http://www.lcb.esalq.usp.br/publications/articles/2012/2012ppbv56n1p79-96.pdf

Biochemical dissection of diageotropica and Never ripe tomato mutants to Cd-stressful conditions.

Cadmium (Cd) loading in soil and the environment has been accelerated worldwide due to enhanced industrialization and intensified agricultural production, particularly in the developing countries. Soil Cd pollution, resulting from both anthropogenic and geogenic sources, has posed an increasing challenge to soil quality and food security as well as to human health. Compared with other heavy metals such as copper (Cu) and lead (Pb), Cd demonstrates greater mobility along food chain and in the environment. Cd is harmful to human health and potentially toxic to biota at lower concentrations. Therefore, it is imperative to develop management strategies for control of pollution sources and remediation of contaminated soils. Extensive studies have been conducted in recent years to understand biogeochemical processes of Cd in soils, its cycle in agroecosystems, impacts on soil quality and food security, and the remediation of Cd-contaminated soils. Phytoremediation as an emergent technology has stimulated refreshed interest since it is cost effective and ecofriendly, especially the use of metal hyperaccumulating plants to extract or mine heavy metals from contaminated soils. Progress has been made in the understanding of mechanisms that govern Cd accumulation and detoxification in accumulating plants. This review provides recent progress in soil biogeochemistry and plant physiology of Cd, mechanisms of hyperaccumulation of Cd in plant, remediation strategies including chemical and microbiological enhancement, and optimization of field management practices, in the hope to stimulate more research in the future.

Soil Biogeochemistry, Plant Physiology, and Phytoremediation of Cadmium-Contaminated Soils

Cadmium (Cd) is extremely toxic metal and reduces plant growth. Therefore, study was conducted to evaluate the effect of various Cd levels 0, 5, 20, 50 and 80 mg L -1 on seed germination and seedling growth of four wheat cultivars (Sehar-06, Fareed-06, Inqlab-91, Chakwal-50). Cadmium showed toxicity at 5 mg L -1 in case of root and shoot growth whereas 20 mg L -1 in case of seed germination and germination energy which is aggravated on further addition of Cd from 50 to 80 mg L -1 . Sehar-06 performed better under Cd stress while Inqlab-91 had poor performance. Later had maximum decrease in root length (70.4%), shoot length (81.2%), percent germination (68%) and germination index (76.8%) at 80 mg L -1 Cd compared to control. Tolerance index varied among different cultivars, maximum tolerance was observed in Sehar-06 followed by Fareed-06, Chakwal-50 and Inqlab-91. From these results it is evident that cv. Sehar-06 could germinate well on soils contaminated with Cd, however, more studies are required to signify its effects on growth and yield of wheat.

Effect of cadmium on seed germination and seedling growth of four wheat (triticum aestivum l.) cultivars

Eight durum and ten hexaploid varieties were grown in two years. Yields under rainfed and irrigated conditions were used to assess resistance. Among durum wheats, DT367 and Cando had high yields under both environments. Lakota and Pelissier ranked better under rainfed than irrigated conditions, indicating adaptation to dry conditions. Among hexaploids, Echo, Amy and Pitic 62 had high, stable yields, while Canuck showed improved yield rank under rainfed conditions. No varietal differences were detected by measuring diffusive resistance (autoporometer) or leaf temperature (hand-held infrared thermometer screening method). However, there were differences in excised leaf water loss rate. Pelissier had the best water retention capacity. Progeny of Pelissier X Hercules showed retention capacities ranging between parental values. Visual rating of excised leaves identified lines with superior water retention capacities

Evaluation of techniques for screening for drought resistance in wheat.

A greenhouse pot experiment was conducted to study the impact of arbuscular mycorrhizal fungi--Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on the growth, Cd uptake, antioxidant indices [glutathione reductase (GR), ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), ascorbate (ASA), glutathione (GSH) and malonaldehyde (MDA)] and phytochelatins (PCs) production of Lonicera japonica in Cd-amended soils. Gv and Ri significantly increased P acquisition, biomass of shoots and roots at all Cd treatments. Gv significantly decreased Cd concentrations in shoots and roots, and Ri also obviously reduced Cd concentrations in shoots but increased Cd concentrations in roots. Meanwhile, activities of CAT, APX and GR, and contents of ASA and PCs were remarkably higher in Gv/Ri-inoculated plants than those of uninoculated plants, but lower MDA and GSH contents in Gv/Ri-inoculated plants were found. In conclusion, Gv and Ri symbiosis alleviated Cd toxicity of L. japonica through the decline of shoot Cd concentrations and the improvement of P nutrition, PCs content and activities of GR, CAT, APX in inoculated plants, and then improved plant growth. The decrease of shoot Cd concentrations in L. japonica inoculated with Gv/Ri would provide a clue for safe production of this plant from Cd-contaminated soils.

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Can arbuscular mycorrhizal fungi reduce Cd uptake and alleviate Cd toxicity of Lonicera japonica grown in Cd-added soils?

A hydroponics experiment was conducted in the University of Zhejiang Hangzhou, China to investigate the effect of salinity (NaCl) and cadmium (Cd) on root morphology of different wheat cultivars differing in salt tolerance. Cd and NaCl stress inhibited shoot and root dry weight, number of root tips (lateral roots), total root length, root average diameter and total root volume. Increasing concentration of Cd and NaCl had negatively affected root morphology of all cultivars under study. The combined effect of Cd and NaCl on these parameters was more than both Cd and NaCl alone. There was an obvious difference in response to both stresses among the three cultivars with Bakhtawar-92 being less affected.

Effect of cadmium and salinity stresses on root morphology of wheat

The effect of four regimes of irrigation on physiological and morphological characteristics of sunflower hybrids was studied at National Agricultural Research Centre (NARC), Islamabad, Pakistan. The four irrigation levels were control (no-irrigation), heading stage, heading + flowering stages, and heading + flowering + grain filling stages. Sub plot size of 4.5 m x 5 m was maintained and randomized complete block design in split plot arrangement having 5 replications were used. Water regimes/ irrigation were kept in the main plot while hybrids (Parsum-1 and SF-187) in the sub plot. Maximum seed yield (2680 kg ha -1 ) was obtained with three irrigations when compared with other treatments. Among the hybrids, SF-187 produced more yields (2440 kg ha -1 ) than the hybrid Parsun-1 (2333 kg ha -1 ). Oil content was lower (41.01%) in treatments receiving three irrigations. Seed yield with three irrigations was 24.83% higher than the control plot. Maximum leaf area index was observed when irrigation was given at 90 day interval after emergence of the sunflower (third irrigation). The same trend was also observed in dry matter accumulation and crop growth rate.

Effect of irrigation on physiology and yield of sunflower hybrids.

Meristem Culture of Potato (Solanum tuberosum L.) for Production of Virus-Free Plantlets

In situ studies were conducted to assess the morpho-physiological responses of wheat genotypes to PEG-induced water stress. Wheat genotypes were raised in hydroponic cultures where plants were nourished with ½ strength Hoagland solution. Plants were exposed to 00, 10, 20, 30 and 40% PEG-6000 at 4-leaf stage. PEG was applied in split doses @ 10% with an interval of 15 days. Significant differences (p≤0.05) were recorded for all the parameters studied due to genotypes and PEG concentrations. Wheat genotypes showed negative but variable response to PEG concentrations for shoot length, root length, root/ shoot ratio and root mass whereas PEG imposed stress had positive impact on proline content and abscisic acid (ABA). Genotype Khattakwal attained maximum shoot length in PEG induced stress. Maximum root/shoot ratio and root mass was recorded in Ghaznavi-98 while Tatara and Khattakwal attained maximum relative water content. Endogenous proline and ABA content increased up to 10 fold in response to 40% PEG. Maximum proline was accumulated by Khattakwal whereas maximum ABA by ICP-3.

In situ assessment of morpho-physiological response of wheat (triticum aestivum l.) genotypes to drought

The present field studies investigated the effect of the integrated use of mineral N and organic N sources (Farm yard manure, Poultry manure and Filter cake) on maize crop. Field experiment was carried out on silty clay loam soil at NIFA Tarnab Peshawar Pakistan during 2005-06. There were 17 treatments with four replications using maize variety Azam as a test material in RCB design. Statistical analysis of the data revealed that integrated application of organic N sources (farmyard manure, poultry manure, filter cake) and mineral N source (urea) resulted an upward trend in the yield of maize crop. Maximum biomass, (9554 kgha -1 ) and stover yield (8136 kgha -1 ) of maize were obtained from those treatments where 100% (FYM) was used. Maximum grain yield (1838 kgha -1 ) was recorded from treatment where 25% farmyard manure (FYM) and 75% mineral nitrogen source (urea) were used. Agronomic efficiency and nitrogen use efficiency was also found higher in the treatments where 25% N from farmyard manure (FYM) and 75% N from mineral N source (urea) was applied. It was concluded that combination of 75% mineral N source and 25% organic N sources (urea) are the best combination for sustainable yield.

Raziuddin

Papers

Effect of cadmium and salinity stresses on root morphology of wheat

Effect of irrigation on physiology and yield of sunflower hybrids.

Meristem Culture of Potato (Solanum tuberosum L.) for Production of Virus-Free Plantlets

In situ assessment of morpho-physiological response of wheat (triticum aestivum l.) genotypes to drought

Effect of integrated use of nitrogen on yield and n uptake of maize crop