Effects of arsenic on phosphorus content in different organs and chlorophyll fluorescence in primary leaves of soybean

Abstract

The effect of arsenic (32 -96 μM) on the phosphorus content and Chl fluorescence was studied in soybean (Glycine max Merril) grown in the nutrient solution with and without phosphorus. The increased concentration of As led to the decrease in P content in plant organs. Parameters of Chl fluorescence of soybean leaves in the presence of these As concentrations did not show significant changes.Additional key words: Glycine max, photosystem 2, quantum yield. ⎯⎯⎯⎯Pollution of the soil and atmosphere by arsenic (As) is conditioned by the industry development. Copper smelters and thermal plants are great pollutants of the atmosphere. According to Smirnov and Muravin (1977) natural As content in the soil is 5 mg(As) kg -1 (soil). As, an analogue to phosphorus, is absorbed from the soil by P transporters. As inhibits P uptake in barley (Asher and Reay 1979) and Arabidopsis (Dunlop et al. 1997). In many of plant species, arsenates and arsenites have an affinity for thiols, such as glutathione. Furthermore, phytochelatins are formed as a response to As (Schmöger et al. 2000). Hartley-Whitaker et al. (2000a, 2000b confirmed that As-tolerant Holcus lanatus L. had higher phytochelatins concentrations than As-intolerant species. Hence, similar to heavy metals, As also mobilises the socalled nonenzymic antioxidants, such as glutathione, ascorbates, and phytochelatins. In order to investigate As effects on the uptake and distribution of phosphorus (P) in plant organs and chlorophyll (Chl) fluorescence in the soybean leaves, different As concentrations were used: 2.4, 4.8, 6.0, and 7.2 g(As) m -3 , corresponding to 32, 64, 80 and 96 μM As.After the 5-d germination in the dark, plants of soybean (Glycine max Merril. cv. ZP S015) were transferred into pots with the nutrient medium of pH 7.0 (Hoagland and Arnon 1950). Plants were grown in growth chambers at a 12-h photoperiod, irradiance of 300 μmol m -2 s -1 (Sylvania cool white lamp P9GT12-CEW-VHO, Danvers, USA) and day/night temperature of 24/20 °C. Plants grown on the complete medium were the control ones. The P content in the other three variants was half or double of that in the control or zero. Plants grown with and without P were exposed to 32, 64, 80 and 96 μM Na 2 HAsO 4 for 5 d.

Changes in photosynthetic pigments and chlorophyll-a fluorescence attributes of sweet-forage and grain sorghum cultivars under salt stress

“…The decrease of phosphorus, as a key element of intermediates participating in the electron transport, led to reduced ET O /DI O . On the other hand, increasing arsenic decreased TR O /DI O via phosphorus deficiency in soybean [31]. It was related to the vital role of phosphorus in all energy cycles of biosystems [31].…”

“…On the other hand, increasing arsenic decreased TR O /DI O via phosphorus deficiency in soybean [31]. It was related to the vital role of phosphorus in all energy cycles of biosystems [31]. Moreover, TR O /DI O was affected by a combination of zinc absence and drought, which drastically lowered TR O /DI O in maize [27].…”

“…However, DF PSI , DF PSII and DF total describe the redox potential in PSII, PSI and the whole photochemical reactions (total), respectively [15,31]. Total performance indices (PI ABS, total and PI CS, total ) and total driving forces (DF ABS, total , DF CS, total ) evaluate the whole of the photosynthetic apparatus from the first point in PSII toward the end point in PSI [14].…”

“…These indices are based on four factors including the density of the reaction centers per absorption energy flux (RC/ABS), the maximum quantum yield (Φ Po ), the electron transport efficiency from Q A to Q B (Ψ Eo ) and the electron transport efficiency from Q B to the end electron acceptors of PSI (δ Ro ) [14,15,30,31]. In agreement with this finding, Ripley et al [12] reported that the decrease in the PSII performance index (PI ABS, PSII ) of sorghum was in relation to significant decreases in Φ Po , Φ Eo and Ψ Eo .…”

“…If a stressful condition influences one of these factors, performance indices will display variations clearly and distinctly [14,15,30,31]. Due to this advantage, performance indices are used to screen genotypes in different researches [14,15,34].…”