Respiratory metabolism in the embryonic axis of germinating pea seed exposed to cadmium

• Published in: Journal of plant physiology Vol. 166; no. 3; pp. 259 - 269
• Main Authors: Smiri, Moêz, Chaoui, Abdelilah, El Ferjani, Ezzedine
• Format: Journal Article
• Language: English
• Published: Munich Elsevier GmbH 01.01.2009; Elsevier
• Subjects: Biological and medical sciences; Biomass; Cadmium; Cadmium - toxicity; carbohydrate content; Carbohydrate Metabolism - drug effects; cell respiration; Cell Respiration - drug effects; Cotyledon - drug effects; Cotyledon - enzymology; electron transport chain; embryo (plant); enzyme activity; Fundamental and applied biological sciences. Psychology; Germination; Germination - drug effects; heavy metals; mineral content; mitochondria; Mitochondria - drug effects; Mitochondria - metabolism; peas; pentose phosphate cycle; phytotoxicity; Pisum sativum; Pisum sativum - cytology; Pisum sativum - embryology; Pisum sativum - enzymology; Pisum sativum - metabolism; Plant physiology and development; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Respiration; seed germination; Seeds - drug effects; Seeds - enzymology; Seeds - metabolism; Solubility - drug effects; tricarboxylic acid cycle; NCCR; Cadmium; ADH; INV-NS; Germination; G6PDH; INADH; INV-AS; CCO; 6PGDH; MDH; Pisum sativum; INV-AW; SDH; SCCR; Respiration; Seeds; Metabolism; Grain legume; Leguminosae; Plant physiology; Dicotyledones; Angiospermae; High protein crop; Spermatophyta; Embryonic axis
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2008.05.006

Seeds of pea ( Pisum sativum L.) were germinated for 5 d by soaking in distilled water or 5 mM cadmium nitrate. The relationships among cadmium stress, germination rate, changes in respiratory enzyme activities and carbohydrates mobilization were studied. Two cell fractions were obtained from embryonic axis: (1) mitochondria, used to determine enzyme activities of citric acid cycle and electron transport chain, and (2) soluble, to measure some enzyme activities involved in fermentation and pentose phosphate pathway. Activities of malate- and succinate-dehydrogenases (MDH, SDH) and NADH- and succinate-cytochrome c reductases (NCCR, SCCR) were rapidly inhibited, while cytochrome c oxidase (CCO) was unaltered by cadmium treatment. However, this stimulated the NADPH-generating enzyme activities of the pentose phosphate pathway, glucose-6-phosphate- and 6-phosphogluconate-dehydrogenases (G6PDH, 6PGDH), as well as enzyme activity of fermentation, alcohol dehydrogenase (ADH), with concomitant inhibition in the capacity of enzyme inactivator (INADH). Moreover, Cd restricted carbohydrate mobilization in the embryonic axis. Almost no glucose and less than 7% of control fructose and total soluble sugars were available in the embryo tissues after 5 d of exposure to cadmium. Cotyledonary invertase isoenzyme activity was also inhibited by Cd. The results indicate that cadmium induces disorder in the resumption of respiration in germinating pea seeds. The contribution of Cd-stimulated alternative metabolic pathways to compensate for the failure in mitochondrial respiration is discussed in relation to the delay in seed germination and embryonic axis growth.