Photosynthetic performance of Salvinia natans exposed to chromium and zinc rich wastewater

Abstract

Investigations were carried out to evaluate alterations in photosynthetic performance of Salvinia natans (L.) exposed to chromium (Cr) and zinc (Zn) rich wastewater. Accumulation of high levels of Cr and Zn in plants affected photosynthetic electron transport. Photosystem-(PS) II-mediated electron transport was enhanced in plants exposed to Cr rich wastewater while a decline was observed in Zn-exposed plants. Photosystem-I-mediated electron transport increased in plants exposed to Cr and Zn rich wastewater. Efficiency of photosystem II (F v /F m ) measured by fluorescence did not show any significant change in Cr-exposed plants but a decrease was observed in Zn-exposed plants as compared to the control. The enhancement in PS I-induced cyclic electron transport in Cr and Zn exposed plants led to a build up of the transthylakoidal proton gradient (∆pH) which subsequently helped in maintaining the photophosphorylation potential to meet the additional requirement of ATP under stress. The carbon assimilation potential was adversely affected as evident from the decrease in Rubisco (EC 4.1.1.39) activity. The alterations in photosynthetic electron transport affected stromal redox status and induced variations in the level of stromal components such as pyridine nucleotides in plants exposed to Cr and Zn rich wastewater. The present investigations revealed that alteration in the photosynthetic efficiency of Salvinia exposed to Cr could primarily be the result of a decline in carbon assimilation efficiency relative to light-mediated photosynthetic electron transport, though in the case of Zn-exposed plants both these factors were affected equally. Key words: carbon assimilation, electron transport, heavy metals, photophosphorylation, redox status Desempenho fotossintético de plantas de Salvinia natans expostas a água de esgoto rica em cromo e zinco: Avaliou-se o desempenho fotossintético de plantas de Salvinia natans L. expostas a água de esgoto rica em cromo (Cr) e zinco (Zn). O acúmulo de Cr e Zn em altos níveis afetou o transporte fotossintético de elétrons. O transporte de elétrons mediado pelo fotossistema (FS) II aumentou nas plantas expostas ao esgoto rico em Cr, observando-se o oposto nas plantas expostas ao esgoto rico em Zn. O transporte de elétrons mediado pelo FS I aumentou nas plantas expostas ao esgoto rico tanto em Cr como em Zn. A eficiência do FS II (F v /F m ) avaliada por fluorescência não variou significativamente em resposta ao Cr, porém reduziu-se nas plantas expostas ao esgoto rico em Zn, em comparação com as plantas-controle. O aumento do transporte cíclico de elétrons associado ao FS I acarretou em aumento do gradiente transtilacoidal de prótons (∆pH) que, por seu turno, esteve associado com o potencial de fotofosforilação para suportar as necessidades adicionais de ATP sob condições de estresse. O potencial de assimilação do carbono foi decrescido, conforme se deduz da menor atividade da Rubisco (EC 4.1.1.39). As alterações no transporte fotossintético de elétrons afetaram o status redox do estro...

Photosynthetic activity in relation to chlorophylls, carbohydrates, phenolics and growth of a hybrid Salix purpurea × triandra × viminalis 2 at various Zn concentrations

“…The effects included chlorosis, inhibited germination, stunted growth, reduced leaf number and area, reduced yield and reduced flower production. These symptoms are directly connected with plant functioning: such processes as photosynthesis, dysfunction of relevant enzymes, impairment of nutrient uptake, plant wilting and altered water relations (Prasad 2004;Deng et al 2006;Dhir et al 2008). Excess zinc can cause an imbalance in proper functioning of transpiration, photosynthesis and photosynthetic electron transport, as well as biosynthesis of chlorophyll and cell membrane integrity (Richardson et al 1993).…”

Influence of chromium in Laguncularia racemosa (L). Gaertn f. physiology

“…However, studies do not state that the L. racemosa photosynthetic activity is not affected by the impact of chromium in the environment since some species only showed photosynthetic inhibitory effects when exposed to chromium levels higher than 50 mg L -1 (Dhir et al, 2008).…”

“…In L. racemosa, the metabolic tolerance to 0.50 mg L -1 of chromium may be due to partitioning of heavy metals in vacuoles of root cells associated with their low mobility to the leaves (Panda and Choudhury, 2005;Dhir et al, 2008). This behavior is itself an efficient mechanism of tolerance in environments contaminated by heavy metals.…”

Ecophysiological adaptation and metal accumulation in water hyacinth from two tropical rivers

“…Some aquatic plants accumulate metals and many species suffer phytotoxicity (Fritioff and Greger, 2006;Dhir et al, 2008;Li et al, 2008) while others easily grow in the presence of metals. An example is the hyperaccumulator Eichhornia crassipes (Mart.)…”

“…Among chlorophyll a fluorescence parameters, F v /F m rate has been the most widely used to meter different type of stresses (Bolhar-Nordenkampf et al, 1989;Oliveira et al, 2002;Sarijeva et al, 2007;Dhir et al 2008;Lage-Pinto et al, 2008;Paiva et al, 2009). Fluorescence quenchings are also informative tools and the association of the nonphotochemical quenchings data with carotenoids may increase and help to evaluate the plant's life quality.…”