Abstract
Lead (Pb) is a widely spread pollutant and leads to diverse morphological and structural changes in the plants. In this study, alleviating role of 5-aminolevulinic acid (ALA) in oilseed rape (Brassica napus L.) was investigated with or without foliar application of ALA (25 mg L−1) in hydroponic environment under different Pb levels (0, 100, and 400 µM). Outcomes stated that plant morphology and photosynthetic attributes were reduced under the application of Pb alone. However, ALA application significantly increased the plant growth and photosynthetic parameters under Pb toxicity. Moreover, ALA also lowered the Pb concentration in shoots and roots under Pb toxicity. The microscopic studies depicted that exogenously applied ALA ameliorated the Pb stress and significantly improved the cell ultrastructures. After application of ALA under Pb stress, mesophyll cell had well-developed nucleus and chloroplast having a number of starch granules. Moreover, micrographs illustrated that root tip cell contained well-developed nucleus, a number of mitochondria, and golgi bodies. These results proposed that under 15-day Pb-induced stress, ALA improved the plant growth, chlorophyll content, photosynthetic parameters, and ultrastructural modifications in leaf mesophyll and root tip cells of the B. napus plants.
Highlights
Environmental pollutants like heavy metals are toxic even at low concentration
Plant growth retardation under Pb stress may be due to nutrient imbalance, disturbed photosynthesis, obstacle in electron transport system, and inadequate levels of carbon dioxide due to stomatal closure [5, 6]
The results showed that Pb toxicity significantly inhibited the plant growth as compared
Summary
Lead (Pb) is amongst one of the most toxic pollutants which is not an essential nutrient for plants [1]. Lead accumulation is recognized to cause highly deleterious effects on growth and yield of plants [3]. Plant growth retardation under Pb stress may be due to nutrient imbalance, disturbed photosynthesis, obstacle in electron transport system, and inadequate levels of carbon dioxide due to stomatal closure [5, 6]. It is documented that Pb prohibits the nutrient uptake, net photosynthetic rate, and cellular respiration and causes damage to cell membrane [7]. Jiang and Liu [9] proposed that exposure of Pb for 72 hr to Allium sativum roots induced ultrastructural changes, that is, loss of cristae, mitochondrial swelling, dictyosomes, endoplasmic reticulum vacuolization, impairment into lamellar organization of the chloroplast, and cell division [10]. It is very important to exploit the potential of oilseed rape plant against Pb stress
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