Soil, Water, and Climate, University of Minnesota, 439 Borlaug Hall (map) 1991 Upper Buford Circle, St. Paul, MN 55108-6028, USA Environ Sci Pollut Res DOI 10.1007/s11356-017-8603-7