Impact of exogenous silicon addition on chromium uptake, growth, mineral elements, oxidative stress, antioxidant capacity, and leaf and root structures in rice seedlings exposed to hexavalent chromium

Abstract

Hydroponic experiments were conducted to investigate the role of exogenous silicon (Si) addition in increasing hexavalent chromium (Cr VI) tolerance in rice seedlings. Rice seedlings were grown under 100 lM Cr(VI) stress without or with 10 lM Si. Chromium treatment decreased growth, photosynthetic pigments and protein, which was accompanied by a significant increase in Cr accumulation and lipid peroxidation (as malondialdehyde; MDA). However, Si addition alleviated Cr toxicity and promoted growth of rice by decreasing Cr accumulation, root-to-shoot Cr transport and MDA level. Contents of macro (Mg, Ca and K) as well as micronutrients (Zn and Fe) were decreased by Cr except Mn while Si addition prevented decrease in these nutrients induced by Cr. Antioxidant capacity and total phenolic contents were decreased by Cr while these indices improved by Si addition. Treatment of Cr decreased the length of leaf epidermal cells and stomatal frequency, and adversely affected chloroplasts containing mesophyll cells and integrity of xylem and phloem, and Si addition minimized these abnormalities. However, frequency of root hairs was increased by Cr treatment. Results showed that exogenous Si addition enhanced Cr(VI) tolerance in rice seedlings by decreasing Cr accumulation, root-to-shoot Cr transport and MDA level, and by increasing content of some mineral elements (K, Fe and Zn) and antioxidant capacity compared to the Cr treatment alone.

Biochemical Changes under Chromium Stress on Germinating Seedlings of <i>Vigna radiata</i>

“…Our results indicate that excessive heavy metal increases oxidative stress as it is evident from increased lipid peroxidation. It is in accordance with Ozdener et al (2011) and Tripathi et al (2012). SOD, CAT, GR, POX and APX are important components in preventing oxidative stress in plants by scavenging free radicals and peroxides with the elevation of their activities when exposed to heavy metal stress (Shanker et al, 2005).…”

“…Cr is known to induce production of elevated concentration of ROS resulted in macromolecule damage. Plants have evolved mechanisms to overcome ROS induced damage by accumulation of proline, ascorbate and glutathione and increasing the activities of SOD, CAT, GR, POX and APX (Samantaray et al, 1998;Nataraj et al, 2009, Thounaojam et al, 2012Tripathi et al 2012;). Antioxidants are the compounds, which act as osmotic buffers; beside this, they scavenge ROS (Nataraj and Paramar, 2008, Nataraj and Roshan, 2008, Nataraj et al, 2009.…”

Acquisition and Homeostasis of Iron in Higher Plants and Their Probable Role in Abiotic Stress Tolerance

“…Various techniques are being used to protect plants from the adverse effects of abiotic stresses, which include exogenous supplementations of silicon, nitric oxide, growth-promoting hormones, enzymes, and nutrient management (Nagajyoti et al, 2010;Nazar et al, 2012;Tripathi et al, 2012Tripathi et al, , 2016aTripathi et al, , 2017aVaculík et al, 2012;Saxena and Shekhawat, 2013). Among the remedies for abiotic stress, nutrient regulations or management are considered as the cost effective and eco-friendly techniques Yadav et al, 2016).…”

Silicon bioavailability in exocarp of Cucumis sativus Linn.

“…The availability of these elements may confirm the nutritional value and importance of cucumber fruit for the humans and animals. Moreover, these nutrient elements also have unique functions and their balanced availability is essential for the metabolic systems of all living organisms (Soetan et al 2010;Tripathi et al 2015a). Silicon provided tolerance, to plants form abiotic and biotic stresses, as it gives mechanical strength to plant tissues (Sangster et al 2001;Tripathi et al 2012aTripathi et al , b, 2014Tripathi et al , 2015b.…”