Cadmium stress affects seed germination and seedling growth in Sorghum bicolor (L.) Moench by changing the activities of hydrolyzing enzymes

Abstract

Seed germination, one of the most important phases in the life cycle of a plant, is highly responsive to existing environment. Hydrolyzing enzymes play a major role in the mobilization of food reserves by hydrolyzing carbohydrates, proteins and fats. This paper reports on the effect of Cd toxicity on seed germination and the activities of hydrolyzing enzymes, like acid phosphatases (ACPs), proteases and a-amylases in Sorghum bicolor (L.) Moench. The metal uptake by embryonic axes and seeds was quantified. We found that sorghum could tolerate up to 0.5 mM Cd. At concentrations above 3.0 mM, seed germination was adversely affected with a complete cessation of seedling growth. All investigated hydrolyzing enzymes exhibited a significant decrease in activity with increasing Cd concentrations. The isozyme profiles indicated the loss of one or two isozymes of ACP, induction of a new isozyme for total protease (at 3.0 mM Cd) and a decline in the intensity of aamylase isozymes. SEM studies revealed that Cd affected a change in root hair density. SEM investigations also confirmed the assay results of the inhibition of starch mobilization from endosperm. This suggested an inhibition of the hydrolysis of reserve carbohydrates and translocation of hydrolyzed sugars, ultimately resulting in decreased germination and disruption of seedling growth. Because sorghum is an important dryland crop, its response to the presence of Cd in agro-ecosystems and Cd-induced phytotoxicity during seed germination and seedling growth needs critical investigation.

Proteolytic activities in Phaseolus vulgaris cotyledons under copper stress

“…At day 9, the inhibition by copper treatment was approximately 60 %, compared to control. This finding corroborates numerous reports that heavy metals cause a decrease in protease activity; Cd (Bishnoi et al 1993;Shah and Dubey 1997;Kuriakose and Prasad 2008), Pb (Mohan and Hosetti 1997) and Ni (Maheshwari and Dubey 2007). The inhibition could not be explained only by the direct effect of the metal ion on the enzymatic proteins, since ACA was reduced less than 20 % after Cu incubation in vitro with the control enzymatic extract (9 days of H 2 Ogermination; Fig.…”

Effect of exogenous lead on growth and carbon metabolism of pea (Pisum sativum L) seedlings

“…Earlier it has been reported that higher levels of Pb inhibited the growth of higher plants such as vegetable crops (Moftah 2000) and corn seedlings (Malkowski et al 2002). Reduced seedling growth under heavy metal toxicity had also been correlated with decreased water absorption (Devi et al 2007;Kuriakose and Prasad 2008). In cotyledons of control seedlings, total sugars and sucrose content decreased with the progress of seedling growth indicating that sucrose is rapidly transported to growing shoots and roots and is not accumulated in the cotyledons.…”

Up-regulation of antioxidant and glyoxalase systems by exogenous glycinebetaine and proline in mung bean confer tolerance to cadmium stress

“…For Cd stress, seedlings were treated with Hyponex solution that contained 1 mM CdCl 2 in Petri plates lined with 4 layers of filter paper under the above conditions for 48 h. For Cd treatment in the presence of proline or betaine, seedlings were treated with 5 mM proline or 5 mM betaine with the above levels of CdCl 2 in Hyponex solution for 48 h. Control plants were grown in Hyponex solution only. In case of heavy metals, due to high binding capacity of filter paper to cations (Haluskova et al 2009;Tamás et al 2008;Kuriakose and Prasad 2008), application of 1 mM CdCl 2 concentration was required to obtain meaningful differences among the metabolites and the enzymatic activities within short period of time (48 h). Since the primary objectives of this investigation was to study the response of seedlings to Cd toxicity as well as biochemical mechanisms of proline-and betaine-induced Cd stress tolerance, these high concentrations were used throughout the experiment.…”