Role of organic and inorganic amendments on physiological attributes of germinating pea seedlings under arsenic stress

There are scarce data regarding the effects of soil amendments on biophysicochemical responses of plants at the early stages of growth/germination. This study critically compares the effects of ethylene-diamine-tetra-acetic-acid (EDTA) and calcium (Ca) on biophysicochemical responses of germinating pea seedlings under varied arsenic levels (As, 25, 125, 250 µM). Arsenic alone enhanced hydrogen peroxide (H2O2) level in pea roots (176%) and shoot (89%), which significantly reduced seed germination percentage, pigment contents, and growth parameters. Presence of EDTA and Ca in growth culture minimized the toxic effects of As on pea seedlings, EDTA being more pertinent than Ca. Both the amendments decreased H2O2 levels in pea tissues (16% in shoot and 13% in roots by EDTA, and 7% by Ca in shoot), and maintained seed germination, pigment contents, and growth parameters of peas close to those of the control treatment. The effects of all As-treatments were more pronounced in the pea roots than in the shoot. The presence of organic and inorganic amendments can play a useful role in alleviating As toxicity at the early stages of pea growth. The scarcity of data demands comparing plant biophysicochemical responses at different stages of plant growth (germinating vs mature) in future studies. Till date, abundant research has focused on plant biophysicochemical responses to different types of pollutants. However, the majority of these studies dealt with pollutant exposure to mature plants (generally after a vegetative growth period of 1–2 weeks). Despite significant research, there are still limited data regarding the biophysicochemical responses of plants at their early stages of germination and growth. In fact, stresses at germination or at an early stage of growth can be highly fatal and may significantly affect the ultimate plant growth and potential to remediate the contaminated sites. Therefore, the current study deals with the exposure of germinating pea seedlings to arsenic (As) stress under varied amendments. This experimental plan helped to understand the initial biophysicochemical changes induced in pea plants under As stress.</p

Arsenic(V) biosorption by charred orange peel in aqueous environments

<p>Biosorption efficiency of natural orange peel (NOP) and charred orange peel (COP) was examined for the immobilization of arsenate (As(V)) in aqueous environments using batch sorption experiments. Sorption experiments were carried out as a function of pH, time, initial As(V) concentration and biosorbent dose, using NOP and COP (pretreated with sulfuric acid). Arsenate sorption was found to be maximum at pH 6.5, with higher As(V) removal percentage (98%) by COP than NOP (68%) at 4 g L⁻¹ optimum biosorbent dose. Sorption isotherm data exhibited a higher As(V) sorption (60.9 mg g⁻¹) for COP than NOP (32.7 mg g⁻¹). Langmuir model provided the best fit to describe As(V) sorption. Fourier transform infrared spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy analyses revealed that the –OH, –COOH, and –N-H surface functional groups were involved in As(V) biosorption and the meso- to micro-porous structure of COP sequestered significantly (2-times) higher As(V) than NOP, respectively. Arsenate desorption from COP was found to be lower (10%) than NOP (26%) up to the third regeneration cycle. The results highlight that this method has a great potential to produce unique ‘charred’ materials from the widely available biowastes, with enhanced As(V) sorption properties.</p

Phosphate-assisted phytoremediation of arsenic by <i>Brassica napus</i> and <i>Brassica juncea</i>: Morphological and physiological response

<p>In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg⁻¹) on growth, gas exchange attributes, and photosynthetic pigments of <i>Brassica napus</i> and <i>Brassica juncea</i> under arsenic (As) stress (0, 25, 50, 75 mg kg⁻¹) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for <i>B. napus</i>, notably due to higher shoot As concentration and dry biomass yield, compared to <i>B. juncea</i> at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in <i>B. juncea</i>, it reduced shoot dry biomass, primarily after 50 and 75 mg kg⁻¹ As treatments. The translocation factor and bioconcentration factor values of <i>B. napus</i> were higher than <i>B. juncea</i> for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for <i>B. napus</i>, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.</p